735
AWUS01 KWNH 071832
FFGMPD
VAZ000-NCZ000-SCZ000-GAZ000-TNZ000-080031-

Mesoscale Precipitation Discussion 0583
NWS Weather Prediction Center College Park MD
232 PM EDT Sun Jul 07 2024

Areas affected...Portions of the Mid-Atlantic...Southeast

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

Valid 071831Z - 080031Z

Summary...Slow moving thunderstorms are expanding in coverage and
intensity across portions of the Mid-Atlantic and Southeast ahead
of a weak cold front. Slow storm motions and 2-3"/hr rainfall
could lead to a few instances of flash flooding, particularly with
any localized training/repeating.

Discussion...Surface analysis highlights a weak wavy cold front,
and lee troughing across portions of the Mid-Atlantic and
Southeast. Along and ahead of the front, recent IR and radar
imagery depict expanding coverage and intensity of slow moving
thunderstorms with 5-10 kt storm motions estimated from RAX VWP.
Locally, a storm west of Raleigh with rapidly cooling cloud tops
briefly maintained 3"/hr rainfall rates per RAX earlier, leading
to elevated CREST Streamflows of 200-300 cfs/smi before weakening.

Unsurprisingly, the warm sector ahead of the front remains
supportive for periods of very heavy rainfall, as mesoanalysis
estimates show upwards of 3000 J/kg MUCAPE and 2.1-2.4" PWATS
entrenched across the region. Through the afternoon, weak
low-level convergence along the front will continue to drive slow
moving pulse thunderstorms with periods of 2-3"/hour rainfall
rates at times. Although the weak forcing and shear profiles will
ensure the heavy rainfall footprint is spotty in nature, the 12Z
HREF neighborhood probabilities show a high (45-60%) chance of 10
year ARI exceedences by 0Z tonight across the region, with some
signal (15-20%) of 100 year ARI exceedences noted. This suggests
locally very heavy rainfall (4-5") of rainfall is possible where
cells can locally train and repeat along the synoptic front,
future outflows, and the sea-breeze closer the coast. This could
lead to a few instances of flash flooding, with 1-3 HR FFGs of
2-4" noted across the region. Urban zones, and locations in
complex terrain along the Appalachians have a locally greater
chance of isolated flash flooding issues this afternoon.

Asherman

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

ATTN...WFO...AKQ...CAE...FFC...GSP...ILM...MHX...MRX...RAH...
RNK...

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

LAT...LON   36948153 36668046 36437882 36517755 36657631
            36007581 35117681 34848013 33908249 33918384
            34228465 35158440 35828368 36358264