AWUS01 KWNH 011810
FFGMPD
SCZ000-FLZ000-GAZ000-020000-

Mesoscale Precipitation Discussion 0533
NWS Weather Prediction Center College Park MD
210 PM EDT Mon Jul 01 2024

Areas affected...Coastal Georgia and South Carolina...

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

Valid 011810Z - 020000Z

SUMMARY...Very deep moisture and slow thunderstorms along the
coast to produce 2.5"/hr, spots of 3-5", and possible rapid
inundation flooding through the evening.

DISCUSSION...18z surface analysis depicts a slowly sagging cold
front across the NC/SC border connecting to a weak surface
wave/inverted trough across West-central GA just west of Macon.
South of the boundary, very high theta-E air with mid to upper 70s
Tds and temperatures starting to near the mid to upper 80s, spots
of 90+F. Total moisture through depth ranges from 2.1 to 2.5" and
SBCAPEs of 2500-3500 J/kg from CHS into S GA. Deep warm layer
between 14-15Kft and given parameters will allow for efficient
rainfall production/tropical showers capable of 2.5"+/hr.

Aloft, GOES-E WV shows the split in upper-level flow in the col
along the eastern edge of the large scale ridge across the central
Gulf states. This is weakening mid-level steering flow to allow
for very slow cell motions and propagation vectors to near zero at
or along the GA/SC coastline. Yet, effective bulk shear given
directional shear should support some minor organization to
convective cells allowing for increased duration for multiple
up/down convective cycles before forward propagation would occur.
As such, a weak low to mid-level circulation is spinning up in
across S central GA, leading to streamline convergence across SE
GA as well.

Frictional convergence and onshore flow/moisture flux may further
lock convection to coastal regions to support increased rainfall
duration. As such, spots of 3-5" are becoming more likely
particularly further north along the central SC coast (proximity
to the front) and northeast GA. This is supported by recent HRRR
solutions as well as 17z WoFS; with 50th percentile around 3.5"
and 90th percentile over 6". As such, there is increasing
confidence of 3-5" totals along the coast which may result in
spots of possible rapid inundation flooding.

Gallina

ATTN...WFO...CHS...ILM...JAX...

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

LAT...LON 33607902 33407895 32937934 31878086 30918145
30668251 31058264 31818204 32678138 33078076
33268021 33507975 33587949
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AWUS01 KWNH 071008
FFGMPD
SCZ000-GAZ000-071530-

Mesoscale Precipitation Discussion 1135
NWS Weather Prediction Center College Park MD
508 AM EST Thu Nov 07 2024

Areas affected...Southeast GA...Southern SC...

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

Valid 071010Z - 071530Z

SUMMARY...Flooding likely to continue though potential for intense
rain-rates capable of inducing flash flooding reducing with time
and overall coverage.

DISCUSSION...A large area of 4-10" rainfall extends across eastern
GA into southwest to south-central SC with slow expansion toward
the coastal Plain over the past few hours. Large scale ascent
pattern remains fairly strong with upper-level divergence pattern
along right entrance of broad polar jet across the Carolinas.
However, the area is shifting east-northeast and reducing
slightly. Still, this is maintaining a solid dual fetch of
low-level flow from the northeast Gulf as well as off the Gulf
stream parallel to the NE FL/GA coast. Cold pool from the heavy
rainfall continues to allow for a moderately steep isentropic
boundary across the area from SE GA into the Low Country, with a
very slow east-southeast drift due to the responding low level
inflow from the south-southeast. VWP denotes continued 20-25kts
of SE flow nearly orthogonally intersecting the boundary and
northeasterly flow across central SC. CIRA LPW and RAP analysis
denote deep profile of highly anomalous moisture with values of
2.25" through depth with sfc-850mb over from .9" to 1.15" across
the area of concern; so dynamics and moisture continue to be in
place to maintain rainfall efficiency.

However, unstable air mass continues to diminish in areal coverage
and intensity as the profile becomes more staturated and warms
aloft; restricting itself to the Gulf Stream and coastal GA where
low level flow has been generally divergent before starting to
accelerate into SE SC where convergence is maximized. Values of
500-1000 J/kg remain but only along the upstream edge of the
complex along the Savannah River Valley. As such, limited
overall convection capable of rates over 1.5-2"/hr are expected
over the diurnal minimum in activity of early morning/daybreak,
mainly near/southeast of mid-level exiting shortwave seen near
Wilkenson county, GA or at the 700-850mb low feature seen in RADAR
in Montgomery county. Smaller localized spots of 2-4" totals
remain possible to induce new incidents of flash flooding though
the 15z period.

Moderate downstream blow-off shield precipitation within the more
gentle isentropic ascent pattern will maintain moderate rainfall
rates across the flooded areas from Emanuel to Orangeburg with
counties with occasional hourly rates exceeding .5". This will
likely help to maintain the expanding riverine flooding as pluvial
flooding continues to channel into localized creeks/streams. An
additional 2-3" remains possible through the morning hours given
favorable upstream redevelopment and training as the upper-level
forcing moves northeast.

As such, flooding will remain likely across the area of concern,
though incidents of flash flooding are considered possible given
reducing coverage/intensity required to exceed FFG where heavier
rain did not fall last evening/overnight across coastal E GA/S Low
Country of SC.

Gallina

ATTN...WFO...CAE...CHS...FFC...ILM...

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

LAT...LON 34118019 33907956 33397924 32977945 32757980
32578007 32208058 31698098 31418123 31528156
31888193 32048228 31938282 32008307 32298309
32688271 33158214 33478172 33678137 34038071


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