Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Aug 04 2023 13:00:23 AWUS01 KWNH 041300 FFGMPD TNZ000-KYZ000-ALZ000-ILZ000-MSZ000-MOZ000-ARZ000-041730- Mesoscale Precipitation Discussion 0857...Corrected NWS Weather Prediction Center College Park MD 859 AM EDT Fri Aug 04 2023 Corrected for correted typo in third paragraph Areas affected...Ozarks into the Tennessee Valley Concerning...Heavy rainfall...Flash flooding likely Valid 041230Z - 041730Z Summary...Continued training of showers and thunderstorms through the morning will likely lead to instances of flash flooding. Rain rates of 1-2+"/hr are likely, which could result in 2-4" of rain with locally higher amounts. Where this rain occurs atop the most vulnerable soils, locally significant flash flooding is possible. Discussion...The regional radar mosaic this morning shows an impressive MCS aligned NW to SE from southeast MO through central AL. The convection embedded within this MCS is being forced by a 20-30 kt W/SW LLJ noted in regional VWPs, lifting isentropically atop a warm front analyzed by WPC, and converging efficiently into the convection where 850mb moisture transport vectors collapse. The LLJ is transporting PWs measured by GPS within the pre-convective environment of 1.75-2 inches, resulting in moisture flux nearing +3 sigma according to the SREF. Additionally, MUCAPE analyzed by the SPC RAP is above 2000 J/kg, providing extremely favorable thermodynamics for heavy rainfall. This MCS has already resulted in MRMS measured QPE of 2-5+", with a few mesonet observations of over 7 inches in western KY. The LLJ will begin to veer and gradually weaken in the next few hours, but remain favorably oriented to persist heavy rain producing convection. Additionally, an MCV noted in the reflectivity and a convectively enhanced shortwave dropping out of MO will provide locally enhanced ascent. This should result in continued rain rates of 1-2"/hr as reflected by HREF probabilities, with short-term rainfall possibly reaching 0.75" (brief 3+"/hr rates) as noted on the sub-hourly HRRR. Storm motions, using the 0-6km mean wind as proxy, will remain NW to SE at 15 kts, which is parallel to the front suggesting training, and as the LLJ veers, subsequent Corfidi vector response will be to back more to the W/SW, suggesting an enhanced backbuilding threat as storms regenerate into the greater instability surging on the WAA. This setup will likely result in some areas receiving 2-4" of rain, with isolated amounts exceeding that as show by modest HREF probabilities for 5+" through 18Z. This are has seen multiple rounds of heavy rain during the last 14 days, which has resulted in USGS streamflow anomalies that are well above normal, and in some places at record values. This has compromised FFG considerably, and the HREF exceedance probabilities for 3-hr FFG reach as high as 45%. Instances of flash flooding are likely anywhere within this MCS, but where the most pronounced training occurs, locally significant impacts are possible. Weiss ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!7j-RpcbM-iHXPf-TTqkRLFtZY2Vij3Oo_tMWuF_Cw9F0zSJtNWAteEyRbyYWqxjrYYb1= D78kaOSAy8wBkfb-xiu8Qnk$ for graphic product... ATTN...WFO...BMX...HUN...JAN...LSX...LZK...MEG...OHX...PAH... SGF... ATTN...RFC...LMRFC...MBRFC...NCRFC...OHRFC...SERFC...NWC... LAT...LON 38059156 37939002 37518908 37338886 36588792=20 35348705 34138655 33628648 33238711 33448804=20 34328935 35439066 36129218 36649327 37669343=20 =20=20=20=20=20=20=20=20=20=20=20=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) .