Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 12 2024 18:58:40 AWUS01 KWNH 121858 FFGMPD ALZ000-130055- Mesoscale Precipitation Discussion 0998 NWS Weather Prediction Center College Park MD 258 PM EDT Thu Sep 12 2024 Areas affected...central to northern AL Concerning...Heavy rainfall...Flash flooding likely Valid 121855Z - 130055Z SUMMARY...A relatively focused/narrow axis or multiple axes of heavy rain are expected to set up from central to northern AL through 01Z. Rainfall rates of 1 to 2 in/hr are expected early on, increasing potentially to about 3 in/hr on an isolated basis toward 00Z. Flash flooding is considered likely with rainfall totals potentially in the 3-5 inch range by 01Z. DISCUSSION...18Z surface observations placed T.D. Francine around 20 miles east of GWO tracking toward the north near 10 kt. Combining visible imagery with surface observations helped place a warm front which extended from eastern AL into western AL, southeastward into the FL Panhandle with mostly overcast skies to its northeast along with one or two bands of moderate to heavy rain. Broken cloud cover southwest of the warm front was allowing sufficient solar insolation to support a nose of MLCAPE between 500 and 1000 J/kg over southwestern AL via the 18Z SPC mesoanalysis. Low level convergence near the warm front in the 0 to 1 km AGL layer was fairly pronounced over west-central AL, with ESE winds between 40-50 kt at 925 over central AL and southwesterly winds of 20 kt in the warm sector at Mobile Bay (via area VAD wind plots). Meanwhile, precipitable water values were sampled across the region between 1.8 and 2.1 inches at 17Z via GPS data. The warm front is forecast to lift slowly northeastward through 00Z as continued daytime heating likely supports the advancement of 1000+ J/kg MLCAPE northward into portions of central AL. While some lowering magnitudes are expected as Francine continues to track north, low level convergent flow will continue to support 1 or more axes of heavy rain into the late afternoon and early evening over central to northern AL, oriented NNW to SSE, similar to the mean steering flow which will allow for periods of training. The environment supports rainfall rates of 1-2 in/hr, but increasing instability through the afternoon and the approach of left-exit region divergence within a 70-80 kt upper level jet max forecast to strengthen and advance eastward from the lower Sabine River Valley 00Z should help to increase rainfall intensity. Increased forcing for ascent may allow training to support rainfall rates near 3 in/hr by early evening. Localized totals of 3 to 5 inches may occur through 01Z, potentially overlapping with urban centers, including the Birmingham metropolitan region. While not expected to be widespread across central to northern AL, a couple areas of flash flooding will be likely. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!4fc5RrvpJY1Pj-Rsb_NL4RmSGIw4PkkDwSgE0L66pX5Gs9jJQF334tIOxJkoHpXQrp3s= vHtuK6k9veqiFKy1HgX8Gis$ for graphic product... ATTN...WFO...BMX...HUN...MOB... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 34858765 34358654 33558619 32458610 32048655=20 32008735 32608779 34268797=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) .