Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Apr 20 2023 19:32:43 ACUS01 KWNS 201932 SWODY1 SPC AC 201931 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0231 PM CDT Thu Apr 20 2023 Valid 202000Z - 211200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON AND EVENING IN A CORRIDOR FROM SOUTHERN WISCONSIN THROUGH THE MIDDLE MISSISSIPPI VALLEY AND SOUTHEASTERN GREAT PLAINS... ....SUMMARY... Scattered severe thunderstorms remain possible late this afternoon and evening in a corridor from from southern Wisconsin to south Texas. Damaging winds and large hail appear the primary hazards in terms of coverage, but a few tornadoes are also possible. ....20Z Update... Large-scale mid-level troughing now east of the Rockies may amplify a bit further, but only a slow eastward progression into the Mississippi Valley is expected through early Friday. An associated modestly deep cyclone appears likely to continue to gradually occlude across the Upper Midwest and adjacent Great Lakes vicinity, with the trailing cold front advancing into the lower Great Lakes, lower Ohio, Mississippi and Rio Grande Valleys. Due to the lingering presence of mid-level troughing across the Florida Peninsula, and dry/potentially cool boundary-layer air associated with surface ridging across much of the Southeast and eastern Gulf of Mexico, low-level moisture return to the warm sector of the cyclone remains rather modest. Seasonably moist boundary-layer air remains largely confined to southern/central and eastern Texas, where south through southwesterly flow in the lower/mid troposphere has become modest to weak, in the wake of the cyclone. As a result, while conditions have become conducive to increasing vigorous thunderstorm development posing at least some risk for large hail, damaging wind gusts and tornadoes, in a pre-frontal corridor from Texas through southern Wisconsin, severe weather potential overall does not appear particularly optimized. Severe probabilities are being maintained as outlined in the 1630Z, aside from some change to account for the progression of the synoptic features. ...Kerr.. 04/20/2023 ..PREV DISCUSSION... /ISSUED 1126 AM CDT Thu Apr 20 2023/ ....Mid-MS Valley to southern WI... Elevated convection persists across portions of southern WI and IL, but appears to be weakening. Subsidence in its wake has yielded cloud breaks immediately ahead of the primary surface cyclone over central IA, which will yield destabilization into this afternoon across the Mid-MS Valley and IL to southern WI. The cyclone will initially track northeast into western WI before occluding northward, aided by an 80-90 kt 500-mb jetlet curling across IA into central WI. The degree of surface-based destabilization remains somewhat uncertain with a confined warm/moist sector ahead of the eastward-moving cold front. But guidance is largely insistent that a narrow plume of moderate MLCAPE of 1000-1500 J/kg should develop, as upper 50s to low 60s surface dew points in eastern IA and northeast MO advect northeast. The synoptic pattern will support strong effective bulk shear along with an enlarged low-level hodograph favorable for discrete supercells consolidating into small clusters. As such, have increased tornado probabilities and expanded the cat 2-SLGT risk northward. Otherwise, a mix of scattered large hail and damaging wind will be possible, but the overall threat will likely be spatially and temporally confined given the narrow warm/moist sector, resulting in severe potential rapidly weakening in the early evening roughly east of the IL/IN border longitude. ....Central/east TX to AR... The cold front surging south-southeast towards the Concho Valley of west-central TX and the Ozark Plateau is expected to help focus scattered to widespread thunderstorms along and ahead of it this afternoon and evening. Large buoyancy with MLCAPE in excess of 2500 J/kg, supported by steep mid-level lapse rates, will primarily reside across central to south TX where low-level shear should remain weak. But sufficient deep-layer shear, although somewhat parallel to the front, should support initial supercells consolidating into several clusters and one or more MCSs. Farther northeast across the Ark-LA-Tex into AR, low-level shear will be comparatively greater but buoyancy will be relatively less. Large hail can be expected with the more discrete storms (some in excess of 2 inch diameter, especially across central to south TX), and the potential for damaging winds will increase with upscale growth this evening. The tornado threat is expected to remain unfocused and short-lived, likely dependent on favorable storm-scale/boundary interactions. $$ = = = 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) .