Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Aug 26 2023 19:17:03 AWUS01 KWNH 261916 FFGMPD TNZ000-KYZ000-INZ000-ILZ000-MOZ000-ARZ000-270115- Mesoscale Precipitation Discussion 0985 NWS Weather Prediction Center College Park MD 316 PM EDT Sat Aug 26 2023 Areas affected...MO into IL and Lower OH Valley Concerning...Heavy rainfall...Flash flooding likely Valid 261915Z - 270115Z SUMMARY...A few areas of flash flooding appear likely across MO, IL and the Lower OH Valley through 01Z. Some rainfall rates could be as high as 2-3 in/hr with localized rainfall totals over 3 inches likely for a few spots, but coverage of these higher totals should remain somewhat localized. DISCUSSION...1830Z visible satellite imagery showed a broad swirl over northwestern MO, associated with an MCV that was tracking toward the ESE. Regional radar imagery helped identify several areas of thunderstorms over MO and IL, with some of the strongest cores along an outflow boundary extending from the Lower OH River into southeastern MO, and to the north in central IL, near a cold front. Cloud cover and earlier precipitation has resulted in reduced instability/increased convective inhibition for portions of central MO into southwestern IL, but surrounding areas to the south (MO Bootheel and central IL) showed 1000 to 2000+ J/kg MLCAPE on the 18Z SPC mesoanalysis. In terms of moisture...GPS, Blended TWP Imagery and SPC mesoanalysis data indicated precipitable water values within a tenth or two of 2 inches for the entire region, supportive of intense rainfall given the available instability. There are a few areas with elevated potential for heavy rain/flash flooding. First, near the outflow boundary, thunderstorms are likely to continue expanding within the unstable environment. Upstream development over central MO is expected after 21Z as the MCV tracks toward the southeast with low level inhibition being overcome through additional daytime heating and forcing ahead of the approaching vorticity max. The multiple rounds of storms may be enough to cause localized flash flooding despite a progressive movement to individual cells. Farther north, earlier clearing on visible satellite imagery ahead of a southward sagging cold front in IL is expected to support some slower moving thunderstorms from central IL into northern MO, where RAP guidance shows a relative minimum in deeper-layer steering flow, with 850-300 mb mean winds near 10 kt. Given the slower storm motions and similarly oriented 850 mb wind vectors, some short term training could support locally high rainfall rates in these areas. While coverage of flash flooding is not expected to be widespread across the MPD threat area, the environment is supportive of a few areas of flash flooding with rainfall rates between 2-3 in/hr with some of the stronger thunderstorm cores and localized totals in excess of 3 inches through 01Z. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-97VlQIAHFG7M16dBsXuUf2-3jgbP8fvWSWTUSXJfrQ518mmXAawUhl-EPPQjFYbo_wN= arIpDJPPdPLqi2HVS18jZE8$ for graphic product... ATTN...WFO...DVN...EAX...ILX...IND...LSX...LZK...MEG...OHX... PAH...SGF... ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...NWC... LAT...LON 40329021 40258984 40078881 39698814 39098770=20 38158728 37288751 36548809 36078917 35939091=20 36149220 36769293 37529342 38539366 38829363=20 39599303 40179189=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) .