Flash Flood Guidance
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Issued by NWS
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620 AWUS01 KWNH 100010 FFGMPD PAZ000-MDZ000-WVZ000-OHZ000-100415- Mesoscale Precipitation Discussion 0253 NWS Weather Prediction Center College Park MD 809 PM EDT Thu May 09 2024 Areas affected...Northern WV...Far Western MD...ExtSouthwest PA...Ext Southeast OH... Concerning...Heavy rainfall...Flash flooding possible Valid 100008Z - 100415Z SUMMARY...Repeating thunderstorms and upslope moisture flux may support spots up to 2+" totals in 1-3hrs resulting in possible localized flash flooding. DISCUSSION...GOES-E WV depicts an elongated positive tilt trof across the Great Lakes with a lobe of shortwave energy crossign through west-central Ohio at this time. This has supported a few surface inflections along teh frontal boundary extending across S PA south of Wheeling, WV to the deeper low SE of ZZV, before extending further southwest to an inflection just east of Cincinnati. Deep layered flow has remained solidly eastward generally orthogonal to the central Appalachian terrain, though with the surface wave in proximity, pooled moisture and slightly backed flow has enhanced surface to boundary layer moisture convergence to the front across WV. Deep layer flow ahead of the surface wave provides an ideal narrow corridor for cell to train along with very slow southward propagation. Otherwise, stronger moisture flux converence into the terrain has sprouted a few isolated cells in advance. Good solar heating throughout the day supported modest unstable air with 1000 J/kg of MLCAPE still remaining and 1.25" of moisture (mostly in the lowest layers given upper 50s/lower 60s Tds. This should support solid moisture loading into the downdrafts for intense rainfall rates occasionally reaching 1", but may uptick as wind flow near the wave increases slightly to the upslope flow. As such spots of 1.5-2" may occur downstream of the surface wave. While not particularly robust, it is through complex terrain and may result in spotty incidents of flash flooding given FFG values well in the range for both 1 and 3hr time steps. Still, coverage and intensity does not rise to higher probability ans so is only considered possible through the early overnight period. Gallina ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...CTP...LWX...PBZ...RLX... ATTN...RFC...MARFC...OHRFC...NWC... LAT...LON 40067854 39807842 39297860 38907904 38677953 38628050 38818226 39328208 39838091 39977954