Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jul 25 2023 21:00:25 AWUS01 KWNH 252100 FFGMPD CTZ000-NYZ000-NJZ000-PAZ000-DEZ000-MDZ000-VAZ000-DCZ000-260200- Mesoscale Precipitation Discussion 0794 NWS Weather Prediction Center College Park MD 459 PM EDT Tue Jul 25 2023 Areas affected...Eastern portions of the Mid-Atlantic States Concerning...Heavy rainfall...Flash flooding possible Valid 252059Z - 260200Z Summary...Areas of showers and thunderstorms will continue to develop and lift northeast through this evening. Rainfall rates of 1-2"/hr are likely within deeper convection, resulting in locally an additional 1-3" of rain. Flash flooding is possible. Discussion...The regional radar mosaic this aftn shows multiple areas of thunderstorms moving slowly eastward across the Mid-Atlantic. The most intense convection is occurring near the coast of NJ, DE, and the eastern shore of MD where instability is still plentiful noted by SPC RAP analyzed MUCAPE of 1500-2000 J/kg overlapped with PWs of 1.5-1.7 inches. This is still downstream of prior convection, so the atmosphere remains primed for thunderstorms. Forcing across this area remains intense as well within the RRQ of a departing jet streak and downstream of a potent shortwave/vorticity maxima over PA. Together these features are producing impressive deep layer ascent while concurrently drawing additional moisture northward. This is resulting in Corfidi vectors that are weakening while remaining aligned to the mean 0-6km wind, suggesting increased potential for backbuilding/training of cells with 2"/hr rainfall rates the next few hours. Within this area, HREF probabilities for more than 3" are as high as 25%, with most of this falling in just 1-2 hours. This suggests a continued flash flood risk into the evening. Upstream of this area, a secondary axis of convection may develop as suggested by several of the high-res members. The regional satellite imagery shows a line of clouds developing south of the potent vorticity max over PA, and this could be the onset of renewed convection. MUCAPE and PWs remain elevated in this area as the environment has mostly been missed by thunderstorms so far today. While confidence is low as to how much additional development will occur, storms that do develop could have rainfall rates of more than 2"/hr, and 15-min rainfall accumulations as high as 0.5-0.75 inches as forecast by the HRRR. These storms could train along the confluence boundary south of the shortwave as it moves east, and where training occurs 1-3" of rainfall is possible. This rain may occur atop soils that are saturated from 1-3" of rainfall earlier today, and over lower FFG in urban areas. Although confidence is modest, any training that does occur, especially near I-95 from Washington, D.C. to Philadelphia, could result in instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!65QKzI2h5QlfWtx9Z5TVnuOiWfTQH788e3SJ6KV-l1jqDLaV6bum9f7xgehVEAQdksSd= i3jYXalWbdps7DccntoURHw$ for graphic product... ATTN...WFO...AKQ...CTP...LWX...OKX...PHI... ATTN...RFC...MARFC...NERFC...NWC... LAT...LON 41297377 41277321 41197264 41007243 40577281=20 40177347 39947369 39407417 38947440 38637455=20 38107489 37747538 37547625 37637660 37937692=20 38317731 38437740 38777755 39147740 39887635=20 40397534 40837464=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 3.14-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .