Weather Prediction Center issues Mesoscale Precipitation Discussion #765 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE216
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Mesoscale Precipitation Discussion 0765
NWS Weather Prediction Center College Park MD
1103 AM EDT Sat Jul 18 2026
Areas affected...Southern & Central Appalachians
Concerning...Heavy rainfall...Flash flooding possible
Valid 181502Z - 182102Z
Summary...Showers and thunderstorms are beginning to develop due
to daytime heating. Hourly rain amounts to 2.5" are possible,
which could lead to flash flooding.
Discussion...CIN is eroding due to daytime heating under mostly
sunny skies. The region is within a confluence zone at 850 hPa
and ahead of a digging shortwave across the Great Lakes (which is
enhancing upper level difluence). Precipitable water values are
1.5-2". ML CAPE is 1000-2000 J/kg, and rising. Effective bulk
shear is 25-30 kts from northwest WV northward. The three hour
flash flood guidance is modest to low.
ML CAPE should rise another 500-1000 J/kg by late afternoon, which
should allow for convective expansion across the region. Given
the available ingredients, hourly rain amounts to 3" are possible
where cells merge, train, manage to backbuild, or move little
across the terrain or in the vicinity of a nearby front/thermal
gradient across western PA. Given the three hourly flash flood
guidance values and topographic relief across the region, this
degree of heavy rainfall would be highly problematic. Flash
flooding issues are expected to be widely scattered.
Roth
...Please see www.wpc.ncep.noaa.gov for graphic product...
ATTN...WFO...CLE...CTP...FFC...GSP...ILN...JKL...LWX...MRX...
PBZ...RLX...RNK...
ATTN...RFC...ALR...ORN...RHA...TIR...NWC...
LAT...LON 41637889 41077845 40357806 39597732 38187867
35948123 34458332 34508441 35308485 37388356
38538267 39668238 40328135 40908098 41568011
Source:
Weather Prediction Center issues Mesoscale Precipitation Discussion #765 concerning HEAVY RAINFALL...FLASH FLOODING POSSIBLE---------------
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