Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Sep 13 2024 17:54:24 AWUS01 KWNH 131754 FFGMPD TNZ000-ALZ000-MSZ000-132350- Mesoscale Precipitation Discussion 1002 NWS Weather Prediction Center College Park MD 153 PM EDT Fri Sep 13 2024 Areas affected...central/northern AL into southern TN Concerning...Heavy rainfall...Flash flooding possible Valid 131753Z - 132350Z SUMMARY...Narrow training axes of heavy rain will support a localized flash flood threat across central to northern AL into far southern TN through 00Z. Rainfall rates of 1-2 in/hr are expected. DISCUSSION...17Z regional radar imagery showed a broken/narrow axis of showers/thunderstorms extending from southern TN into western AL, located along an elevated convergence axis, out ahead of a cold front associated with Post-Tropical Cyclone Francine. The convergence axis has been slowly moving east over the past few hours but rainfall intensity has been increasing following trends in instability. The 17Z SPC mesoanalysis indicated MLCAPE of 500 to 1500+ (locally) extending from Middle TN into much of AL with little to no CIN. However, visible imagery showed stratus/overcast conditions across eastern to northeastern AL where low level convective inhibition is likely to keep convection at bay in the short term. The 12Z BMX sounding and recent GPS data across AL showed precipitable water values of 1.3 to 1.7 inches (...and higher across far southeastern AL), but with a notable dry layer aloft, extending as far down as just below 700 mb. Continued daytime heating, especially where current breaks in cloud cover exist, will support a continued expansion of instability across central to northern AL with greater coverage of 1500+ J/kg anticipated by 21Z. Mean southerly steering flow will allow for training of heavy rain at times along the roughly north-south oriented convergence axis slowly moving east and other smaller scale axes of convergence to the east of the existing line over western AL. While a pronounced layer of dry air noted in the mid-upper levels may deter broader coverage of heavy rainfall development, at least localized areas of training with 1-2 in/hr rain rates will be possible. These rates may overlap with recent pockets of heavy rain which fell across the region over the past 48 hours and/or sensitive urban areas to produce possible, but likely remaining localized, areas of flash flooding through 00Z. Otto ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!_nmhOjId5iEf5LJTU_Dwru07mAtt6uFxUGUjRjtt3P15EukVwrWuS5AFsjVA-PRrbM3-= eVyjZZiwQibu4BvZQ77LbhY$ for graphic product... ATTN...WFO...BMX...HUN...MEG...MOB...OHX... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 35748802 35688766 35318702 33948656 32418612=20 31818693 31758758 32048800 33418787 34628818=20 35288837 35568829=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) .