Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Sep 29 2024 17:44:25 AWUS01 KWNH 291744 FFGMPD MDZ000-VAZ000-NCZ000-WVZ000-OHZ000-TNZ000-KYZ000-292300- Mesoscale Precipitation Discussion 1081 NWS Weather Prediction Center College Park MD 143 PM EDT Sun Sep 29 2024 Areas affected...Central Appalachians Concerning...Heavy rainfall...Flash flooding possible Valid 291743Z - 292300Z Summary...Clusters of showers and thunderstorms will develop and lift northward through the afternoon. Rainfall rates of 1-2"/hr within these cells could repeat to produce 1-3" of rainfall. This occurring atop pre-saturated soils may result in instances of flash flooding. Discussion...The regional radar mosaic this afternoon shows widespread light showers across the Ohio Valley and Mid-Atlantic, with embedded convective elements beginning to blossom across VA/WV. This convective activity is deepening in response to a ribbon of 500-1000 J/kg of SBCAPE which has expanded across the area south of a wedge front and north of a stationary front. PWs of 1.5-1.7 inches, or above the 90th percentile according to the SPC sounding climatology, are contributing to intensifying thermodynamics to support this convective activity. Forcing for ascent is additionally intensifying downstream of an upper low over KY, with SE 850mb winds of 10-15 kts lifting isentropically and orographically to combine with upper divergence and diffluence. As the aftn progresses, the high-res CAMs are in good agreement that convective coverage will expand in response to the increasing ascent within the favorable thermodynamics. Although coverage will likely remain scattered, aligned Corfidi vectors and mean 0-6km winds suggests repeating rounds of convection are likely in many areas. These thunderstorms will likely intensify through the aftn as well to produce rainfall rates for which both the HREF and REFS neighborhood probabilities indicate have a 40-50% of exceeding 1"/hr, and 15-min HRRR fields indicate an isolated potential for 2"/hr rates. Despite the progressive and scattered nature of these cells, multiple rounds lifting N/NW into the area could produce rainfall amounts of 1-3" in some areas. This region has been saturated recently, noted by 7-day rainfall departures from AHPS that area in most areas 300-600% of normal. This has led to fully saturated soils and compromised FFG that is as low as 0.75-1.5" in 3 hours. The HREF FFG exceedance probabilities peak as high as 70% by this evening, highest in the vicinity of Shenandoah NP and into the Allegheny Mountains. However, flash flooding will be possible anywhere the most intense rates repeat atop the saturated soils or across vulnerable terrain. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!5tyMelmmVF7n88FDockXczyN7XEko1ADrfkvKXVVWSxA1IUbf-vVuPhKDK20snOiGBUR= 9tFNj56tN_Y3DUjIjjnURn8$ for graphic product... ATTN...WFO...AKQ...ILN...JKL...LWX...MRX...PBZ...RLX...RNK... ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...NWC... LAT...LON 39688000 39577916 39057841 38017819 36697888=20 36398001 36428122 36648186 37068204 37588244=20 37798310 38078343 38628344 39078263 39468140=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) .