Subj : MESO: Nws Weather Prediction Center College Park Md To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Jan 09 2024 09:58:45 AWUS01 KWNH 090957 FFGMPD NCZ000-SCZ000-FLZ000-GAZ000-TNZ000-ALZ000-091600- Mesoscale Precipitation Discussion 0005 NWS Weather Prediction Center College Park MD 454 AM EST Tue Jan 09 2024 Areas affected...portions of southeast and east-central AL...west-central and northern GA...western SC/NC...far East TN Concerning...Heavy rainfall...Flash flooding likely Valid 091000Z - 091600Z Summary...Numerous instances of flash flooding are likely across portions of southern AL (along with the threat of locally significant flash flooding) where 1-3"/hr rainfall rates will continue (with additional short-term totals of 2-4"). Elsewhere, localized flash flooding is considered to be possible with rainfall rates mostly capped at 1"/hr (but still accumulating to the 2-4" range). Discussion...An MCC (mesoscale convective complex) continues to propagate eastward across southern AL and the western FL Panhandle early this morning. The strongest convection (and coldest cloud tops via GOES IR imagery) are located just to the east of the attendant low pressure system and cold front, effectively propagating eastward along the gradually northeastward advancing warm front. Repeating of 1-2"/hr rainfall rates has occurred most efficiently along the warm front, as semi-discrete convective cells are overtaken by a more dominant eastward moving squall line. This has resulted in localized streaks of 3-6" over the past 6 or so hours, gradually coming to an end in southern MS. Meanwhile, southern AL will continue to see some of the heaviest rainfall over the next several hours in association with the leading convection and approaching squall line, likely resulting in additional accumulations of 2-4". This overlaps already saturated terrain with corresponding flash flood guidance of 1-3", and additional numerous instances of flash flooding are most likely across this region (with relatively good agreement amongst the hi-res models, including the experimental WoFS, and well supported by the observational trends). Locally significant flash flooding also remains a threat where these 2-4" totals overlap with prior totals of 2-5". Farther northeast into west-central and northern GA and surrounding portions of SC, NC, and TN, rainfall rates are more likely to be capped at around 1"/hr due to the absence of instability. Instead, rainfall will largely be more stratiform resulting largely from mid and upper-level forcing (as well as from jet stream transportation of the hydrometeors from the primary MCC farther south). This may still result in some 3-hr totals exceeding 2" or 6-hr totals exceeding 3" (per HREF 40-km neighborhood probabilities ranging from 20-50%), but this is relatively close to the corresponding flash flood guidance (and antecedent conditions are relatively dry, per NASA SPoRT-LIS 0-1m soil moisture around the 2nd or 3rd decile). Perhaps the most at risk localities in this region are within the terrain surrounding the GA/SC/NC border region, where upslope flow from the incredibly strong low-level jet should contribute to the greatest chance of locally exceeding 3" through 16z. Overall, flash flooding is considered possible across this region through mid-morning, but this may change by mid-day and early afternoon with continued repeated ~1"/hr rates in the vicinity of western SC/NC. Churchill ....Please see https://urldefense.com/v3/__http://www.wpc.ncep.noaa.gov__;!!= DZ3fjg!-pNEyKW3gl98I4bLP7a0jdLXGZBHc8HGaTIu8OmlqUcL6E7kboa2LjssIjTv2TgI2GaP= LUQLqbvj4LischgYuL8N3UA$ for graphic product... ATTN...WFO...BMX...CAE...FFC...GSP...HUN...MOB...MRX...TAE... ATTN...RFC...LMRFC...SERFC...NWC... LAT...LON 36008294 35828264 35978197 35728133 35278132=20 34578157 32898334 32148395 31228483 30578557=20 30678629 30748690 30648781 30868838 31728804=20 33378667 34558551 35118477 35458426 35958337=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) .