Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Wed Jul 31 2024 18:46:31 AWUS01 KWNH 311846 FFGMPD VAZ000-NCZ000-OHZ000-TNZ000-KYZ000-INZ000-ILZ000-010030- Mesoscale Precipitation Discussion 0770 NWS Weather Prediction Center College Park MD 245 PM EDT Wed Jul 31 2024 Areas affected...southern Indiana, central Kentucky, eastern Tennessee Concerning...Heavy rainfall...Flash flooding likely Valid 311844Z - 010030Z Summary...Showers and thunderstorms will increase ahead of a shortwave and train to the southeast into this evening. Rainfall rates of at least 2"/hr are likely at times, resulting in additional rainfall of 2-3" with locally higher amounts. Flash flooding is likely. Discussion...The GOES-E visible satellite imagery this afternoon shows rapidly deepening Cu/TCu aligned NW to SE from far southeast IN into southeast KY. This is reflective of deepening convection ahead of a residual convective MCV noted in radar and satellite dropping into southern IN, and the regional radar mosaic shows a rapid expanse in reflectivity showing that these updrafts are rapidly transitioning into showers and thunderstorms. The environment downstream of the MCV is quite impressive and favorable for thunderstorms, with PWs of 1.7-2.0 inches collocated with MLCAPE as high as 3000 J/kg. There exists a tight instability gradient from SW to NE as well, suggesting that convection will dive along this boundary to the southeast as it organizes into multicells or another MCS in response to 30-35 kts of bulk shear. Rainfall rates so far have been somewhat limited to less than 1"/hr in current activity, but this is more a response to just being in the early stages of development rather than being within a limited environment. The HREF neighborhood probabilities suggest a 15-20% chance for 2"/hr rates this evening, while the HRRR 15-min rainfall product indicates brief 3-4"/hr rates are possible. A recent polar orbiter pass and NUCAPS sounding over central KY indicates an impressive pre-MCS environment with PWs around 1.7 inches and freezing levels of 14,000 ft with modest mid-level lapse rates to support efficient warm-rain processes, so these rainfall rate predictions seem reasonable. Mean 850-300mb winds are forecast to be progressive at 15-25 kts to the southeast, but aligned and collapsed Corfidi vectors suggest cells will likely regenerate and train, at least until the MCS organizes and sweeps through to the southeast. Areas that receive an overlap of slow moving pre-MCS storms, and the MCS, could see 2-3" of rain with locally higher amounts as shown by HREF 3"/6hr neighborhood probabilities of 15-25%. Most concerning about this setup is that these heavy rain rates, even from individual cells, will be falling atop pre-conditioned soils. MRMS 24-hr rainfall has been as high as 4 inches (highest in southern KY and northeast TN), with 7-day rainfall from AHPS generally 150-300% of normal. This has compromised FFG across most of this area, with sensitive terrain features also increasing the potential for rapid runoff. Any cells moving through this area, especially where they occur multiple times to repeat heavy bouts of rainfall, will likely result in instances of flash flooding. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!84C-8txXyZTnut81cPU8qwYm_ekB96DQ4ZzEWiEeJMhg0ilW0z9wM_tnYoc_VHlJAIXq= oeeflnCTYSLem7m7xNIr1kg$ for graphic product... ATTN...WFO...GSP...ILN...ILX...IND...JKL...LMK...MRX...OHX... PAH... ATTN...RFC...LMRFC...OHRFC...NWC... LAT...LON 39738720 39648611 39238495 38678428 37478362=20 36478331 35728335 35278376 35268447 35518544=20 35948582 36708592 37278633 38268770 38628820=20 39028809 39338781=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) .