Flash Flood Guidance
Issued by NWS
Issued by NWS
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506 AWUS01 KWNH 251851 FFGMPD NYZ000-PAZ000-MDZ000-VAZ000-WVZ000-OHZ000-260050- Mesoscale Precipitation Discussion 0322 NWS Weather Prediction Center College Park MD 250 PM EDT Sat May 25 2024 Areas affected...Far Southeast OH...Northern and Eastern WV...Far Northwest VA...Western MD...Central and Western PA...Southern NY Concerning...Heavy rainfall...Flash flooding possible Valid 251850Z - 260050Z SUMMARY...Increasing coverage of showers and thunderstorms is expected this afternoon and into this evening. Some relatively slow-moving cells will be capable of producing locally heavy rainfall and an isolated threat for flash flooding. DISCUSSION...Satellite and radar imagery already shows a broken axis of showers and thunderstorms gradually expanding in coverage across western PA and into southern NY. The activity is forming in a relatively moist and unstable airmass characterized by MLCAPE values that have risen to 1000 to 1500+ J/kg and with PWs locally as high as 1.2 to 1.4 inches. The greatest concentration of moisture and instability is currently pooled across eastern OH and western PA out ahead of an approaching cold front. A shortwave trough crossing through the Great Lakes region will be responsible for advancing this cold front gradually off to the east this afternoon and evening which coupled with the thermodynamic environment should favor an additional expansion of convection off to the east and south including areas from southern NY through central PA and also to the southwest across the MD/WV panhandles and adjacent areas of northern WV and southeast OH. The early to mid-afternoon visible satellite imagery shows an expanding field of moderate CU and some TCU across southeast OH and southwest PA and this is suggestive of convective initiation soon taking place as additional surface heating/solar insolation further destabilizes the boundary layer. Rainfall rates with the stronger storms are expected to reach 1.5+ inches/hour, and with some of the cells tending to be rather slow-moving and locally repeating over the same area, some spotty storm total amounts of 2 to 3+ inches will be possible. This coupled with relatively moist antecedent conditions suggest an isolated threat of flash flooding will be possible this afternoon and into the evening hours. The more urbanized locations will be most susceptible to runoff problems. Orrison ...Please see www.wpc.ncep.noaa.gov for graphic product... ATTN...WFO...BGM...BUF...CTP...LWX...PBZ...RLX... ATTN...RFC...MARFC...NERFC...OHRFC...NWC... LAT...LON 42977698 42927614 42667587 42077606 41437628 40187695 39387774 38877876 38748054 38978152 39418176 39938165 40528105 41068006 42387793