Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Apr 15 2023 16:32:29 ACUS01 KWNS 151632 SWODY1 SPC AC 151630 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1130 AM CDT Sat Apr 15 2023 Valid 151630Z - 161200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS MID-MS VALLEY TO NORTHERN LA... ....SUMMARY... Scattered swaths of severe thunderstorms are expected through tonight from the Mid-Missouri Valley to the Gulf Coast. Large hail and damaging winds will be the dominant hazards in terms of coverage, but a few tornadoes will be possible, especially across parts of Missouri and Arkansas. ....Mid MS Valley to the Gulf coast... A shortwave trough over the central Great Plains will shift east into the Mid-MS Valley through tonight. This trough has two embedded impulses, one across central KS and the other in eastern CO. The latter is expected to become dominant as the trough and attendant mid-level jet amplify, centered on this evening. The leading impulse will likely aid in initial surface-based thunderstorm development in the Ozark Plateau, immediately ahead of the primary surface cyclone along the northern return of richer boundary-layer moisture from eastern OK/western AR. Activity will expand northeast in MO, as well as develop south along and ahead of an eastward-moving cold front through AR to southeast TX. Weak low-level shear and rather modest hodograph curvature suggests that large hail will be the primary initial threat. Significant severe hail will be possible owing to very steep mid-level lapse rates initially and ample buoyancy amid 30-40 kt effective bulk shear. How quickly storms grow upscale from discrete supercells into a QLCS is somewhat uncertain, but is most likely to occur first across MO/northern AR towards the Mid-MS Valley in the late afternoon to early evening. This will yield a corresponding increase in the damaging wind threat. The 12Z NAM is substantially stronger than the 15Z RAP and 00Z ECMWF with the degree of low-level mass response ahead of the line in the early evening, lowering confidence in the degree of embedded tornado threat. The northern line of storms will weaken into tonight as storms spread east of the Mid-MS Valley amid diminishing buoyancy with eastern extent. Farther south, a messier mix of semi-discrete supercells and clusters might evolve into a southeast-moving QLCS spreading across the Lower MS Valley tonight. Low confidence exists in this scenario given potential for multiple rounds of convection this afternoon and evening. An ongoing MCS across LA/far southern MS may continue east along the central Gulf Coast with a primary threat of strong to isolated severe gusts. The track of this MCS this morning has yielded a swath of convective overturning in its wake, suggesting that weak low-level warm theta-e advection along/atop its residual outflow could support redevelopment of scattered storms around peak heating. Deep-layer vertical shear will be weaker with southern extent, but steep lapse rates and large undisturbed warm-sector CAPE will support potential for large hail/damaging winds late this afternoon/evening. ...Grams/Thornton.. 04/15/2023 $$ = = = 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) .