AWUS01 KWNH 270842
FFGMPD
TNZ000-KYZ000-ALZ000-MSZ000-271500-

Mesoscale Precipitation Discussion 0072
NWS Weather Prediction Center College Park MD
441 AM EDT Sat Mar 27 2021

Areas affected...Tennessee

Concerning...Heavy rainfall...Flash flooding likely

Valid 270840Z - 271500Z

Summary...Thunderstorms expected to develop and track over the
region this morning will have the potential to produce hourly
totals up to 2". Through 15Z, 2-3"is possible with some potential
near4" and this is likely to cause some instances of flash
flooding, especially over portionsof middle Tennessee where soils
are more saturated from recent rainfall.

Discussion...In response to a broad area of large scale forcing
for ascent from the right entrance region of a jet streak over the
Ohio Valley and the eventual approach of shortwave energy from the
Plains, a northward advancing warm front through Mississippi and
Alabama this morning will help initiate/focus convection over
portions of Tennessee. The environment will rapidly evolve during
this time with a surge of MUCAPE of 2000-2500 J/kg and a rapid
increase in precipitable water to 1.3-1.4". Dewpoints, currently
in the 40s over TN, will increase well into the 60s this morning.
850 mb flow impinging on the boundary is expected to increase to
around 35 kts. Storms should initiate closer to 12Z and track east/northeasterlyand with the mean flow nearly aligned to the
storm motions, repeating rounds are likely.

The 00Z hi-res guidance shows reasonable agreement for a stripe of
2-3" through about 15Z, particularly across middle Tennessee. The
06Z HRRR shows an uptick in QPF, with localized 3-4" totals
through 15Z in and around the Nashville metro region, which is
concerning. Hourly totals between 1-1.5" are likely at times after
13Z and there is some signal for near 2" totals as seen in the
HRRR. The last several runs of the HRRR have been very consistent
with this signal.

Much of this area is running precipitation surpluses 150-300
percent of normal the last 14 days. The lowest flash flood
guidance is across middle Tennessee where 1-hr FFGs are 1.5". As
such, some instances of flash flooding will be likely after 12Z
and continuing through the remainder of the morning hours.

Taylor

ATTN...WFO...HUN...JKL...LMK...MEG...MRX...OHX...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 36708426 35988383 35098545 34828845 35578922
36288799 36638655

$$
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AWUS01 KWNH 270959
FFGMPD
TNZ000-MSZ000-ARZ000-271557-

Mesoscale Precipitation Discussion 0073
NWS Weather Prediction Center College Park MD
558 AM EDT Sat Mar 27 2021

Areas affected...vicinity of southwest TN

Concerning...Heavy rainfall...Flash flooding possible

Valid 270957Z - 271557Z

Summary...Showers and thunderstorms are beginning to show training
character in this area. Hourly rain totals to 2.5", along with
local amounts to 4", are possible over the next several hours.

Discussion...A weak surface wave appears to be forming in eastern
Arkansas at 09z, which is causing convection to backbuild to some
degree and begin to show training character as of late. Water
vapor imagery shows a weak shortwave approaching from the ArkLaTex
at this time within an environment of diffluence aloft between the
subtropical jet and the southern stream jet. Precipitable water
values are quickly rising towards 1.5" per recent GPS data across
northern MS. Inflow at 850 hPa is out of the southwest at 35
knots per area VAD wind profiles, with effective bulk shear to
match, which is quasi-parallel to the 850-300 hPa wind. This
inflow is importing 2000+ J/kg of MU CAPE into the area.

Forecasts from the 00z GFS show increasing 1000-500 hPa thickness
diffluence in this area, which could support the
formation/continued development of a convective complex, which
sooner or later should try to expand the convective footprint or
possibly forward propagate the activity to the east over the next
several hours into the area of MPD #072. With the thickness
pattern otherwise remaining status quo, the thunderstorm area may
not show much northerly movement this morning. Instability is
expected to envelop this convective complex with time, which may
increase rainfall efficiency. The only piece of mesoscale
guidance to indicate heavy rain in this area over the next several
hours is the 00z Canadian Regional model, which shows 2"+. The
ingredients available support hourly rain totals to 2.5" where
cells train -- problematic in urban areas or otherwise -- and
local amounts in the 4" are considered possible. As two week
precipitation in this area has been 150-200% of normal, soils are
more sensitive than usual, so flash flooding is considered
possible.

Roth

ATTN...WFO...LZK...MEG...OHX...

ATTN...RFC...LMRFC...NWC...

LAT...LON 35988862 35728798 35008873 34279085 34499177
35129101

$$
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AWUS01 KWNH 271945
FFGMPD
TNZ000-MSZ000-MOZ000-ARZ000-280000-

Mesoscale Precipitation Discussion 0075
NWS Weather Prediction Center College Park MD
344 PM EDT Sat Mar 27 2021

Areas affected...Southeast Arkansas

Concerning...Heavy rainfall...Flash flooding possible

Valid 271944Z - 280000Z

Summary...The threat of heavy to excessive rainfall will be
increasing over parts of southeast Arkansas and a small portion of
neighboring states this afternoon.

Discussion...Thunderstorms capable of producing heavy rainfall are
expected to develop over the southeastern part of Arkansas during
the afternoon in an increasingly moist and unstable atmosphere.
Precipitable water value have been slowly climbing to values at or
above 1.5 inches during the morning and early afternoon over far
eastern Arkansas. Low level flow, which was beginning with 850 mb
speeds around 30 kts at 1830Z based on area 88D VAD wind profiles
and 18Z soundings from LZK and SHV, will help to focus and
strengthen low level moisture flux convergence throughout the day
along a moisture gradient/stationary front separating dewpoints in
the upper 60s over southeast Arkansas from dewpoints in the 50s to
near 60 degrees farther north and west.

High resolution guidance has been consistent in advertising the
uptick in convection developing across the area between 20Z and
2230Z across the area and continuing to increase in coverage into
the evening. Current thinking is that rainfall rates may not
initially be high enough to produce more than limited coverage of
flash flooding, but the risk of flash flooding increases
throughout the afternoon and early evening as rainfall
rates/amounts increase and the ground (which is already wet from
previous events) becomes saturated over an increasing area.

Bann

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 36388964 35378969 34319060 33429169 33429320
34469350 35339209 35889108

$$
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AWUS01 KWNH 101231
FFGMPD
FLZ000-GAZ000-101600-

Mesoscale Precipitation Discussion 0097
NWS Weather Prediction Center College Park MD
830 AM EDT Sat Apr 10 2021

Areas affected...Western Florida Panhandle...

Concerning...Heavy rainfall...Flash flooding possible

Valid 101230Z - 101600Z

SUMMARY...Decaying MCS with quick bust of 1-2" totals reaching
areas affected by heavy rainfall yesterday. Rapid inundation is
possible.

DISCUSSION...GOES-E and Regional RADARs depict the leading edge of
squall line crossing the western tip of the FL panhandle
continuing to progress quite quickly. EIR denotes recent warming
of the deepest convection denoting the slow decay of the squall
line has begun in earnest, as instability pool ahead of the line
continues to restrict in size and limit itself strictly to the
Gulf waters were there remains slightly higher moisture and
thermal spread. Forward progression combined with 10-15kts of SSE
flow off the warm Gulf will continue to provide very strong
moisture flux convergence for the next 2-4 hours resulting in
sub-hourly rainfall totals around 1.5-2.5" with the bulk (1-2") in
15-30 minutes). This alone will cause rapid inundation on
non-permeable (ie, urban) grounds, however, recent heavy rainfall
over the last day with broad 3-7" totals (mainly maximized along
the coastal zones of Bay, Gulf and w Franklin counties are more
likely to see enhanced run-off and inundation rapidly given
saturated ground conditions and swollen streams. Still, with the
slow decay and weakening of moisture flux convergence into the
leading edge of the line.

Though the MCV/bookend vorticity center is expected to lift
north-northeast which may slow forward speed ever so slightly to
counter-act some of the reduction of rain rates further east into Liberty/Calhoun counties by late morning hours, as the upstream
squall line crossing Mobile Bay currently, catches the leading
bow.

Gallina

ATTN...WFO...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 30918661 30908518 30658408 30368398 30028405
29538477 29508530 29828559 30038592 30128705
30648717
$$
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AWUS01 KWNH 180909
FFGMPD
FLZ000-181505-

Mesoscale Precipitation Discussion 0110
NWS Weather Prediction Center College Park MD
508 AM EDT Sun Apr 18 2021

Areas affected...portions of the central and northern FL Peninsula

Concerning...Heavy rainfall...Flash flooding possible

Valid 180905Z - 181505Z

Summary...Rainfall rates of 1-2 in/hr and additional rainfall
totals of 2-4 inches are expected to impact portions of the
north-central FL Peninsula over the next 3-6 hours. Given the
expected overlap of additional rainfall with heavy rain that fell
on Saturday, flash flooding will be possible.

Discussion...Loops of GOES 16 infrared satellite imagery through
09Z showed expanding convection over the eastern Gulf of Mexico
with several strong updrafts near 28N 87W, located just north of a quasi-stationary front. An axis of anomalous moisture (90-95th
percentile for mid-April) was located near and north of the
stationary front with precipitable water values ranging from about
1.6 to 1.8 inches (per 00Z RAOBs and GOES 16 derived data). Local
radar data and surface observations also placed an outflow
boundary from earlier storms which has slowed forward movement
into northern Pinellas and Hillsborough counties as of 09Z. The
most recent (08Z) SPC mesoanalysis estimated weak elevated
instability of less than 500 J/kg across the north-central FL
Peninsula with values over 1000 J/kg to the south of the
stationary front.

Over the next 3-6 hours, short term guidance is unanimous with the strengthening of southwesterly low level flow over the eastern
Gulf by about 10 kt into the west coast of FL, with flow riding
atop the boundary, which will help to support increasing
convection beyond 12Z into the FL Peninsula. There is some
uncertainty regarding whether convection will form north of the
outflow boundary, stationary front or both. Despite the cloud
cover, some increase in instability is expected after sunrise
which will help to support enhancement to rain rates. The west to
east oriented surface to 850 mb convergence axis is aligned with
850-300 mb mean-layer winds, which will allow for repeating cell
movement. Rainfall in parts of Levy, Marion, Putnam and Flagler
counties has totaled 3 to 6 inches over the past 24 hours.
Expected overlap of additional heavy rain with rates of 1-2 in/hr
may cause localized flash flooding in these locations, as well any
sensitive urban locations outside of where the 3-6 inches of rain
fell on Saturday. An additional 2-4 inches of rain will be
possible through 15Z.

Otto

ATTN...WFO...JAX...MLB...TAE...TBW...

ATTN...RFC...SERFC...NWC...

LAT...LON 29648117 29618092 29128072 28738049 28498045
28328112 28248210 28098280 27968309 28328316
28858324 29228335 29268337 29418288 29608199
$$
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AWUS01 KWNH 182113
FFGMPD
FLZ000-190230-

Mesoscale Precipitation Discussion 0111
NWS Weather Prediction Center College Park MD
512 PM EDT Sun Apr 18 2021

Areas affected...Northern Florida Peninsula...

Concerning...Heavy rainfall...Flash flooding possible

Valid 182115Z - 190230Z

SUMMARY...Training Cells Capable of 2"+/hr rates and saturated
grounds support possible rapid inundation/flash flooding concerns
through late evening hours.

DISCUSSION...GOES-E WV suite depicts a solid shortwave
south-southeast of the Mouth of the Mississippi River advancing
eastward with broad upper level divergence downstream across the
northeastern Gulf of Mexico. As such, a surface inflection is
enhancing along an SW-NE oriented boundary and enhancing southerly
flow across the West Coast the peninsula with 10-15kt flow
strengthening to 20-25kts from surface to 850mb as the shortwave
approaches. The frontal zone is draped across the Peninsula from
BKV to south of MCO, north of VRB anchored by outflow from earlier
convective outflow.

Within the warm sector, Tds are over 70F though 850-7H LPW
suggests western Atlantic source of drier air...so instability is
sizable with MLCAPEs over 2000 J/kg, suggesting some dry air
entrainment may result closer/south of the frontal boundary, but
still low level inflow would be very moist, so surface based cells
will have ample entrainment to produce some moisture flux
convergence to slowly saturate profiles for increased rainfall
efficiency well after maturity. LPW also denotes a more deeply
saturated environment across the Panhandle and far northern
Florida with deepest moisture of 1.75 to 2" along the frontal
zone/inverted surface trof axis along/ahead of shortwave
height-falls. Deep unidirectional flow north of the surface
boundary along the 850mb trof axis would have greater moisture
availability though instability would have sizable reduction
given the narrower profiles with at most MUCAPE of 1000-1250 J/kg.
As such, a narrow axis from Levy/Citrus county to Flagler/N
Volusia county would be the intersection of best instability and
moisture. Strong convective cores along this axis will have the
capability of producing quick burst (1.25"/15mins per HRRR) rates,
particularly as best forcing and maturity of convective
development occurs nearer to 23-00z along/near NW Florida coast.

Cells should be quick moving but have a training orientation
resulting in rainfall totals of 2-3" are possible but could even
reach 4" in very isolated locations through 03z. If the training
axis remains fairly stable, which current trends suggest given
amplitude of the wave approaching, the axis of heaviest rainfall
may track through areas saturated late last evening with 2-3" from
Marion to Flagler county,resulting in area of greatest risk for
rapid inundation/flash flooding.

Some dry air entrainment could result in cold pools that could sag
the axis south, where ground conditions are a bit better but AHPS
weekly anomalies are well over 300% of normal. NASA SPoRT Soil
Saturation through 0-40 cm are fully saturated across the
Panhandle into northern Florida (over 98%) while below 70% across
the I-4 corridor, though has greater urban settings and more
hydrophobic high-runoff capability. As such, have encompasses
these areas into the area of concern.

Gallina

ATTN...WFO...JAX...MLB...TAE...TBW...

ATTN...RFC...SERFC...NWC...

LAT...LON 30108184 30018122 29288088 28168041 28028106
28158203 28328281 28598287 28888288 29438334
29868352 30058258

$$
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AWUS01 KWNH 231913
FFGMPD
TXZ000-240110-

Mesoscale Precipitation Discussion 0112
NWS Weather Prediction Center College Park MD
312 PM EDT Fri Apr 23 2021

Areas affected...South-Central to Southeast TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 231910Z - 240110Z

SUMMARY...Heavy showers and thunderstorms will be expanding in
coverage and organization going through the afternoon hours. A
combination of some localized training of convection and enhanced
rainfall rates will drive an increasing threat for some flash
flooding.

DISCUSSION...The latest GOES-16 WV suite shows a southern stream
shortwave trough ejecting east out into the southern High Plains
which will be interacting with an increasingly moist and unstable
airmass pooling across south-central to southeast TX in vicinity
of a northward advancing warm front, and this is expected to
result in a widespread area of heavy showers and thunderstorms
over the next several hours.

Already the latest VAD wind profiler data shows a 30 to 40
southerly low-level jet nosing up across areas of south-central to
southeast TX, with a pool of PWs approaching 1.75 inches. In fact,
the latest CIRA-LPW data shows a well-defined and fairly
substantial pool of low-level tropical moisture lifting north out
of the western Gulf of Mexico, and in the 700/500 mb layer there
is a bit of an eastern tropical Pacific moisture connection in
association with the subtropical jet.

The airmass pooling along the aforementioned warm front continues
to destabilize with MLCAPE values approaching 1500 j/kg as a
result of continued solar insolation. As the upstream shortwave
trough approaches over the next couple of hours, there will be a
notable increase in large scale ascent from increasingly divergent
flow aloft. This will be coinciding with an axis of stronger
moisture convergence/forcing along the front and should result in
a significant increase in the coverage and organization of
convection.

Given the available moisture transport and rather high PW
environment, the rainfall efficiency should be quite high, with
some hourly rainfall amounts of 2 to 2.5 inches possible, and
especially with the more organized and deeper convective cores in
time.

The latest HRRR and experimental WoFS guidance support a
likelihood for the convection to gradually organize along and just
north of the front and take on some training characteristics with
a cell motion increasingly off to the east-northeast. The training
set-up will favor some very heavy rainfall totals. The latest HRRR
guidance supports as much as 3 to 5 inches of rain with isolated
heavier amounts going through 00Z. This will increase the threat
for at least some flash flooding as a result over the next several
hours.

Orrison

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31639422 31479378 31119365 30659384 30269462
29779652 29629774 29659827 30019846 30549791
31049690 31369597 31599504
$$
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AWUS01 KWNH 111724
FFGMPD
LAZ000-ARZ000-TXZ000-OKZ000-112323-

Mesoscale Precipitation Discussion 0171
NWS Weather Prediction Center College Park MD
123 PM EDT Tue May 11 2021

Areas affected...Eastern Texas...Northwest Louisiana

Concerning...Heavy rainfall...Flash flooding possible

Valid 111723Z - 112323Z

Summary...Scattered to widespread thunderstorms this afternoon
will be capable of producing heavy rainfall and could lead to
flash flooding.

Discussion...Visible satellite early this afternoon shows clearing
pocket developing across portions of eastern Texas and
western/northwest Louisiana while a surface analysis depicts a
boundary inching northward. Water vapor imagery shows a weak
shortwave trough moving through Texas. The environment ahead of
this approaching shortwave is warm and unstable with the mid 70
dewpoints in place contributing to the 2500 J/kg MLCAPE in the
latest mesoanalysis. PWs are above normal in the 1.5-1.7" range.
The combination of the low level convergence with the nearby front
and the large/broad upper divergence ahead of the approaching wave
will the lift needed to initiate convection this afternoon.
Upstream more organized thunderstorms are expected to fill into
the area as well leading to multiple boundary interactions and
cell mergers.

Forecast confidence isn't high on how the scenario will evolve but
the latest thinking and favored hi-res guidance is for the more
discrete cells in the warm sector to grow upscale and more
organized ahead of the line coming in from the west. Some
backbuilding or repeating rounds will be possible. The environment
supports some hourly totals near 2" though as cold pool processes
take over, there should be a decent forward motion to the line
segments later this afternoon which may limit the residence time
for heavy rainfall over any particular location. Portons of the
area have been running above normal precipitation departures with
soil moisture in the 0-40 cm layer above 80-90 percent. As a
result, some instances of flash flooding will be possible.

Taylor

ATTN...WFO...EWX...FWD...HGX...LCH...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 33719599 33609405 32879301 31719332 30659493
30399709 31319832 33059734
$$
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AWUS01 KWNH 192044
FFGMPD
LAZ000-ARZ000-200130-

Mesoscale Precipitation Discussion 0209
NWS Weather Prediction Center College Park MD
443 PM EDT Wed May 19 2021

Areas affected...Arkansas

Concerning...Heavy rainfall...Flash flooding possible

Valid 192042Z - 200130Z

Summary...Flash flooding is possible over portions of Arkansas
during the late afternoon and early evening as broad south to
southeast flow continues to draw moisture into the region.
Western and central portions of Arkansas received 2 to 5 inches of
rain last night/early this morning....making it more susceptible
to additional flooding concerns this evening.

Discussion...Convection over parts of Louisiana and Arkansas was
becoming more numerous and more capable of producing locally heavy rainfall..especially across the central portion of the state where
storms were developing on the nose of a 2.00 inch precipitable
water plume and where southeasterly flow was tapping an airmass
with MUCAPE values of 1000 to 1500 J per kg. Atfernoon VAD Wind
Profiles across the region show that the flow has backed and
accelerated to 25-35 kts at 850 mb since the 12Z soundings...and
that flow has been providing plenty of additional moisture
transport into the region. Flash flooding is possible wherever
convective activity occurs over areas of central and western
Arkansas which received 2 to 5 inches of rain last night/early
this morning.

Present indications are that the probability of rainfall exceeding
1 inch per hour should diminish shortly after 20/00Z as the lower
atmosphere begins to stabilize.

Bann

ATTN...WFO...JAN...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 36179213 35419128 33469137 32799252 33259324
34329346 35429333 35889299
$$
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AWUS01 KWNH 201757
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-202355-

Mesoscale Precipitation Discussion 0216
NWS Weather Prediction Center College Park MD
156 PM EDT Thu May 20 2021

Areas affected...Louisiana...Far Southeast Arkansas...Far Eastern
Texas

Concerning...Heavy rainfall...Flash flooding likely

Valid 201755Z - 202355Z

Summary...Flash flooding is likely this afternoon across much of
Louisiana, far southeastern Arkansas, and far eastern Texas with
rainfall rates increasing to 2-3"/hr. Additional accumulations are
expected to reach 3-6" where showers and thunderstorms train.

Discussion...Convective activity along the LA Gulf coast is
expected to increase this afternoon as SB CAPE ramps up to
1000-2000 J/kg amid peak solar insolation. An exceptional moist
air mass remains in place with PWATs ranging from 1.75-2.00
inches, at or above the 90th climatological percentile for
surrounding WFOs. Efficient low-level moisture transport from the
Gulf will continue with a 25-35 kt 850 mb jet over the region.
Mid- to upper-level forcing continues to be the limiting factor at
play today, but the highly moist and unstable air mass within a
corridor of persistent low-level confluence will keep excessive
rain potential elevated.

The latest radar trends and hi-res CAM guidance suggest that the
ongoing convection across southeastern Louisiana this morning will
begin to shift westward into west-central Louisiana and
neighboring portions of Arkansas and Texas. As instability
increases, expect hourly rainfall rates to increase to the
2-3"/hour range. Training of these rates will allow for 3-6"
totals across an already highly saturated area. 3-hr FFG values
are less than 3 inches across the highlighted area, and even less
than 2 inches across much of Sabine River basin (from Port Arthur,
TX to near Shreveport, LA). Therefore hydrologic sensitivity is
quite high, as NASA SPoRT 0-40 cm soil moisture anomalies exceed
the 90th percentile.

Churchill

ATTN...WFO...JAN...LCH...LIX...SHV...

ATTN...RFC...LMRFC...WGRFC...NWC...

LAT...LON 33519411 33099197 31289109 30149019 28999106
29689384 31529419
$$
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AWUS01 KWNH 232046
FFGMPD
TXZ000-240000-

Mesoscale Precipitation Discussion 0225
NWS Weather Prediction Center College Park MD
445 PM EDT Sun May 23 2021

Areas affected...south/southeast Texas

Concerning...Heavy rainfall...Flash flooding possible

Valid 232039Z - 240000Z

Summary...A persistent south-southeasterly flow regime will
continue to support showers and a few thunderstorms across the
discussion area this evening along with a risk of flash flooding.

Discussion...A persistent, deep south-southeasterly flow regime
continues between the southwestern periphery of a mid/upper ridge
centered over the Mid-South and a weak mid-level vort max centered
about 100 mi E of Brownsville. The flow pattern is continuing to
support a very moist, weakly buoyant airmass across the discussion
area with 2-2.2 inch PW values and 1000-1500 J/kg MUCAPE. The
airmass is weakly capped, and subtle lift associated with the
mid-level vort max and weak/subtle boundary layer confluence
continues to support areas of showers with embedded thunderstorms.
A couple of bands of heavier precipitation exist from near
Gonzales to Victoria, Texas and across the western Houston Metro
area, with enhanced rainfall rates of near 1-2 inches per hour
noted in the western-most band near Gonzales.

This persistent precipitation regime is expected to continue for
at least the next 3 hours or so as southeasterly low-level flow
maintains very moist low-level air and the mid-level vort max is
very slow to move. This will allow for occasional/isolated bands
of heavier precipitation to fall in areas that have received
abundant rainfall over the past week - exceeding 15 inches in a
few spots. The precipitation is resulting in wet soils and
correspondingly low flash flood guidance as a result (as low as 1
inch-per-hour thresholds near PSX/VCT). Additionally, showers and
isolated thunderstorms currently offshore (east of the mid-level
vort max) will migrate inland into the discussion area over the
next 2-3 hours. Most CAMs suggest a downtick in precipitation
rates after around 00Z or so, and the risk of additional flash
flooding will be re-evaluated around that time.

ATTN...WFO...CRP...EWX...FWD...HGX...

ATTN...RFC...WGRFC...NWC...

LAT...LON 30819714 30719608 30209510 29629472 29049495
28459619 28379715 28799794 29199814 29829821
30279811 30599783
$$
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AWUS01 KWNH 251918
FFGMPD
TXZ000-260115-

Mesoscale Precipitation Discussion 0236
NWS Weather Prediction Center College Park MD
317 PM EDT Tue May 25 2021

Areas affected...Eastern TX

Concerning...Heavy rainfall...Flash flooding possible

Valid 251915Z - 260115Z

SUMMARY...Showers and thunderstorms with heavy rainfall rates may
pose some flash flood threat over the next few hours.

DISCUSSION...The latest radar imagery shows a long-lived MCS now
bowing into areas of eastern TX. The airmass out ahead of this
over the broader southeast TX coastal plain is quite moist and
unstable with PWs of 1.8 to 2 inches and MLCAPE values locally
over 2000 j/kg. Meanwhile, a southerly low-level jet of 30 kts is
in place ahead of the MCS.

This favorable thermodynamic environment downstream of the MCS
suggests the ongoing activity will continue to expand off to the
east with some upside potential to expand in coverage and gain
greater convective organization given the additional
destabilization of the boundary layer that is expected over the
next couple of hours due to solar insolation.

Dual-pol radar QPE has already been suggesting some 1.5+ inch/hr
rainfall rates, and these rates should continue within the
stronger cells over the next few hours given the efficient
moisture transport pattern. The radar imagery also shows scattered
heavy showers and thunderstorms developing ahead of the main
complex within the moist/unstable low-level flow with locally
enhanced rain rates.

Over the next few hours, the southern portion of the long-lived
MCS may begin to slow its advance off to the east and may tend to
become oriented more southwest/northeast in nature such that
individual cells may begin to train over the same area. This
coupled with some cell-merger potential will tend to increase the
threat for some excessive rainfall totals going through the
late-afternoon and early evening hours.

The latest HRRR guidance suggests at least locally 3 to 4+ inch
rainfall totals going through 00Z. Given the wet antecedent
conditions, and heavy short-term rainfall rate potential, there
will be at least some concern for flash flooding.

Orrison

ATTN...WFO...FWD...HGX...LCH...SHV...

ATTN...RFC...WGRFC...NWC...

LAT...LON 31999435 31759401 31279389 30589444 30069531
30079603 30289639 30439657 30589667 30799673
30999656 31409561 31949499
$$
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AWUS01 KWNH 271708
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-272305-

Mesoscale Precipitation Discussion 0245
NWS Weather Prediction Center College Park MD
105 PM EDT Thu May 27 2021

Areas affected...Northeast OK...Southeast KS...Southwest MO...Far
Northwest AR

Concerning...Heavy rainfall...Flash flooding likely

Valid 271705Z - 272305Z

Summary...Scattered areas of flash flooding will be likely across
portions of the Southern Plains this afternoon as deep convection
blossoms within a broad unstable warm sector. Hourly rainfall
rates of 2-3" are expected with 6-hr localized accumulations of
4-6 inches possible where convection trains.

Discussion...A broad warm sector characterized by MUCAPE of
2000-4000 J/kg, PWATs of 1.6-1.9 inches, and significant deep
layer moisture convergence will foster rapid upscale growth of
convection across the Southern Plains this afternoon as a potent
mid-level shortwave digs southeastward from the Northern Plains.
Semi-discrete thunderstorms will initially be relatively slow
(15-20 kts) with 2-3"/hr rainfall rates quickly saturating soils.
Much of the highlighted area is already in the 60-90th percentile
of 0-40 cm soil moisture (via NASA SPoRT Land Info System data),
indicating somewhat vulnerable antecedent hydrologic conditions.

Given that the latest high-res CAM guidance (including the HRRR)
has continued to handle convective trends rather poorly,
confidence in any targeted specific area is somewhat low. Where repeating/training of convection can occur 2-3" hourly rates will
rapidly translate to localized totals of 4-6 inches. Some
preference is given to northeastern Oklahoma to realize the
highest rainfall totals, but this area is also where 6-hr FFG is
the highest (3-5 inches). While southeast Kansas in particular has
the lowest FFG (2-4 inches), less repeating of convection is
likely as the advancing cold front cuts off avaliable instability.
That said, the combonation of a highly favorable mesoscale
enviorment and relatively poor hydrologic conditions make
localized flash flooding likely over the broader region.

Churchill

ATTN...WFO...EAX...ICT...LSX...LZK...OUN...SGF...TOP...TSA...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NWC...

LAT...LON 39059479 38889350 38389241 36129320 35379462
35469789 37119753 37999677 38519579
$$
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AWUS01 KWNH 011904
FFGMPD
MSZ000-LAZ000-ARZ000-TXZ000-012300-

Mesoscale Precipitation Discussion 0263
NWS Weather Prediction Center College Park MD
303 PM EDT Tue Jun 01 2021

Areas affected...Eastern TX...Southern AR...North/Central LA

Concerning...Heavy rainfall...Flash flooding possible

Valid 011900Z - 012300Z

Summary...Showers and thunderstorms will continue to blossom
across eastern TX into southern AR and much of LA through the
afternoon. Some of this activity will be slow moving and with the
potential for training over the same areas. Therefore, rain rates
in excess of 2 inches/hour are possible with areal average
rainfall of 2-4+ inches possible through the next six hours.
Antecedent conditions combined with high resolution model signals
suggest flash flooding is possible.

Discussion...A mid/upper level trough across the central U.S. will
continue to provide modest divergence aloft. This combined with
shortwave activity (including an eastward advancing MCV in
northeastern TX) will lead to large scale forcing for ascent. In
response, rich Gulf moisture will be pulled north into eastern TX
and the Lower MS Valley region ahead of a stationary surface
boundary. As a result, precipitable water values of 1.5-1.75
inches will expand east and increase with strong WAA. Despite
morning cloud debris from earlier convection, MUCAPE has already
climbed above 2000 J/kg with additional destabilization expected
over the next several hours. Given these factors, anticipate
convection will continue to develop and blossom within this
region. Based on the propagation vectors and mean wind,
anticipate convection to be slow moving initially with the
potential for brief training. It should also be noted that with
weak shear of around 25 knots, highly organized convection is not
expected but possible across portions of eastern LA by later this
afternoon. According to high resolution guidance, rain rates may
exceed 2 inches/hour with areal average precipitation of 2-4+
inches within the next six hours. This is supported by the higher
HREF probabilities.

While flash flood guidance values within this region are fairly
high (3-5 inches in 3 hours), portions of the ArkLaTex region has
observed above normal precipitation over the past week along with
slightly above normal soil moisture within the scalloped region.
Therefore, scattered flash flooding may occur.

Pagano

ATTN...WFO...HGX...JAN...LCH...LZK...SHV...

ATTN...RFC...ABRFC...LMRFC...WGRFC...NWC...

LAT...LON 34449293 33279115 31199173 30109333 30069533
30649632 31599495 33329448
$$
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AWUS01 KWNH 031556
FFGMPD
VAZ000-NCZ000-SCZ000-032154-

Mesoscale Precipitation Discussion 0270
NWS Weather Prediction Center College Park MD
1155 AM EDT Thu Jun 03 2021

Areas affected...NC/SC

Concerning...Heavy rainfall...Flash flooding possible

Valid 031554Z - 032154Z

Summary...Convection is rapidly expanding in coverage across
portions of the Carolinas, with isolated to scattered flash
flooding possible through the afternoon hours.

Discussion...Broadly confluent flow in the low levels, along with
the upper trough to the west and a subtle wave moving into the SC
coast are all helping initiate convection across SC/NC. The
scattered to widespread nature of convection will probably cap the
amount of destabilization possible...although still looking at
1000-2000 J/kg of CAPE, certainly sufficient for deep convection.
PWs are approaching 2", which is getting close to the early June
maximum expected values. Merging moisture plumes, one in the
mid/upper levels associated with the approaching trough, and the
other in the lower levels off the Atlantic, are supporting the
deep moist profiles. The combination of high PWs, high wetbulb
zero heights, and thin CAPE profiles certainly supports efficient
rainfall in any heavier cells through the afternoon hours.

The area is currently in drought conditions, although heavy rain
yesterday has saturated the top levels of soil in parts of the
region...while the deeper soil anomalies generally remain below
average. So while the region could generally still use more
rain...the saturated top layers of soil should help increase
runoff today resulting in isolated to scattered instances of flash
flooding. Cells will be quick moving off to the northeast, but
unidirectional flow supports some small linear training segments,
and some repeat of cells through the afternoon given the scattered
to widespread nature of convection.

Thus while a more widespread/organized convective complex seems
unlikely, the above ingredients should be enough to still result
in pockets of flash flooding through the afternoon hours. Urban
and low lying areas will be most susceptible...but some flash
flooding is possible wherever todaty's heavier totals overlap with
yesterdays.

Chenard

ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...

ATTN...RFC...MARFC...SERFC...NWC...

LAT...LON 36737652 36407642 35557699 34747755 34497808
34047898 33587939 33427980 33358015 33588039
34218065 34718054 35757932 36517791
$$
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AWUS01 KWNH 081557
FFGMPD
MAZ000-VTZ000-CTZ000-NYZ000-NJZ000-PAZ000-082156-

Mesoscale Precipitation Discussion 0300
NWS Weather Prediction Center College Park MD
1157 AM EDT Tue Jun 08 2021

Areas affected...northeastern Pennsylvania into southern New York
State

Concerning...Heavy rainfall...Flash flooding possible

Valid 081556Z - 082156Z

Summary...Slow-moving storms will pose a risk for isolated flash
flooding through the afternoon and early evening in and near the
discussion area.

Discussion...A slow-moving cluster of convection has evolved in
northeastern Pennsylvania over the past hour or so, with areas of
towering cumulus across much of the discussion area from
southeastern Pennsylvania to western Massachusetts. The storms
are in an environment characterized by weak, but westerly vertical
shear and very strong instability (as high as 4000 J/kg SBCAPE in
areas downstream of ongoing storms). The pre-convective airmass
is quite moist also, with PW values of 1.6 to 1.9 inch areawide.
Lift from an approaching shortwave trough across central PA/NY and
weak/subtle boundary layer confluence was also providing ascent
aloft for thunderstorm development.

Latest observations/guidance suggests that this mainly diurnally
driven convective activity will continue to expand in coverage
this afternoon. Local rainfall rates of 1-2 inches per hour have
already been observed beneath convective cores, and this will
expand in coverage with time - especially as storms form mature
cold pools and propagate slowly eastward. Flash flood guidance
values are in the 0.75-1.5 inch-per-hour range, which should be
easily exceeded beneath heavier convective cores/clusters. The
threat should wane some after sunset with loss of
heating/surface-based instability.

Cook

ATTN...WFO...ALY...BGM...BOX...CTP...OKX...PHI...

ATTN...RFC...MARFC...NERFC...NWC...

LAT...LON 43057325 42817261 42157246 41557285 40927380
40337472 40037588 40107668 40307712 40607717
42347608 42697525 43017412
$$
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AWUS01 KWNH 081911
FFGMPD
OHZ000-MIZ000-INZ000-082315-

Mesoscale Precipitation Discussion 0302
NWS Weather Prediction Center College Park MD
311 PM EDT Tue Jun 08 2021

Areas affected...Northwest OH...Northeast IND...Ext Southwest MI.

Concerning...Heavy rainfall...Flash flooding possible

Valid 081910Z - 082315Z

SUMMARY...Slow moving cells and deepening moisture profiles
support localized heavy rainfall and potential for flash
flooding...

DISCUSSION...GOES-E WV suite denotes older shortwave/closed low
feature over the Tri-State area of S MI/NW OH/NE IND. Given its
placement in the larger scale pattern, upper level flow is
favorable for solid diffluence to support the developed convection
in/east of the UL proper. CIRA LPW suite also denotes moisture
entering the low to middle profile of the cells to further enhance
the rainfall efficiency, resulting in 1.75 to 1.9" of total
moisture in the column. Entrainment with 15-20kts of flow through
85-7H brings rates to 2-2.25"/hr, though equally allows for slow
cell motions and with upstream inflow and upstream propagation to
further slow motions. Strongest overshooting top near Hancock
county, OH seems to be ideally situated for this combination of
favorable upper-level divergence to show signs of building back
against the flow slightly. Development is enhanced by solid low
level convergence along Lake enhanced boundaries intersecting with
the weak northward march of the higher Td air from the
Ohio/Mississippi Valleys.

While the area is generally below average in the longer terms...
there is lower FFG values across the area of concern which aligns
with with AHPS 2-week anomalies near to 200% of normal. Hourly
FFGs of 1-1.5" and 3hr values of 1.5-2.5" have solid potential to
be exceeded with these cores. But given the nature of the complex
overall coverage should be scattered in nature and will dissipate
with reducing instability into the evening. As such, flash
flooding is considered possible but local thunderstorms of 2-3"
totals in 1-2 hours or even sub-hourly per report near Vermilion.

Gallina

ATTN...WFO...CLE...DTX...ILN...IWX...

ATTN...RFC...NCRFC...OHRFC...NWC...

LAT...LON 42358328 41698290 41558155 41128142 40638193
40448272 40538339 40938435 41008536 41398551
41748465
$$
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AWUS01 KWNH 091505
FFGMPD
TNZ000-ALZ000-MSZ000-ARZ000-092102-

Mesoscale Precipitation Discussion 0312
NWS Weather Prediction Center College Park MD
1104 AM EDT Wed Jun 09 2021

Areas affected...northern Mississippi, eastern/southeastern
Arkansas, northwestern Alabama

Concerning...Heavy rainfall...Flash flooding likely

Valid 091502Z - 092102Z

Summary...Areas of flash flooding remain likely across the
discussion area through at least 21Z. Significant impacts are
expected given extreme antecedent rainfall over the past 24 hours.

Discussion...Recent radar mosaic imagery indicates several bands
of slow-moving/propagating convection across the discussion area -
particularly in eastern Arkansas, northern Mississippi (near
Oxford), and northern Alabama (northwest of Birmingham). The location/orientation of these bands isn't particularly surprising
given broadly confluent westerly/southwesterly 850mb flow
partially orthogonal to a weak low-level boundary from near Little
Rock to near Tupelo. The low-level flow was maintaining a moist,
destabilizing pre-convective airmass across the region
(characterized by 2-inch PW values, nearly 2000 J/kg MUCAPE, and
minimal convective inhibition). The moisture and instability was
promoting rainfall rates of up to 3 inches per hour beneath
heavier thunderstorm cores which easily exceed FFG thresholds in
the region - especially in eastern Arkansas and northern
Mississippi where widespread areas of 3-10 inches of rainfall were
observed yesterday. Impressive MRMS Flash responses have already
been noted this morning in east-central Arkansas and near Oxford,
Mississippi.

Though the general axes of convergence are less focused compared
to yesterday, models/observations generally suggest that bands of
heavy rainfall will continue to propagate slowly
eastward/east-southeastward resulting in very heavy rainfall and
additional accumulations of at least 2-4 inches (locally higher)
through 2030Z. Models also indicate initiation of convection
south of these bands, which isn't surprising given the strong
destabilization occurring there. Localized training of convection
is expected in this regime (which may already be materializing in
east-central Arkansas). Convective mergers may also allow for a
slow, more southward component to MCS motions during the period as
well, allowing for heavier precipitation to eventually shift
toward the US82 corridor in Mississippi. Each of the
aforementioned factors point to locally significant flash flooding
especially beneath heavier/training convection.

Cook

ATTN...WFO...BMX...HUN...JAN...LZK...MEG...OHX...

ATTN...RFC...ABRFC...LMRFC...SERFC...NWC...

LAT...LON 35068996 35018783 34828659 34608618 34118614
33568659 33268805 33139020 33109190 33399234
34059232 34689205 34949122
$$
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AWUS01 KWNH 091732
FFGMPD
NYZ000-PAZ000-WVZ000-OHZ000-092331-

Mesoscale Precipitation Discussion 0314
NWS Weather Prediction Center College Park MD
132 PM EDT Wed Jun 09 2021

Areas affected...Virginia, northern North Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 091731Z - 092331Z

Summary...Convection drifting slowly southward across the
discussion area could pose a very localized/isolated flash flood
risk through peak-heating hours..

Discussion...Satellite/lightning imagery indicates scattered
thunderstorms across the discussion area that were moving slowly south-southwestward. The cells were in an environment
characterized by very weak vertical wind shear (with northerly
flow around 10 knots or so from the surface to 300mb), moderate
instability (around 2000 J/kg MLCAPE), and PW values ranging from
1.3-1.7 inch. These conditions are conducive for brief heavy
downpours with as much as 1 inch per hour of rainfall in a few
spots. FFG values of around 1.5 inch-per-hour rainfall rates
(slightly lower in southern New York State and southwestern
Pennsylvania) suggest that a brief/isolated flash flood risk will
exist - particularly in areas where heavier rainfall occurs over
flood-prone or hydrophobic surfaces (i.e., urban areas and hilly
terrain). This risk should be mainly dirunally driven and lessen
after sunset.

Cook

ATTN...WFO...BGM...BUF...CLE...CTP...PBZ...

ATTN...RFC...MARFC...NERFC...OHRFC...NWC...

LAT...LON 42317939 42297756 41927676 41567661 40907664
40347684 39847756 39977979 40688129 41208142
41688113
$$
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AWUS01 KWNH 101620
FFGMPD
NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-WVZ000-102215-

Mesoscale Precipitation Discussion 0321
NWS Weather Prediction Center College Park MD
1219 PM EDT Thu Jun 10 2021

Areas affected...portions of the northern Mid-Atlantic region

Concerning...Heavy rainfall...Flash flooding likely

Valid 101616Z - 102215Z

SUMMARY...Slow moving thunderstorms are expected to increase in
coverage across the northern Mid-Atlantic region this afternoon.
Rainfall rates of 1-2 in/hr will be common, but locally higher
rates can not be ruled out.

DISCUSSION...Visible satellite imagery through 1545Z showed an
expanding cumulus field within an otherwise mostly clear
environment across the Delmarva Peninsula into MD and southeastern
PA. A few showers and thunderstorms have also popped up on
regional radar imagery over northern Delaware Bay and along the
Catocin Mountains of northern MD into the Appalachian chain of
southern PA. PWATs within the pre-convective environment are 1.7
to 2.0 inches and 850-200 mb mean-layer flow is very weak across
the entire region at less than 10 kt, which will support slow
storm motions. Little CIN on the 12Z soundings from WAL and IAD
suggest storm coverage will continue to increase with daytime
heating with the front and local terrain acting as sources for
lift. In addition, locally stronger easterly flow just behind the
cold front may help to support near-stationary convection along
the terrain of northern VA into northwestern MD and southern PA.

Given the lack of speed shear with height, storms should not be
organized in nature or long-lasting, but they should be rather
efficient with rainfall production given high wet bulb zero
heights of roughly 13 kft. Rainfall rates of 1-2 in/hr are very
likely with localized rainfall rates up to 3 in/hr possible. In
fact, rainfall rates from the HRRR support 1-2 inches of rain in
15 to 30 minutes which seems reasonable given the moist
environment. Portions of the Delmarva into southern MD and
southeastern PA received heavy rainfall yesterday and will be more
susceptible to localized flash flooding today. While flash
flooding is not expected to be widespread across the entire
region, scattered to numerous slow moving thunderstorms will
produce heavy rainfall with several areas at risk for flash
flooding, including the urban I-95 corridor from south of D.C.
into northern DE with 2-4 inches expected through 22Z.

Otto

ATTN...WFO...AKQ...CTP...LWX...PBZ...PHI...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 40587854 40517767 40357679 40047594 39547543
38187496 37767548 37877657 39167880 39907971
40507942
$$
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AWUS01 KWNH 101727
FFGMPD
MSZ000-LAZ000-ARZ000-102315-

Mesoscale Precipitation Discussion 0322
NWS Weather Prediction Center College Park MD
127 PM EDT Thu Jun 10 2021

Areas affected...central AR into northeastern LA and central MS

Concerning...Heavy rainfall...Flash flooding likely

Valid 101722Z - 102315Z

SUMMARY...Backbuilding and training convection is expected to
continue areas of flash flooding for central MS and northeastern
LA, expanding northwestward into central AR through early evening.
Peak rainfall rates of 2-3 in/hr should continue and the overlap
with recent areas of heavy rain will exacerbate ongoing flooding.
An additional 3-5 inches is forecast through 23Z.

DISCUSSION...A long-lived complex of thunderstorms over the Lower
Mississippi Valley has shown a slow evolution over the past 6
hours toward the south and west. Low level cloud elements on
visible imagery continue to show a confluent pattern into the
tri-state region of AR/LA/MS where MRMS rainfall estimates ending
at 17Z have been near 4 in/hr in Issaquene County. A lack of
rainfall observations in the area has made it difficult to confirm
MRMS estimates, but the history of this complex and the efficient
environment make the MRMS rates seem reasonable. MLCAPE estimates
as of 17Z show 2000-3500 J/kg over northern LA into central AR
where mostly clear skies have allowed surface temperatures to
climb into the upper 80s while dewpoints are in the mid to upper
70s.

While winds at 850 mb have weakened since earlier this morning
into the 10-20 kt range, similar strength and direction of the
850-300 mb mean flow has supported backbuilding of storms into
southeastern AR. Short term forecasts from the RAP have been
consistent with maintaining the current strength and direction of
the low and mid-level flow into the early evening. Therefore, weak
to locally moderate low level confluent flow within the moist
environment and the presence of the right-entrance region of a
40-60 kt upper level jet streak to the north should continue to
support convective development over the next several hours.

Ongoing training near the LA/AR/MS junction may weaken in the next
2-3 hours in favor of increasing development into a expanding
cumulus field over central AR. The greatest confidence for an
additional 3-5 inches of rain exists across far western MS into
northeastern LA and southern AR, while convection to the north
(centarl AR) is expected to be more scattered in nature with
rainfall rates of 1-2 in/hr. Given heavy rain over the past 3
days, additional any added heavy rain will only worsen ongoing
flooding concerns.

Otto

ATTN...WFO...JAN...LZK...MEG...SHV...

ATTN...RFC...ABRFC...LMRFC...NWC...

LAT...LON 35689213 35289148 34019055 33468979 33018917
32418911 32098970 32089100 32769240 33579289
34879299 35589275
$$
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AWUS01 KWNH 101802
FFGMPD
MDZ000-VAZ000-WVZ000-OHZ000-KYZ000-102300-

Mesoscale Precipitation Discussion 0323
NWS Weather Prediction Center College Park MD
201 PM EDT Thu Jun 10 2021

Areas affected...WV...southwest OH...Western & Southwestern VA...

Concerning...Heavy rainfall...Flash flooding possible

Valid 101800Z - 102300Z

SUMMARY...Slow/Chaotic motions but ample deep warm cloud layer for
efficient rainfall through complex terrain.

DISCUSSION...GOES-E WV and Visible suite depict a vertically
sheared cyclone with 6.2um channel centered over western VA, 7.3
over central WV and IR/VIS channels showing compact center into
southwest OH. As a result, there is weak chaotic flow regimes,
though low level through 7H suggests southwesterly moist flow
across E WV into the front ranges of the Appalachians in western
VA and this is denoted well in the 850-7H Layer PW from CIRA.
Being on the western periphery of the upper-level waves has
supported some additional clearing for ample isolation and
building of instability. Mtn/Valley circulation combined with
some low level mass piling is supporting increasing agitation of
cu field both under the best mid-level cooling/upper-low but also
along the southeast quadrant of the lower circulation along/near
the Ohio River. Mid-level cloudy conditions have all but rendered
areas across far N WV into the western MD/Eastern WV panhandle
less conducive.

Deepest convective elements are forming with the better mid-level
lapse rates along the terrain of far E KY into W VA. Still, due
to deep warm cloud layer, ample moisture individual cells will be
highly efficient with up to 2"/hr rates. Cell motions will be
near zero further north and west with 5-10 kts toward the NNE
across southern portions of the MPD area. Hi-Res CAMs all suggest
best scattered 2-2.5" totals over E WV into W VA with the slightly
better 5-10 kts of inflow to help maintain updrafts more than the
"up and splat" nature further north and east,
propagating/regenerating along the outflows.

Still both modes have solid potential to exceed the low FFG in
complex terrain which is about 1"/hr though lower values of
.5-.75"/hr are nearer the low level cyclone convergence point.
Flash flooding is likely though it will be highly
scattered/locally focused to only a few watersheds...where some
neighboring watersheds may miss out totally.

Gallina

ATTN...WFO...JKL...LWX...MRX...PBZ...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC...

LAT...LON 39598200 39578099 39458008 39277949 39047903
38157928 37377979 36738086 36788232 37348272
38158231 39158235
$$
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AWUS01 KWNH 191152
FFGMPD
FLZ000-GAZ000-ALZ000-MSZ000-191800-

Mesoscale Precipitation Discussion 0352
NWS Weather Prediction Center College Park MD
751 AM EDT Sat Jun 19 2021

Areas affected...southern Alabama, western Florida Panhandle,
southeastern Mississippi

Concerning...Heavy rainfall...Flash flooding likely

Valid 191149Z - 191800Z

Summary...An axis of focused convergence just east of the center
of TS Claudette will promote areas of flash flooding in the
discussion area (southeastern Mississippi through the Florida
Panhandle) through at least mid-day.

Discussion...Latest observations/mesoanalysis shows an area of
focused low-level convergence across southwestern Alabama and
vicinity coincident with intense convective development. The
storms themselves are in a very moist/buoyant environment with PW
values of 2.1-2.4 inches and 2000 J/kg MLCAPE values - highest
nearer the coast. The airmass is promoting extremely efficient
rainfall rates of 2-3.5 inches per hour near the strongest
convection - including within a dominant convective band near
Mobile this morning and with scattered cells ahead of the band
that will move northward into and through the discussion area from
open Gulf waters. 2-4 inch rainfall totals have already been
noted in southeastern Mississippi/southern Alabama - with
localized instances of totals nearing 8 inches since midnight CDT.

Although the specific evolution of convective bands within this
regime is somewhat uncertain, models and observations generally
suggest that the axis of greatest low-level convergence will
gradually shift eastward along the north-central Gulf Coast within
the discussion area through 18Z or so. With strong buoyancy and
moisture located near/just offshore, intense updrafts and
convective bands will continue to persist in the discussion area,
with highest rainfall rates (exceeding 3 inches per hour at times)
exceeding any flash flood guidance thresholds. Flash flooding is
most likely to occur beneath any heavier bands and/or training
convection that can materialize and persist in the discussion
area.

It is worth noting that additional heavy precipitation may develop
west of the dominant convective band near Mobile Bay through the
afternoon depending on redevelopment of low-level confluence axes
near/east of the cyclone center. This can foster repeating
convection over areas that received precipitation in western
portions of the discussion area.

Cook

ATTN...WFO...BMX...FFC...JAN...LIX...MOB...TAE...

ATTN...RFC...LMRFC...SERFC...NWC...

LAT...LON 32498667 32448540 32088505 31118503 30168518
29898534 30048559 30238612 30198703 30038784
30038868 30208903 31118936 31758940 32198916
32438819
$$
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AWUS01 KWNH 191721
FFGMPD
FLZ000-GAZ000-ALZ000-192318-

Mesoscale Precipitation Discussion 0355
NWS Weather Prediction Center College Park MD
120 PM EDT Sat Jun 19 2021

Areas affected...southeastern Alabama, Florida Panhandle, and
southwestern Georgia

Concerning...Heavy rainfall...Flash flooding likely

Valid 191718Z - 192318Z

Summary...Slow-moving convection on the southeastern periphery of
Tropical Cyclone Claudette will continue a risk of flash flooding
especially in the Florida Panhandle and vicinity through 00Z.

Discussion...Most of the heaviest convection on the southeastern
periphery of Claudette has been confined to one or two dominant
convective bands over the past 6 hours or so. The bands are
focused along a strongly confluent low-level wind field, which has
supported ascent within a very moist (2.2+ inches PW) and unstable
(2000+ J/kg MLCAPE) environment, allowing for areas of 2-3.5
inch-per-hour rainfall rates at times. The bands have produced
widespread areas of 2-5 inches of rain and isolated amounts as
high as 7.5. The highest amounts have so far been confined to
land areas nearer the stronger instability (located within 100 mi
of the coast and areas offshore).

These trends should continue through the evening hours.
HRRR/HREF/Nam and other guidance suggests that at least one or two
bands of convection should persist or gradually become more
elongated from southwest to northeast across the discussion area.
The localized training of convection will continue to allow for
widespread heavy rain to shift eastward, with many areas of 2-5
inch rainfall (and locally higher amounts) to occur across the
discussion area. The rainfall rates have overwhelmed flash flood
guidance (especially in flood-prone areas) and resulted in flash
flood impacts - especially in the Pensacola area recently.

Cook

ATTN...WFO...BMX...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32648425 32248332 31328294 30888307 30418348
30178409 29738512 29638587 30128700 30968719
31748690 32298635 32508549
$$
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AWUS01 KWNH 192023
FFGMPD
ILZ000-MOZ000-200112-

Mesoscale Precipitation Discussion 0356
NWS Weather Prediction Center College Park MD
423 PM EDT Sat Jun 19 2021

Areas affected...PORTIONS OF EASTERN MISSOURI AND WESTERN
ILLINOIS...INCLUDING THE ST LOUIS METRO AREA

Concerning...Heavy rainfall...Flash flooding possible

Valid 192012Z - 200112Z

Summary...A west-northwest to east-southeast area of back-building
convection along an axis of favored low-level frontogenesis will
result in an enhanced risk of flash flooding through 01Z.

Discussion...At 20Z, a surface cold front was draped across
northern Missouri and northwest Illinois. With the uptick in
pre-frontal south-southwesterly flow in the lower levels, the
airmass south of this front continues to destabilize this
afternoon as per satellite and radar trends, particularly across
portions of northeast and east-central Missouri where mixed-layer
CAPES average between 3000-4000 j/kg per the latest SPC
mesoanalysis. At the same time, the deep-layer moisture pooling is
also helping to raise PWAT values (1.6 to 1.8+ inches currently).

Albeit subtle, the position of the outlook area southwest of a
departing northern stream shortwave is resulting in weak
divergence aloft, with the focused area of deep-layer lift and
low-level frontogenesis aiding to the initiation of convective
clusters across portions of northeast and eastern Missouri into
western Illinois. As the afternoon progresses, the convection is
expected to grow upscale and expand across the outlook area,
particularly across portions of northeast and eastern Missouri
along the axis of greatest deep-layer instability. Given the
favorable thermodynamical environment, hourly rainfall rates of
2-2.5 inches are anticipated underneath the strongest cells, which
may lead to localized flash flooding, particularly in urban and
other areas prone to flash flooding. The latest CAM guidance
indicates pockets of 3-5" totals through 01Z over the outlook
area. Given the likely expansion of the convection upstream
(toward the axis of maximum instability), along with the
southeasterly storm motions, some cell training is expected,
thereby giving credence to these higher amounts indicated by the
CAMs.

Hurley

ATTN...WFO...ILX...LSX...PAH...

ATTN...RFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 39819149 39729003 39348896 38488894 38028992
38399102 38999196 39559205
$$
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AWUS01 KWNH 201001
FFGMPD
FLZ000-GAZ000-ALZ000-201500-

Mesoscale Precipitation Discussion 0364...Corrected
NWS Weather Prediction Center College Park MD
601 AM EDT Sun Jun 20 2021

Corrected for Changed Areas Affected

Areas affected...Florida Panhandle, Southeast AL, Southwest GA

Concerning...Heavy rainfall...Flash flooding possible

Valid 200951Z - 201500Z

Summary...Expanding coverage of thunderstorms in warm advection
ahead of an MCV will create an increasing flash flood risk this
morning. Multiple rounds of convection with rain rates to 2"/hr
are possible. Rainfall of 1-3" with isolated higher totals is
expected.

Discussion...A potent MCV stemming from a long-lasting forward
propagating MCS which has raced eastward overnight is now lifting
E/NE east of Hastings, NE. This MCV is being driven in part by a
robust and amplifying mid-level shortwave, and is moving into a
tropical airmass characterized by PWs around 1.5" and MUCape of
1500-2500 J/kg. A stationary front was analyzed draped west to
east along the MO/IA border, and recent VWPs indicate the 850mb
LLJ is increasing to 25-35 kts from the SW. This low-level SW flow
is isentropically ascending the stationary front, leading to
locally enhanced ascent across the region.

As the MCV continues to move eastward, ascent through PVA ahead of
the parent shortwave, isentropic upglide, low-level convergence
along the nose of the LLJ, and some enhanced acceleration east of
the MCV should maximize into the favorable thermodynamics. Recent
reflectivity from KEAX and KOAX indicate convection expanding
rapidly within the WAA regime and organizing due to bulk shear of
25-35 kts, with radar-estimated rainfall rates of 1-2"/hr becoming
common. While mean 850-300mb winds are robust to the E/NE at 20-30
kts, several rounds of heavy rainfall are possible during the next
few hours.

The HREF hourly rain probabilities suggest rainfall rates of 1-2"
will remain common through 12Z before beginning to wane as the MCS
moves into subtly drier air and the LLJ begins to veer, weakening
the ascent. During this time, rainfall of 1-3" is likely in many
locations as shown by the high-res guidance, and 6-hr HREF EAS
probabilities for 1" are above 60%, indicating both the agreement
of the members and the potential for excessive rainfall. While
recent rainfall has been modest during the past 14-days leading to
drier than normal soil moisture, there have been pockets of
rainfall 150% of normal during this time frame in SW IA. Here, FFG
is locally reduced to 1.5-2"/3hrs, and exceedance probabilities
are as high as 50%. Isolated flash flooding is possible through
early morning, but is most likely should this heavy rainfall occur
atop these locally more saturated soils.


Weiss

ATTN...WFO...BMX...FFC...JAX...MOB...TAE...

ATTN...RFC...SERFC...NWC...

LAT...LON 32888426 32808366 32508303 32078261 31648242
31058232 30588228 30238243 29958259 29708287
29528332 29428379 29448447 29498495 29668553
29878601 30138625 30498637 31068626 31558597
32118552 32568511 32778480
$$
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AWUS01 KWNH 201923
FFGMPD
NCZ000-SCZ000-210122-

Mesoscale Precipitation Discussion 0366
NWS Weather Prediction Center College Park MD
323 PM EDT Sun Jun 20 2021

Areas affected...portions of North and South Carolina

Concerning...Heavy rainfall...Flash flooding possible

Valid 201922Z - 210122Z

Summary...Gradually increasing convective coverage could result in
a few areas of flash flooding this afternoon and evening.

Discussion...Ahead of the eventual path of TD Claudette, strong
insolation amid a moist and increasingly buoyant airmass
(characterized by 2-2.3 inch PW values and around 2000 J/kg
MLCAPE) was fostering robust convective development recently. The
storms are in an environment with southwesterly flow aloft and
were moving northeastward at around 15-20 knots. However, the
weak low-level confluence and orientation of the development was
allowing for convection to repeat/develop in areas that have
received around 1-3 inches of rain earlier and have FFG values
ranging from 1-2 inch-per-hour thresholds. The very moist airmass
was allowing for rainfall rates to exceed these thresholds beneath
the heavier updrafts (up to around 2.5 inches per hour at times),
suggesting that at least a spotty flash flood threat should
materialize especially wherever training convection can occur.

Over time, convective coverage should continue to increase through
at least sunset due to continued insolation and low-level
convergence ahead of Claudette. There may be a downtick in
convective coverage thereafter due to loss of insolation, although
the moist environment should still sustain a few lingering storms
after sunset especially where updrafts can ingest non-convectively
modified air.

Cook

ATTN...WFO...AKQ...CAE...CHS...GSP...ILM...MHX...RAH...

ATTN...RFC...SERFC...NWC...

LAT...LON 36507687 35757645 35247670 34627730 33947811
33447893 32747988 32568062 32898137 33258164
34078207 34768161 35558024 36197842
$$
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AWUS01 KWNH 211917
FFGMPD
VAZ000-WVZ000-OHZ000-TNZ000-KYZ000-220116-

Mesoscale Precipitation Discussion 0371
NWS Weather Prediction Center College Park MD
316 PM EDT Mon Jun 21 2021

Areas affected...Central/Eastern Kentucky...Central Appalachians

Concerning...Heavy rainfall...Flash flooding possible

Valid 211916Z - 220116Z

Summary...Training thunderstorms along and ahead of a cold front
will be capable of producing hourly rain totals of 1-2" at times
and could lead to flash flooding across portions of the lower Ohio
Valley and central Appalachians through early evening.

Discussion...Large scale forcing for ascent provided by the
approach of a shortwave trough is focused over portions of the
lower Ohio Valley into the central Appalachians this afternoon. At
the surface, a seasonably strong cold front is analyzed generally
along/north of the Ohio River. The environment ahead of this
feature is very warm and moist, characterized by dewpoints in the
lower to middle 70s with a recently GPS analyzed PW of 1.6-1.8".
There is more than sufficient amounts of instability available
given both the surface heating and low/mid level lapse rates. The
latest SPC mesoanalysis showed MLCAPEs of 2000-2500 J/kg.

Current radar imagery shows an organizing line of thunderstorms
congealing just ahead of the cold front, maximized with the better
low level convergence. This activity is moving east/northeast and
is aligned fairly well with the mean flow, suggesting an increased
potential for training/backbuilding. Recent radar imagery also
shows potential for some 1.5 to near 2" hourly totals and this
aligns with the recent HREF probabilities which peak between
19-23Z for the greatest potential for reaching these intense rain
rates. Total amounts through 00Z could reach localized 3-4".

These storms will be moving across areas more susceptible to flash
flooding with low water spots and terrain and could lead to flash
flooding. 14-day rainfall departures for eastern KY and WV are
much above normal with higher than normal soil moisture
saturation. The HREF shows modest probabilities of exceeding the
12Z FFG, 20-40 percent, through the afternoon, particularly across
eastern KY into far western/southwest WV.

Taylor

ATTN...WFO...ILN...JKL...LMK...OHX...PAH...RLX...RNK...

ATTN...RFC...LMRFC...OHRFC...NWC...

LAT...LON 38928055 37878041 37138296 36688463 36188772
37298756 38098454 38598263
$$
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AWUS01 KWNH 282100
FFGMPD
MDZ000-VAZ000-WVZ000-290100-

Mesoscale Precipitation Discussion 0405
NWS Weather Prediction Center College Park MD
459 PM EDT Mon Jun 28 2021

Areas affected...West Virginia...Ext Western MD...

Concerning...Heavy rainfall...Flash flooding possible

Valid 282100Z - 290100Z

SUMMARY...Numerous pulse thunderstorms with rain rates and
sub-hourly totals of 1.5-2.5" pose possible isolated flash
flooding conditions.

DISCUSSION...Deeper moisture/instability across the Cumberland
Plateau is sloshed up into the higher terrain of the central WV
Appalachians with weak upslope and southwesterly flow pushing the
tight gradient in moisture into the area of concern. Deeper mean
layer flow is highly confluent across the 850-7H layer on the
western periphery of a sharp anticyclonic flow. Upslope flow from
the east as well, provided sufficient surface moisture convergence
to initiate a line of pulse to weakly organized convection. LPW
aslo denotes the main updraft core from 850-5H is about 1.1"
indicative of high moisture. Given modest flux convergence may
result in rates of 2-2.25"/hr. Given complex terrain, these
hourly totals have the potential to exceed 1 hour FFG values
particularly across central to northeast WV where the values are
less than 2". Outflow is likely to kick off additional cells
perhaps even cells eastward...and with mean deep layer flow
generally north-northwest to north-northeast, there may be some
repeat tracks that would further increase the potential to even
exceed 3hr FFG values which are generally below 2.5". Currently
threat is from Webster toward Randolph county but should expand
both northeast and southwest with time along with the overall
general propagation of the current cells toward the
north-northwest through the remainder of daylight hours before
remaining instability wanes.

Gallina

ATTN...WFO...LWX...PBZ...RLX...RNK...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 39667953 39577886 39147877 38617937 38048067
37478179 37958233 38918137 39548051
$$
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AWUS01 KWNH 282316
FFGMPD
ILZ000-MOZ000-290500-

Mesoscale Precipitation Discussion 0408
NWS Weather Prediction Center College Park MD
716 PM EDT Mon Jun 28 2021

Areas affected...Southwest to Central IL...

Concerning...Heavy rainfall...Flash flooding possible

Valid 282315Z - 290500Z

SUMMARY...Cycles of highly efficient but generally short-lived
thunderstorms traversing saturated ground conditions pose highly
scattered but likely flash flooding through early overnight hours.

DISCUSSION...Moisture streaming out of the western Gulf along the
western perimeter of deep sub-tropical high across the South surge
into proximity of the deep layer positive-tilt trof that has
dominated the Central U.S. for days. Ample deep moisture remains
pooled just southeast of the mean trof axis along/southeast of a
surface stationary front with near/over 2" total PWats extending
from southern Lake Michigan to southeast KS. While overall
thermal profiles continue to warm with lessening lapse rates day
by day, peak solar angle is sufficient to heat the surface
conditions to support SBCAPEs of 3000 J/kg within the warm sector.
Weak but sufficient 15-20kts of LLJ advect the unstable air into
proximity of weak mid to upper level impulses to support scattered
convective development across the same general axis.

Once again, an active cycle is blossoming across Central MO with
numerous cells breaking out with tops cooling below -60C.
However, winds are weak and each cell may only cycle with one or
two overshooting updrafts before weakening and becoming more
stratiform in nature. So peak rates of 2.5"/hr are common and may
be in close proximity to other cells, given deep layered
unidirectional steering flow, there are some occasional repeats
within a 2-3 hour period to support isolated 3-4" totals. The
real concern here is the axis of development remains stationary
over days so ground conditions are fully saturated with NASA SPoRT
LIS 0-40cm ratios generally over 90% from SE KS to NW IND...with
pockets of near 100% very common through that axis. As a result
FFG values are likely to be exceeded (less than 1.5"/hr and
2"/3hr) across much of MO into SW IL. There is greater distance
between instability and moisture axis across NE IL into IND, and
so many hi-res CAMs led by recent HRRRs suggest development to
remain in proximity to MO and SW IL through the evening and
overnight hours. ARW solutions have been poorer and FV3-LAM has
been worst performing through the afternoon to help in trying to
pinpoint any specific area/county within the area of concern.

Gallina

ATTN...WFO...DVN...EAX...ILX...LSX...SGF...

ATTN...RFC...ABRFC...LMRFC...MBRFC...NCRFC...NWC...

LAT...LON 40759026 40678900 39818865 39148941 38379055
37339246 37049333 37019418 37359456 38509435
39439316
$$
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AWUS01 KWNH 301750
FFGMPD
PAZ000-WVZ000-OHZ000-302249-

Mesoscale Precipitation Discussion 0418
NWS Weather Prediction Center College Park MD
149 PM EDT Wed Jun 30 2021

Areas affected...Southeast OH and Southwest PA

Concerning...Heavy rainfall...Flash flooding possible

Valid 301749Z - 302249Z

SUMMARY...Recent radar and satellite trends indicate the potential
for isolated flash flooding across portions of southeast OH, far
northern WV and southwestern PA through mid afternoon.

DISCUSSION...Latest surface observations and visible satellite are
detecting a southwest to northeast oriented convergence axis from
southeast OH into southwest PA. Convection has rapidly developed
along this axis over the past hour or two. Meanwhile we have also
been tracking an intense small convective cluster as it tracks
across southeast OH. The motion of this convective cluster should
take it along the aforementioned convergence axis....resulting in
a narrow axis of potential training over the next few hours.

The environment is characterized by MLCAPE over 2000 J/kg and PWs
around 1.75"...plenty sufficient for heavy rainfall rates. Latest
MRMS data indicates instantaneous rainfall rates of around 4" in
the heavier activity. Thus it would only take relatively brief
training to get rainfall amounts approaching 2" in under an hour.

Soil conditions over most of the MPD area are at well below normal
saturation levels. So this region is not in an overly susceptible
position for flash flooding. It will likely take some training to
result in any flooding...and even at that it will most likely stay
confined to any more susceptible low lying or urban areas.
Nonetheless the latest radar/satellite representation does suggest
a small scale training risk over this area over the next couple
hours resulting in the aforementioned localized flash flood risk.

Chenard

ATTN...WFO...CTP...PBZ...RLX...

ATTN...RFC...MARFC...OHRFC...NWC...

LAT...LON 41107881 40877845 40507878 40017973 39678050
39548139 40148167 40388150 40728060 40957974
$$
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