Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jul 20 2023 09:46:34 AWUS01 KWNH 200946 FFGMPD NCZ000-TNZ000-KYZ000-201545- Mesoscale Precipitation Discussion 0768 NWS Weather Prediction Center College Park MD 545 AM EDT Thu Jul 20 2023 Areas affected...Southern KY...Middle and Eastern TN Concerning...Heavy rainfall...Flash flooding likely Valid 200945Z - 201545Z SUMMARY...Locally heavy showers and thunderstorms are expected to develop and expand in coverage over the next few hours. Some cell-training is expected, and this coupled with very heavy rainfall rates will likely produce some areas of flash flooding going through the morning hours. DISCUSSION...The latest GOES-16 IR/WV satellite imagery suggests some low-amplitude shortwave energy shearing east-southeast across the Lower OH Valley early this morning within the stronger deeper layer flow aloft. This energy coupled with the nose of a west-southwest low-level jet in the 850/925 mb layer of 30 to 40+ kts and interaction with a nearby weak stationary front should promote the development and gradual expansion of heavy showers and thunderstorms over the next few hours. Facilitating the convective threat going through the morning hours will be the transport a very moist and unstable airmass from upstream over the Middle MS Valley with PWs that are on the order of 1.75 to 2.0 inches, and MLCAPE values over central/southern MO of as much as 3000 to 4000 J/kg. The low-level jet will likely tend to veer a bit through the early to mid-morning hours which will allow it to become more parallel to the 850/300 mb layer flow. This will result in a favorable environment for at least some training bands of heavy showers and thunderstorms. Most of the 00Z HREF guidance have struggled all night with the details of how convection would initiate and evolve early this morning, and even the last several runs of the HRRR guidance have been inconsistent with the overall threat going through the morning time frame. However, radar imagery is showing convection beginning to initiate over of far southern KY and northern TN. This coupled with the overall environment suggests that there should be at least an uptick in convective organization and concerns for at least some localized swaths of heavy rainfall going through the morning hours. The MPD threat area is closely aligned with the new 06Z HREF EAS neighborhood probabilities for exceeding 1 inch of rain in a 6-hour period. Rainfall rates with these swaths of convection this morning should be quite intense and capable of reaching 2 to 3 inches/hour with the stronger cells. Given the cell-training concerns, some localized totals of 3 to 5 inches will be possible by late-morning. This will likely result in some areas of flash flooding. Orrison ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!9bF1FXmtKJGAxvLS6rVD6WID_6dwbV6wdBMqmPxl_fe4NQ6F-sV6Bvo5FruRZdzscWw_= T7YUPGIwz81Dkw-Kh99H8qI$ for graphic product... ATTN...WFO...GSP...JKL...LMK...MRX...OHX...PAH... ATTN...RFC...LMRFC...OHRFC...NWC... LAT...LON 37318739 37308602 36788439 36078340 35228375=20 35168532 35588659 36288767 36898788=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) .