Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Aug 03 2023 15:00:35 AWUS01 KWNH 031500 FFGMPD GAZ000-TNZ000-KYZ000-ALZ000-ILZ000-MOZ000-ARZ000-031800- Mesoscale Precipitation Discussion 0847 NWS Weather Prediction Center College Park MD 1100 AM EDT Thu Aug 03 2023 Areas affected...Ozarks through the Tennessee Valley Concerning...Heavy rainfall...Flash flooding possible Valid 031459Z - 031800Z Summary...An MCS dropping southeast out of Missouri will slowly wane through the afternoon. Rainfall rates of 2"/hr should begin to weaken, but continued training could result in 2-3" of rain with locally higher amounts. Flash flooding is possible. Discussion...The regional radar mosaic this morning shows an impressive MCS shifting southeast within mid-level NW flow around a ridge of high pressure to the south. This MCS has shown some signs of weakening in response to the veering LLJ noted in regional VWPs, but is maintaining intensity beyond most of the available high-res. Despite the slow weakening/veering of the LLJ, forcing is still impressive downstream of a convectively enhanced shortwave and potent MCV noted in the radar imagery. Southwest of this MCV, a convergence boundary has developed which is aiding in low-level ascent on the nose of the 30kt LLJ. This LLJ is helping to advect robust thermodynamics eastward with PWs above 1.8 inches collocated with MUCAPE of 3000+ J/Kg. Within this overlap of forcing and impressive moisture/instability, estimated rain rates from KPAH have been above 2"/hr resulting in ongoing flash flooding. Confidence during the next few hours is less than usual due to struggles of the high-res models. However, the veering of the LLJ still advecting intense thermodynamics into the system, a potent MCV, and at least modest downstream thickness diffluence suggests this MCS will persist for a few more hours before finally waning. The HREF indicates that rain intensity will gradually ease noted by reducing probabilities of 1"/hr and 2"/hr rates, but even as they weaken, training should allow for rapid accumulations of more than 0.5"/15 min as reflected by the HRRR. Additionally, upwind propagation vectors will likely veer more to the SW and collapse in response to the shifting LLJ, suggesting a continued backbuilding/training threat along the convergence boundary and into the higher instability. Where the most impressive training can occur, 2-3" of rain with locally higher amounts is possible as shown by HREF probabilities for 3" reaching 20-30%. Parts of MO/IL/KY and western TN have been saturated recently noted by AHPS 14-day rainfall that in some areas is more than 200% of normal and USGS streamflow anomalies around the 90th percentile. This excludes overnight rainfall which has been measured by MRMS to be as much as 2-5" in some areas, so some areas are even more sensitive. Despite the slow reduction of intensity expected, training atop these sensitive soils or into any urban areas could still result in instances of flash flooding through the early aftn. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7jr_j5C3RD-xD8Wl4-4m7R8lU22E01kDi5tKBrJvE7SJ9K6ZdgmnFeqt8oe2IKA6pgNh= -JYP2_pZwD7wTk_AxYoIPZI$ for graphic product... ATTN...WFO...FFC...HUN...LMK...LSX...MEG...MRX...OHX...PAH... ATTN...RFC...LMRFC...NCRFC...OHRFC...NWC... LAT...LON 37849004 37778880 37418628 36888524 36198491=20 35408505 34928549 34788620 34958781 35558910=20 36259012 37269093 37709105=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) .