Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jun 18 2025 16:58:38 AWUS01 KWNH 181657 FFGMPD NYZ000-NJZ000-PAZ000-MDZ000-VAZ000-DCZ000-WVZ000-182256- Mesoscale Precipitation Discussion 0477 NWS Weather Prediction Center College Park MD 1256 PM EDT Wed Jun 18 2025 Areas affected...Eastern OH Valley...Northern Mid Atlantic...Interior Northeast Concerning...Heavy rainfall...Flash flooding possible Valid 181656Z - 182256Z Summary...Shallow thunderstorms are gradually expanding in coverage and intensity across the Eastern OH Valley, Northern Mid-Atlantic, and Interior Northeast. Periods of repeating cells containing 1.5 to locally 2"/hr rainfall rates could support additional isolated flash flooding this afternoon in light of recent heavy rainfall in the region. Discussion...Day Cloud Phase RGB and LightningCast data suggest shallow thunderstorms across the Eastern OH Valley, Northern Mid-Atlantic, and Interior Northeast are intensifying as an extremely moist airmass destabilizes beneath eroding low-level clouds. The most persistent cells were initially roughly along I-80 in Western PA, which prompted several Flash Flood Warnings as they repeated over an area impacted yesterday and realized 1.5-1.8"/hr rainfall rates per KCCX. Additional flooding was also noted near Buffalo, NY as an axis of cells stalled and trained overhead. As highlighted in the 12Z soundings from PIT and IAD, the airmass across the region remains very supportive for efficient warm rain production in these cells, with saturated profiles containing 1.7-2.1" PWATs, 1000-2000 J/KG of MUCAPE, and warm cloud layers of 13,000-14,000 feet noted. Sufficient shear remains as well to support at least loosely organized multicellular storm modes, with 20-35 kts depicted in recent mesoanalysis. Over the next several hours, a general trend of expanding multicells is expected as a weak shortwave over Western OH approaches from the west amid continued surface heating. Westerly steering flow should permit for periods of repeating cells, although storm coverage should remain more scattered compared to yesterday's event. As instability builds and additional cells form, both the HREF and REFS neighborhood probabilities show an increasing likelihood of at least 1"/hr rates and 1-3 HR FFG exceedance beginning around the 17-18z time frame. With FFGs in the region as low as .25-1.5", additional isolated flash flooding is possible as these cells expand and periodically repeat. Asherman=20=20 ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!6uRcE_EgBXsLRi5pJ0sbzuWgV4XEYN7K2asNVaGFLKdKlAqkR5vEYo0cyJ488jl06vw3= a70HyzBBPh5lllBNkrsXG7o$ for graphic product... ATTN...WFO...BGM...BUF...CLE...CTP...LWX...PBZ...PHI... ATTN...RFC...RHA...TAR...TIR...NWC... LAT...LON 42617863 42507757 41357647 40507484 39587600=20 38627691 38617789 39237850 39597895 40118005=20 40778037 41508026 42247970=20 =3D =3D =3D To unsubscribe from WX-STORM and you already have a login, go to https://lists.illinois.edu and use the "Unsubscribe" link. Otherwise email Chris Novy at cnovy@cox.net and ask to be removed from WX-STORM. --- SBBSecho 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .