Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Jul 22 2024 16:48:55 AWUS01 KWNH 221648 FFGMPD NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-222247- Mesoscale Precipitation Discussion 0692 NWS Weather Prediction Center College Park MD 1248 PM EDT Mon Jul 22 2024 Areas affected...central/eastern Maryland, Washington DC, Delaware, and southern/central Pennsylvania Concerning...Heavy rainfall...Flash flooding possible Valid 221647Z - 222247Z Summary...Isolated flash flood potential is becoming apparent across the discussion area, with the greatest risk across urban areas of Washington/Baltimore and Wilmington, DE through 22Z. Discussion...Over the past half hour, radar mosaic imagery has depicted a general increase in convective activity near the Chesapeake Bay, These cells were drifting slowly northward/northwestward toward the Washington/Baltimore corridor. Additional cells were located over central Pennsylvania near Harrisburg. These cells were in a moist, destabilizing environment characterized by 1.7-2 inch PW values and SBCAPE values approaching 2000 J/kg. The cells were also likely being influenced by both 1) weak/subtle surface convergence just west of the Chesapeake Bay and 2) weak ascent associated with subtle mid-level shortwave troughs over Virginia. Wind fields aloft are weak (generally below 30 knots from the low to mid-levels), which are allowing slow-moving cells to produce spots of rain rates approaching 1 inch/hr per MRMS. Antecedent conditions across the region are relatively dry, with FFGs peaking at around 3 inches/hr outside of more densely populated areas, and around 1-1.5 inches/hr across urban areas. These factors suggest an isolated, primarily urbanized flash flood threat in the short term. Over time, additional development of showers and a few thunderstorms will continue to produce areas of 1-2 inch/hr rain rates - especially as 1) the airmass across the region continues to destabilize and 2) spots of repeating/training become more likely over time. Additional thunderstorm activity across higher terrain of western Pennsylvania/West Virginia could also pose a flash flood risk as it migrates eastward toward areas of higher moisture content across the discussion area. Isolated flash flood potential is expected to continue through most of the afternoon. Cook ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8gMkT0c6yhnJ0zwN0-8EoShevgvSsClsWsZPu2S_fYVQmtwnlvFjGxrRcWQiaru2H61h= hDPYSJiah2uU-C6jni9O_Yo$ for graphic product... ATTN...WFO...AKQ...BGM...CTP...LWX...PHI... ATTN...RFC...MARFC...NWC... LAT...LON 41407641 41077539 40397519 39167514 38297529=20 37897621 38107693 39437760 40817787 41327733=20 =20=20=20=20=20=20=20=20=20=20=20=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) .