Subj : DAY2SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 23 2023 17:27:22 ACUS02 KWNS 231727 SWODY2 SPC AC 231725 Day 2 Convective Outlook NWS Storm Prediction Center Norman OK 1225 PM CDT Thu Mar 23 2023 Valid 241200Z - 251200Z ....THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS OVER PARTS OF THE LOWER MISSISSIPPI VALLEY... ....SUMMARY... Severe thunderstorms are likely from the Lower Mississippi Valley toward the lower Ohio Valley Friday afternoon and evening. Tornadoes, some strong, as well as damaging winds and hail are expected. ....Synopsis... A shortwave trough with positive tilt will move across the Southern Plains on Friday, and into the middle MS/lower OH Valley by Saturday morning. The primary zone of cooling aloft will remain roughly along and north of a Texarkana to Memphis to Evansville line, but height falls will occur even south of the jet core toward the northern Gulf Coast. This wave will impinge upon a prominent upper high over the Southeast, with a leading anticyclonically curved jet lifting north across the OH River and toward the Upper Great Lakes. The combination of differential divergence and low-level warm advection looks to be maximized from the Ozarks into the lower OH Valley from 21 to 06Z. Coincidentally, the surface low will deepen most after 00Z as it moves from northern AR northeastward up the OH Valley overnight. The low will move along an existing synoptic front, with a northward-jumping warm front possible just ahead of the low track from far southeast MO/southern IL into southern IN after 00Z. A cold front will develop behind the low, with low-level convergence maximized from northeast TX into western AR by 00Z, pushing east across northern MS and western TN/KY after 06Z. More subtle convergence is anticipated over southern portions of the warm sector across the Sabine River and into LA. The warm sector will be characterized by mid 60s F dewpoints from the low track southward, with upper 60s to 70 F likely into northern LA and central MS. Strong deep-layer shear will overspread the region, with increasing low-level shear developing late in the day/evening from the lower MS valley to the OH Valley as 850 winds increase into the 50-70 kt range. ....Western and northern AR into the OH Valley... Early day storms will be ongoing from eastern OK across northern AR and toward the OH River along and north of a surface front in a zone of glancing warm advection with a veered low-level jet. Some of this activity could contain hail from OK into AR given elevated MUCAPE over 1000 J/kg and long hodographs. In the wake of the earlier activity, diurnal storms are expected to form near the surface low and front extending south across western AR by mid afternoon, with additional activity extending northeastward along the developing warm front into southeast MO and to the OH River. Supercells may mature over AR, producing tornadoes especially later in the day toward 00Z as the low-level jet strengthens rapidly. This threat will expand quickly northeastward across the OH Valley, with a corridor of tornado or damaging winds anticipated near the surface low track. Given the very strong shear Friday evening, minimal uncapped surface-based instability will be needed to produce significant severe storms. As additional model guidance arrives and better observations exist into the Day 1 period, it is plausible that parts of the Moderate Risk could be extended/shifted northward a bit across AR given the more favorable large-scale lift over northern areas. ....Lower MS Valley... The air mass will destabilize across this area well into the evening, which will remain open warm sector with the cold front stalling to the west. Severe weather is most likely late in the day and evening as low-level moisture remains favorable, gradual cooling aloft occurs, and the low-level shear increases substantially. The fact that convergence will be subtle may be beneficial to the supercell tornado threat, and deepening bands of convection may eventually produce tornadoes from northern LA into central MS. Even if storms in this area remain isolated, impressive hodographs with 0-1 SRH over 300 m2/s2 will favor supercells and tornadoes, perhaps tracking for long distances given the lack of cold/stable air. Therefore despite perhaps a weaker model signal over these southern areas, the Moderate Risk has been maintained. ...Jewell.. 03/23/2023 $$ = = = 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) .