Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Tue Nov 29 2022 12:58:35 ACUS01 KWNS 291258 SWODY1 SPC AC 291256 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0656 AM CST Tue Nov 29 2022 Valid 291300Z - 301200Z ....THERE IS A MODERATE RISK OF SEVERE THUNDERSTORMS FROM NORTHEASTERN LOUISIANA ACROSS CENTRAL MISSISSIPPI... ....SUMMARY... Tornadoes, very large hail, and severe wind gusts are expected this afternoon into the overnight period across parts of the lower to mid Mississippi Valley, Mid-South and parts of the Southeast. A few strong tornadoes will be possible. ....Synopsis... In mid/upper levels, a high-amplitude trough, bracketed by broadly cyclonic flow, will shift eastward from the Intermountain region and Rockies across the Plains States. By 00Z, the trough should extend from a cyclone over eastern MB, to eastern SD, central KS, and the southern High Plains. The trough should acquire negative tilt overnight as the cyclone moves eastward to northwestern ON, slower than the remainder of the trough across WI and IL to the Mid-South region. A related surface low was drawn at 11Z between CNK-BIE, with cold front southwestward across the OK Panhandle and northeastern corner of NM. A dryline preceded the front from southern OK across west- central TX and northern Coahuila. By 00Z, the low should reach northern WI, with cold front over western IL, south-central MO, southeastern OK, north-central TX, and southeastern NM. BY the end of the period, the front should reach eastern parts of OH/KY/TN, to central/southwestern AL, southeastern LA, and across parts of the northwestern Gulf to deep south TX. The cold front and dryline each will have minimal, if any, direct impact on severe convective processes through most of the period, though strong/isolated severe convection may develop overnight on the front, in the IL/ southeastern MO region. The bulk of severe activity instead will occur in the moist/warm sector as discussed below. However, a more-influential marine warm front -- drawn initially over south-central/southeast TX, coastal LA, and the northeastern Gulf -- will move diffusely inland through LA/AR/MS and the Mid-South today. This front will redevelop/ reorient northwest/southeast this evening, then north-northwest/ south-southeast overnight from the lower Ohio Valley across central/eastern Al and the FL Panhandle. ....Lower Mississippi Valley to Lower Ohio Valley and central Gulf Coast... Multiple rounds of severe thunderstorms -- some capable of long- tracked tornadoes with EF3+ damage potential -- will be possible this afternoon into tonight over parts of the lower Mississippi Valley region and Mid-South. Large, locally damaging hail and strong-severe thunderstorm gusts also are expected over the region. With low-level and deep shear each favorable area-wide, instability and convective coverage/mode will be the main regulators of severe potential. Isolated to widely scattered, surface-based thunderstorms -- including several supercells -- will develop as early as midday over southwestern parts of the outlook area, over parts of east TX into portions of western/northern LA. This will occur as a broad area of subtle but persistent low-level lift, both from mass convergence and modest diabatic heating, act together to weaken a stable layer between 700-850 mb. Some progs indicate relative weakness in low-cloud cover in the corridor from central LA into central MS this afternoon, which may focus potential further by virtue of creating a differential-heating zone. Either way, MLCINH should be made negligible through late afternoon into evening, supporting a growing amount of surface-based development into southeastern AR, southwestern TN, and MS with time. Additional development is possible near and south of the marine front over southern parts of AL/MS into the western FL Panhandle. The warm sector will continue to expand over MS/AL and western TN this evening prior to cold frontal passage, into AL overnight. MLCAPE of 1000-2000 J/kg should become common outside areas of convection, from eastern AR and southwestern TN toward the Gulf Coast. The warm sector will narrow with northward extent, containing weaker moisture content as well as lower temperatures across southeastern MO, western KY, and southern parts of IL/IN. Still MLCAPE near 500 J/kg is expected to support isolated wind, tornado and hail potential there. A broad, southwesterly LLJ will contribute to large, well-curved hodographs with effective SRH commonly 300-500 J/kg. As the trough approaches and gradient flow aloft strengthens, effective-shear magnitudes will as well, reaching 50-60 kt late this afternoon into evening over much of the region. This will help the supercell threat to persist well into the overnight hours over MS/AL, but with convective mode overall likely getting messier. Late overnight, with eastward extent from AL into GA and the western FL Panhandle, the eastward progress of the main convective regime is expected to outpace that of the warm sector. Activity will move over a progressively less-favorable boundary layer characterized by lower theta-e eastward. The eastern rim of the threat will be fuzzy and not sharp-edged, however, and itself will be moving slowly eastward at the end of this period and into early day 2. ...Edwards/Mosier.. 11/29/2022 $$ = = = 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) .