Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 13 2025 19:31:28 ACUS03 KWNS 131931 SWODY3 SPC AC 131930 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0230 PM CDT Thu Mar 13 2025 Valid 151200Z - 161200Z ....THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS IN EASTERN LA...MS...AND AL... ....SUMMARY... A severe weather outbreak is expected on Saturday across the central Gulf Coast States and Deep South into the Tennessee Valley. Numerous significant tornadoes are possible on Saturday afternoon and evening, centered on eastern Louisiana, Mississippi, and Alabama. Widespread damaging wind swaths and scattered large hail are likely. ....Central Gulf Coast/Deep South/TN Valley... Primary change is to expand level 4-MDT north in AL and all categories west in the tight gradient of severe potential from the Sabine to Lower MS Valleys. A particularly volatile scenario for destructive severe remains evident during the afternoon to evening on Saturday centered on the level 4-MDT risk region. In the wake of the vigorous shortwave trough and very deep surface cyclone crossing the North-Central States on D2, a broad upper trough will linger across the southern Great Plains. An intense mid-level jetlet, in excess of 100 kts at 500-mb, should eject through the basal portion of this trough in south TX on Saturday afternoon. This will induce secondary cyclogenesis along the slow-moving baroclinic zone from the Ark-La-Tex to the central Great Lakes. Another day of air mass modification ahead of this wave will yield a pronounced plume of rich northwest Gulf moisture that should be pristine across southeast LA into central MS through late morning. As mid-level height falls overspread the diurnally warming air mass, increasing convective development is expected along the deepening baroclinic zone, as well as residual outflows to its northeast in the TN Valley from prior late D2 convection. Steep mid-level lapse rates atop the richly moist boundary layer should yield at least moderate MLCAPE across the Lower MS Valley. Vertically veering wind profiles with strong anvil-level divergence amid the favorable instability should support robust updrafts and intense supercells. Low-level shear will strengthen during the afternoon and evening, setting the stage for a severe-weather outbreak including significant tornadoes, damaging gusts, and large hail. A pronounced dropoff in severe may be realized with northward extent across the TN Valley as an emerging band and/or highly organized line outpaces the rich Gulf air. Despite weaker instability with eastern extent into GA/SC, the intense wind fields may sustain damaging wind and embedded tornado potential well into the overnight. ....OH Valley to Lower Great Lakes... Forecast confidence is low with regard to severe potential north of the TN Valley. Weakening late D2 convection should be in a decaying process at 12Z Saturday. Much of the region will then be in between waves until late afternoon. Guidance differs on the degree of diurnal destabilization ahead of the deepening surface cyclone that should track north-northeast from the Ark-La-Tex. It is plausible that widespread Mid/Deep South to TN Valley convection during the day Saturday will temper the northward extent of instability by Saturday evening/night within a predominately meridional deep-layer wind profile. As such, the overall severe risk appears conditional, but given the fast flow regime, potential for damaging winds and perhaps a few tornadoes may be realized. ...Grams.. 03/13/2025 $$ = = = 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) .