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AWUS01 KWNH 072351
FFGMPD
NCZ000-SCZ000-GAZ000-080530-

Mesoscale Precipitation Discussion 0585
NWS Weather Prediction Center College Park MD
751 PM EDT Sun Jul 07 2024

Areas affected...Western South Carolina and Eastern Georgia

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

Valid 072350Z - 080530Z

SUMMARY...Storms colliding in an atmosphere with abundant moisture
and instability are likely to cause flash flooding, especially in
areas hard hit by storms yesterday. Locally significant flash
flooding possible.

DISCUSSION...Flash flooding is likely this evening across South
Carolina and Georgia as 2 areas of storms...one moving north over
south Georgia, and the other moving southeast over northwest South
Carolina collide somewhere near the I-20 corridor. This area was
hard hit with storms just yesterday, so many areas, especially in
and around Augusta have yet to recover from the heavy rainfall
last evening. Thus...FFGs are lower in these hard-hit areas.
Further, the storms are in an environment highly favorable for
efficient warm-rain processes. PWATs are between 2.3 and 2.5
inches based on SPC Mesoanalysis, and CAPE values are between
2,000 and 3,000 J/kg. These variables will help support the storms
producing heavy rainfall. Rates with the storms over northwestern
South Carolina have locally approached 3 inches per hour.

The collision of the 2 areas of storms and their respective
outflow boundaries will further enhance the lift by increasing the
forcing in this area. Given inflow of additional moisture from the
Atlantic, this will not only support long-lived heavy rain
producing storms, but also further enhance the rates the strongest
storms may achieve. Thus, rates to 4 inches per hour are possible
with the strongest storms this evening. 18Z HREF neighborhood
probability guidance shows a corridor of 70-80% chance of
exceeding 3 inches of rain in 6 hours along the I-20 corridor from
Augusta through Columbia, a 50-60% chance of exceeding 10-year
ARIs in 6 hours, and a 50-60% chance of exceeding 3-hour FFGs
between 00Z and 03Z.

CAMs guidance over the next few hours shows the storms moving SE
largely overtaking the ones moving N as they follow the
instability southeastward towards the coast...but with some
potential slowing of their forward speed as the outflow boundaries
between the 2 sets of storms collide.

Wegman

...Please see www.wpc.ncep.noaa.gov for graphic product...

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

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

LAT...LON   34908095 34627981 33578014 32618104 32398211
            32748348 34088339 34168247 34888144