Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Mar 23 2023 12:40:49 ACUS01 KWNS 231240 SWODY1 SPC AC 231239 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0739 AM CDT Thu Mar 23 2023 Valid 231300Z - 241200Z ....THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS BETWEEN THE OZARK AND EDWARDS PLATEAUS... ....SUMMARY... Severe thunderstorms with large, locally very large and destructive hail will be possible this afternoon into tonight between the Ozark and Edwards Plateaus. Isolated severe gusts or a tornado are possible as well. ....Synopsis... A series of mid/upper-level shortwave perturbations will reinforce and traverse a progressive troughing regime over the western CONUS. The most important of those for this forecast is a basal shortwave trough now evident in moisture-channel imagery over central/southern AZ, southwestward across northern Baja. This perturbation and its associated vorticity field will deamplify gradually by 00Z, while ejecting east-northeastward to eastern/southern NM and northern Chihuahua. By 12Z, the perturbation should become diffuse over MO, amidst strong southwest flow that will persist downstream from the synoptic trough back across the Four Corners area to northwestern MX. At the surface, 11Z analysis depicted a slow-moving cold front from southeastern Lower MI across central IL to a weak low near COU, then over southeastern KS, western OK, and the northern TX Panhandle. The cold front is expected to move slowly southward across parts of the Ohio Valley, Ozarks, OK, and northwest TX through the period. Its baroclinicity will be reinforced and shunted southward on the mesoscale by a series of thunderstorms developing along and behind the front as described below. By 00Z, the effective front should reach southern portions of IL/IN/MO, south-central/southwestern OK, and the central TX Panhandle, where it will intersect a Pacific front that will have exited the southern Rockies during the day. The latter front should reach the southern Caprock, Permian Basin and Davis Mountains regions around 00Z. Both fronts will overtake the dryline this evening and tonight. By 12Z, the combined frontal zone should extend roughly along the Ohio River from northern KY southwestward, then over northwestern AR, southeastern OK, western north TX, and the Edwards Plateau. ....Southern Plains to Ozarks/lower Ohio Valley... Scattered to locally numerous thunderstorms should form this afternoon and early evening along and behind the front across the Ohio Valley region, MO and OK, with more isolated/conditional development potential into stronger MLCINH over northwest TX near the front/dryline intersection. While any of this activity may produce severe hail and isolated strong-severe gusts, the main threat will be over parts of OK into northwest TX. Over the latter areas, any persistent thunderstorms in a greater instability/shear parameter space will have the potential to become supercells and offer significant/2+ inch diameter hailstones. As the front(s) overtake the dryline this evening and tonight, the combined lift may overcome EML-related CINH enough to backbuild the convection into parts of west-central and perhaps southwest TX. At least isolated thunderstorms (which also may become supercellular and offer substantial hail) are possible as far south as the Rio Grande. The outlook is more uncertain with southward extent from the Red River region, as generally lesser storm coverage is expected over TX. However, conditional potential exists for very large and destructive hail from any sustained convection in the area. Meanwhile, activity across OK and perhaps northwest TX should merge into at least a loosely quasi-linear complex, with training echoes and repeated bouts of severe hail possible in some locales. Any development that can mature along/ahead of the front, without getting undercut by it, may pose damaging-gust and marginal tornado threats too, though hodograph size and SRH will be limited by modest wind speeds near the surface. Forecast soundings suggest favorable deep shear for supercells, with intense (50-70 kt) winds in the 400- 600-mb layer contributing to effective-shear magnitudes in the 55- 70-kt range. A combination of persistent low- and high-level cloud cover will temper diurnal heating somewhat. Still, with low/middle 60s F dewpoints pervasive in the moist sector, peak/preconvective MLCAPE around 1500 J/kg should be common from the Ozarks southwestward, diminishing below 1000 J/kg toward southern IN and locally reaching 2000 J/kg in parts of southwestern OK and northwest TX. As hodographs enlarge somewhat this evening beneath a 30-40-kt LLJ, the prefrontal boundary layer will stabilize gradually, with the offsetting factors keeping overall wind/tornado threat marginal overnight, despite more-linear mode and potentially larger SRH. ...Edwards/Dean.. 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) .