Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 31 2024 12:23:00 AWUS01 KWNH 311222 FFGMPD VAZ000-NCZ000-OHZ000-GAZ000-TNZ000-KYZ000-INZ000-311730- Mesoscale Precipitation Discussion 0764 NWS Weather Prediction Center College Park MD 822 AM EDT Wed Jul 31 2024 Areas affected...eastern Kentcuky, eastern Tennessee Concerning...Heavy rainfall...Flash flooding possible Valid 311221Z - 311730Z Summary...Showers and thunderstorms developing ahead of a vorticity maxima will expand into eastern KY and TN this morning. Rainfall rates of 1-2"/hr are likely, which may produce spots of 1-3" of rainfall leading to instances of flash flooding. Discussion...The regional radar mosaic this morning depicts a rapid expansion of convective activity from far southern Ohio southward through Kentucky and into northern Tennessee. This convection is blossoming immediately downstream of a compact but potent vorticity maxima analyzed by the RAP and noted in the GOES-E WV imagery embedded within the broad NW flow. The accompanying PVA and subtle height falls are combining with weak LFQ diffluence to produce locally enhanced ascent. This lift is impinging into impressive thermodynamics as W/NW 850mb flow surges MUCAPE of 1000-2000 J/kg eastward to combine with PWs of 1.5 to 1.8 inches to produce an environment favorable for heavy rain rates. The guidance is struggling to resolve any of the ongoing activity, and it appears the high-res CAMs are generally missing the accompanying vorticity impulse responsible for this convection. The ARW and ARW2 are really the only two that suggest this morning activity should be occurring, so the evolution the next few hours is significantly dependent on an ingredients based approach and these two outputs. As bulk shear increases to 25-35 kts in the presence of the mid-level impulse, and the more robust thermodynamics get advected eastward, this should result in an expansion of convection with some organization into clusters through the late morning. Despite the lack of model agreement, the HREF neighborhood probabilities suggest rainfall rates have a 20-40% chance of exceeding 1"/hr, supported by the elevated CAPE and PWs. Although mean 0-6km winds are progressive at 15-20 kts, aligned propagation vectors to the long-axis of the developing convection could result in at least short-term training from NW to SE, resulting in corridors of 1-3" of rainfall. This region has been extremely wet recently with 7-day AHPS rainfall anomalies reaching 150-300% of normal in southern KY and much of eastern TN. This has caused a lowering of 3-hr FFG to less than 1.5" in many places, for which the HREF forecasts a 20-25% chance of exceedance despite a lack of model agreement. Additionally, MRMS 24-hr rainfall has been 2-4", which resulted in some instances of flash flooding yesterday. While flash flooding is not expected to be widespread, any heavy rain rates falling atop urban areas or sensitive soils could cause impacts. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!8VCfEBUZEh8XqRipiSpTxJqZYxRMcJo9kil67GHlc5rnAcJroYYJgmi84ELQWY_UXwWT= Paa8ETEULxWv1D6elRebG44$ for graphic product... ATTN...WFO...FFC...GSP...ILN...JKL...LMK...MRX...OHX...RLX... ATTN...RFC...LMRFC...OHRFC...SERFC...NWC... LAT...LON 39378478 38968373 37848276 36888248 36058253=20 35548268 34988353 34838420 34898480 35558561=20 37088602 38528558=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) .