-
MESO: Heavy Rain/Flooding
From
Mike Powell@618:250/1 to
All on Tue Apr 16 09:25:00 2024
AWUS01 KWNH 161421
FFGMPD
MOZ000-MNZ000-IAZ000-KSZ000-NEZ000-SDZ000-161800-
Mesoscale Precipitation Discussion 0158
NWS Weather Prediction Center College Park MD
1021 AM EDT Tue Apr 16 2024
Areas affected...eastern Nebraska, southeastern South Dakota,
northeastern Kansas, northwestern Missouri, and western into
central Iowa
Concerning...Heavy rainfall...Flash flooding possible
Valid 161420Z - 161800Z
Summary...Bands of convection are resulting in prolonged rain
rates (including 2+ inch/hr rates at times) across the discussion
area. Areas/spots of flash flooding are possible through 18Z this
morning.
Discussion...Over the last hour or so, a couple of dominant
convective bands have taken on a favorable orientation for
training despite relatively fast steering flow and storm motions.
One of these bands extended from near Yankton, SD to near
Columbus, NE, with rightward-moving structured embedded and
assisting in both 1 inch/hr rain rates and 2-2.5 inch/3-hr rain
rates beneath the band. This area was continuing to ingest
surface-based parcels due to southeasterly low-level flow and near
60F dewpoints beneath very cold air aloft (-20C at 500mb),
contributing to relatively efficient rain rates. Local FFGs in
the 1.5 inch/hr range were being approached on a localized basis,
suggesting a continued flash flood risk as long as convection
remains rooted near the surface. Some cells were moving northward
toward cooler surface air, however, which may weaken storms and
lower rain rates as they drift into southeastern South Dakota.
Southeast of this area, a second band of more robust convection
extended from near Clarinda in southwest Iowa through Topeka, KS.
These cells are also training and fostering areas of nearly 2
inch/hr rain rates due to favorable orientation to south-southwest
steering flow aloft. Stronger buoyancy in this area was also
contributing to slightly stronger/deeper updrafts per satellite
imagery. These storms were also lifting northward toward a
low-level boundary and stable air across central Iowa, although
ascent/forcing aloft may sustain training cells toward the Des
Moines, IA area after 16Z or so.
Models suggest that warm advection/destabilization will develop
northward into areas of central/northwestern Iowa over time,
resulting in a broader spatial opportunity for deep, training
updrafts and heavy rain rates. Areas of 1-2 inch/hr rain rates
are expected to approach FFG thresholds over the discussion area
on at least a spotty basis through 18Z or so. The threat could
persist beyond 18Z, although model trends seem to indicate a
faster forward progression of convection (and less training)
through the afternoon hours. This scenario will be re-evaluated
for another potential MPD after 18Z.
Cook
ATTN...WFO...DMX...EAX...FSD...ICT...MPX...OAX...SGF...TOP...
ATTN...RFC...ABRFC...MBRFC...NCRFC...NWC...
LAT...LON 44399753 44339634 43329360 41849265 39539264
38389370 38069443 38039543 39329568 40479675
42379784 43669793
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From
Mike Powell@618:250/1 to
All on Thu Apr 25 18:44:00 2024
AWUS01 KWNH 252235
FFGMPD
KSZ000-NEZ000-COZ000-260345-
Mesoscale Precipitation Discussion 0172
NWS Weather Prediction Center College Park MD
634 PM EDT Thu Apr 25 2024
Areas affected...Northwest Kansas...Southwest Nebraska...Northeast
Colorado...
Concerning...Heavy rainfall...Flash flooding possible
Valid 252235Z - 260345Z
SUMMARY...Increasing moisture flux convergence into convective
clusters within potentially favorable flow regime for
back-building and training rotating cells pose possible localize
flash flooding concerns particularly after 00z this evening.
DISCUSSION...22z surface analysis depicts rapidly deepening
surface low in east-central CO with well defined dry line and warm
fronts extending from a triple point near the Colorado/Kansas
border at the Cheyenne/Sherman county line. The dry line is wavy
extending southward along the state line though appears to be
short-term retreating into southeast Colorado which may provide a
pivotal development region for later training/repeating as they
move northward toward the triple point. The effective warm sector
is represented by low to mid 80s Temps over lower 60s Tds.
Strong/steep lapse rates via a strong EML above the boundary layer
suggest higher than normal evaporatimve effects especially in the
early stages of development. However, the very moist low levels
are strongly convergent while also being reinforced along the
north side of the warm front by cooler but still mid to upper 50s
Tds that may entrain into elevated updrafts that meander north of
the frontal zone. Compound this with strong rotating updrafts
will support localized isallobaric inflow/moisture flux loading
the lower updraft profile with ample moisture to develop heavy
rainfall accompanying hail generation.
GOES-E WV suite also depicts favorable left exit jet ascent for
cell evacuation and potential for cells to grow upscale into
clusters and perhaps a small complex. Cell motions within the
cluster are expected to have a northeast motion at 30-40kts but
stronger rotation, should slow to 20kts per RAP Bunker propagation
vectors. Additionally, with the approach of shortwave ridging,
backing cell motions toward a more northerly component will
support the potential for repeating/training profiles particularly
after 00z as mid-level drying reduces from earlier evaporation
into the environment. As such, cells producing 1-1.5"/hr rates
may start to encroach into the 1.5-2"/hr rates. This presents the
increasing possibility of pockets/scattered clusters of 2-3"
totals in 2-3 hour period. While the grounds have been dry,
natural FFG values would be in reach of being exceeded in
localized spots given 1hr values of 1.5-2" and 2-2.5/3hrs. So
while severe threat is currently the primary hazard, the
hydrological risk will be steady increasing through 00z and even a
very strong slow moving high influx super-cell may induce
localized flash flooding in the short-term.
Gallina
ATTN...WFO...BOU...DDC...GID...GLD...LBF...
ATTN...RFC...ABRFC...MBRFC...NWC...
LAT...LON 41159979 40979916 40289894 38930043 38480142
39010188 39510237 39990323 40730306 41020220
41080090
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From
Mike Powell@618:250/1 to
All on Fri Apr 26 08:04:00 2024
AWUS01 KWNH 261023
FFGMPD
MOZ000-ARZ000-TXZ000-OKZ000-KSZ000-261530-
Mesoscale Precipitation Discussion 0175
NWS Weather Prediction Center College Park MD
622 AM EDT Fri Apr 26 2024
Areas affected...Portions of Far Northern TX...South-Central to
Northeast OK...Far Southeast KS...Far Northwest AR...Southwest MO
Concerning...Heavy rainfall...Flash flooding possible
Valid 261020Z - 261530Z
SUMMARY...Heavy showers and thunderstorms with some instances of
cell-training may result in areas of flash flooding this morning.
DISCUSSION...Radar and satellite imagery shows a broken QLCS
advancing generally east-northeast across portions of the Red
River Valley, with somewhat more disorganized activity noted
farther up to the northeast across northeast OK and southeast KS.
A shortwave trough continues to cross the region while interacting
with a moderately unstable airmass characterized by MUCAPE values
of 2000 to 2500+ J/kg, and with a persistently moist
south-southwest low-level jet of 40 to 50 kts. Given the level of
forcing and instability that is in place, the convective activity
should persist through the morning hours and may even locally
expand in coverage.
Some cell-training will be possible as the convection evolves
close to the Red River Valley and up through eastern OK over the
next few hours. Rainfall rates are expected to reach as high as
1.5 to 2 inches/hour given the level of moisture transport and
instability focusing across the region. The latest HRRR guidance
has been trending wetter and strongly supports the idea of the
convection becoming oriented more parallel to the deeper layer
southwest steering flow. The HRRR does favor some potential for
localized 3 to 5 inch rainfall totals across eastern OK going
through late this morning given the cell-training concerns. This
may result in some instances of flash flooding as a result across
this region.
The other concern this morning is also farther northeast up across
far southeast KS and into southwest MO where heavy rainfall over
the last 24 hours has led to notably moist soil conditions and
elevated streamflows at least locally. Some additional broken
clusters of convection are expected here with the arrival of the
aforementioned shortwave energy, with an additional 2 to 3 inches
of rain possible by late morning. Some instances of flash flooding
will be possible here as a result.
Orrison
ATTN...WFO...EAX...FWD...ICT...LZK...OUN...SGF...SHV...TSA...
ATTN...RFC...ABRFC...LMRFC...MBRFC...WGRFC...NWC...
LAT...LON 38479407 38079297 36629322 35049410 33859524
33159699 33219861 33599872 34259776 35109704
35949631 36519582 37299536 38119463
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From
Mike Powell@618:250/1 to
All on Sun May 5 08:35:00 2024
AWUS01 KWNH 051226
FFGMPD
MOZ000-ARZ000-OKZ000-KSZ000-051800-
Mesoscale Precipitation Discussion 0227...Corrected
NWS Weather Prediction Center College Park MD
825 AM EDT Sun May 05 2024
Corrected for Corrected Discussion
Areas affected...Northeast Oklahoma through Central Arkansas
Concerning...Heavy rainfall...Flash flooding likely
Valid 051156Z - 051800Z
SUMMARY...Flash flooding likely as storms developing out ahead of
an advancing MCS moving across eastern Oklahoma and southern
Arkansas move into the hydrologically sensitive Ozarks.
DISCUSSION...Storms that have developed across Oklahoma and
eastern Arkansas have been producing localized rainfall rates of
up to 2 inches per hour. Instability is between 500 and 1,000 J/kg
of MUCAPE based on SPC Mesoanalysis, and PWATs are around 1.75
inches. The abundant moisture and decent instability will support
additional thunderstorm development through midday across
northeast Oklahoma and much of Arkansas.
The leading edge of the MCS, as well as any pre-MCS convection
will lift northward with time. The MCS is wrapping around a center
point near southeast Oklahoma in response to a northward moving
shortwave in the upper levels. This will keep convection ongoing
and slow-moving to nearly stationary across northeast Oklahoma and
northwest Arkansas. Meanwhile, storms developing on the south and
east side of the line will move faster to the north, which would
decrease flash flooding potential...except those storms will have
a greater tap of moisture and instability, which will allow them
to grow stronger than the convection to their west.
Soils across much of the area are nearly saturated. Heavier
convection will have the potential to produce rates to 2.5 inches
per hour, however even in areas that don't see the heavier
convection, steady rainfall through the morning falling on nearly
saturated soils will result in most of the rainfall converting to
runoff. This will result in widely scattered instances of flash
flooding, with the potential in both hydrologically sensitive
areas of terrain and urban areas for isolated instances of significant/considerable flash flooding.
Wegman
ATTN...WFO...ICT...LZK...SGF...SHV...TSA...
ATTN...RFC...ABRFC...LMRFC...NWC...
LAT...LON 37169592 37049493 36819374 36549306 36399223
35939152 34919135 34319178 33839227 33229275
33229322 33639393 34949495 36109606 36559633
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From
Mike Powell@618:250/1 to
All on Mon May 6 13:22:00 2024
AWUS01 KWNH 061800
FFGMPD
MTZ000-WYZ000-062300-
Mesoscale Precipitation Discussion 0230...Corrected
NWS Weather Prediction Center College Park MD
159 PM EDT Mon May 06 2024
Areas affected...Portions of Eastern Montana and Northeastern
Wyoming
Concerning...Heavy rainfall...Flash flooding possible
Valid 061659Z - 062300Z
SUMMARY... The comma-head region of a deepening cyclone will
feature steady rainfall with embedded thunderstorms capable of
producing flash flooding.
DISCUSSION...Low-level moisture inflow into portions of the upper
High Plains is advecting an air mass with dew points into the 50s
into this typically dry part of the country. This is being driven
by a developing strong low-pressure system threatening to break
monthly low pressure records in the western Dakotas. The moisture
feed into the storm originates in the Gulf, and is advecting into
the area on up to 50 kt winds in the lower levels. Meanwhile, as
is typical with mature storms, dry air aloft making up the comma
is ending the precipitation further east into the western Dakotas.
The dry air aloft is enhancing potential instability, which has
allowed for a few thunderstorms to develop on the
dry-slot/comma-head interface. These storms have caused greater
than an inch per hour rainfall rates, which have already caused
some localized flash flooding.
CAMs guidance suggests additional thunderstorm development is
likely, as noted by the line extending north of the Black Hills.
The storms are most likely to form along the eastern edge of the
precipitation shield, or as the current line shows, extending as a
band of storms into the dry slot. Should the storms move over
flood sensitive areas, additional flash flooding is possible.
Wegman
ATTN...WFO...BYZ...GGW...RIW...UNR...
ATTN...RFC...MBRFC...NWC...
LAT...LON 48340694 48170640 48050624 47650605 46740561
45920545 44590520 44280563 44190675 44250714
44730778 45910816 46410823 46950826 47430803
48110748
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From
Mike Powell@618:250/1 to
All on Mon May 6 17:51:00 2024
AWUS01 KWNH 062122
FFGMPD
VAZ000-NCZ000-TNZ000-KYZ000-070300-
Mesoscale Precipitation Discussion 0232...Corrected
NWS Weather Prediction Center College Park MD
522 PM EDT Mon May 06 2024
Corrected for typo in last paragraph
Areas affected...central/eastern KY/TN into the Appalachians
Concerning...Heavy rainfall...Flash flooding possible
Valid 062117Z - 070300Z
SUMMARY...Periods of training could allow for a quick 2-3 inches
of rain across portions of southern KY into TN and the adjacent
Appalachians through ~03Z. Localized flash flooding may result
with 1-2 in/hr rates.
DISCUSSION...Visible imagery at 2045Z showed the presence of an
low level low (centered 925-850 mb) along the eastern IN/KY
border, tracking toward the east. A smaller mesoscale circulation
was noted to the south, over south-central KY. South of the
925-850 mb low were active thunderstorms, most of which were along
an elevated convergence axis noted on visible imagery, extending
west to east through central TN before curving toward the
northeast into south-central KY. The environment over southern KY
into TN was represented by 1000 to 2500 J/kg MLCAPE and near 1.5
inches via the 20Z SPC mesoanalysis.
Average cell motions were toward the east at 20-25 kt over TN, but
concern has increased for the potential for cells to repeat or
train from west to east through the evening. As the 925-850 mb low
tracks toward the east into the early overnight hours, ongoing
storms along the convergence axis are expected to generally track
into eastern KY/TN and the Appalachians, posing a localized threat
for flash flooding due to repeating west to east motions. A
continued influx of moist and unstable air from the south may
support additional convective development along the rain-cooled
outflow with similar potential for west to east repeating and
training later this evening...which could support 1-2 in/hr
rainfall rates and localized 2-3 inch totals in ~2 hours or less
time. Area flash flood guidance is generally 1.5 to 2.5 inches in
3 hours for the region, some exceedance and localized flash
flooding may result through roughly 03Z .
Otto
ATTN...WFO...GSP...HUN...JKL...LMK...MEG...MRX...OHX...
ATTN...RFC...LMRFC...OHRFC...SERFC...NWC...
LAT...LON 36978440 36958300 36888241 36798197 36578189
36178209 35968238 35708279 35508311 35258385
35048520 35158791 36128806 36678694 36938528
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