Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Aug 29 2023 16:16:03 AWUS01 KWNH 291615 FFGMPD MDZ000-VAZ000-WVZ000-TNZ000-KYZ000-292200- Mesoscale Precipitation Discussion 1003 NWS Weather Prediction Center College Park MD 1215 PM EDT Tue Aug 29 2023 Areas affected...West Virginia...Southwest & Western VA...Eastern KY...Northeast TN...Ext Western MD... Concerning...Heavy rainfall...Flash flooding likely Valid 291615Z - 292200Z SUMMARY...Scattered thunderstorms with potentially intense sub-hourly rates (1"+/15 minutes) across recently saturated grounds and complex terrain pose localized flash flooding concerns through afternoon hours. DISCUSSION...GOES-E WV suite denotes decayed MCV, lingering mid-level shortwave lifting northeast along/just east of the spine of the Appalachians across NE TN into SW VA into the broader large scale trof over the Great Lakes. Given the placement, low to mid-level moisture stream has not been fully removed from west of the ridge line with a solid deformation/convergence axis across E KY into central WV. Moisture remains elevated with total PWATs around 1.75" even at the highest elevations of the mountain range, with Tds in the upper 60s to lower 70s across the area of concern. A few cells have developed along the axis, due to the stronger localized convergence, but insolation has been limited for broad scale increase in instability. However, GOES-E visible shows this trend is changing with broad erosion of the even the higher cirrus deck from E KY into northeast WV. Local soundings suggest limited capping in this moist adiabatic profiles, so any heating will rapidly increase MLCAPE with expected values of 1000-1500 J/kg by 17-18z.=20 The weak backed low to mid-level flow along/ahead of the wave should be the catalyst toward stronger organized convection but cells should quickly become intense with ample moisture flux to support 2"/hr rates, though sub-hourly totals are likely to be in 1"/15 minute range. Hi-Res CAMs suggest 18-19z development, but may trigger even an hour or so earlier, eventually with HREF peak signal of 1"/hr and 2"/hr in the 21-22z period reaching 75% and 25% respectively, especially further downstream into E WV, but some hints across Northeast TN at lower probability. Deep layer, mostly unidirectional steering flow toward the northeast may allow for some repeat incidents increasing potential for localized 2-3" totals. If there is one positive, propagation vectors aided by local cold pools suggest slow eastward shift likely to limit extreme totals to localized anchoring/storm scale effects. Recent above average rainfall has saturated the grounds and induced localized flash flooding over the past few days. Similar today, especially with even lower FFG values in the region suggest spots of flash flooding are likely especially after 20z. Gallina ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7eJEcbhqXWHs4bzuxz9kyoS3vm42mg-KZYgHK6BVTsTOvLRkYRn2WzTjwuEnfAFpnMGc= QaXaNW4g_dCdYuQwu3qgae8$ for graphic product... ATTN...WFO...JKL...LWX...MRX...PBZ...RLX...RNK... ATTN...RFC...LMRFC...MARFC...OHRFC...NWC... LAT...LON 39657931 39457830 38717846 37508028 36958144=20 36398302 36148442 36988458 37778344 38378240=20 38768182 39358079=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) .