Subj : DAY3SVR: Nws Storm Prediction Center Norman Ok To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Mon Mar 18 2024 07:30:07 ACUS03 KWNS 180730 SWODY3 SPC AC 180728 Day 3 Convective Outlook NWS Storm Prediction Center Norman OK 0228 AM CDT Mon Mar 18 2024 Valid 201200Z - 211200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE WEDNESDAY AFTERNOON AND EVENING ACROSS PARTS OF THE TEXAS PANHANDLE AND ADJACENT WESTERN OKLAHOMA...AND WEDNESDAY NIGHT ACROSS THE TEXAS HILL COUNTRY VICINITY... ....SUMMARY... A couple clusters of thunderstorm activity may develop across the southern Great Plains late Wednesday afternoon into Wednesday night. Some of these storms could be accompanied by a risk for severe hail and gusty winds. ....Synopsis... As a significant short wave impulse, emerging from the base of larger-scale mid-level troughing centered near the Atlantic Seaboard, accelerates into the northern Atlantic, models continue to indicate that a less amplified split flow will gradually evolve east of the Rockies through the western Atlantic. Another vigorous short wave trough is forecast to continue digging within one branch, east-southeast of the Upper Midwest and Great Lakes region through much of the Northeast by the end of the period. It appears that the leading edge of an associated reinforcing low-level cold intrusion may advance through the southern Mid Atlantic coast vicinity and Tennessee Valley by 12Z Thursday, while advancing more slowly southward through the Ozark Plateau and central Great Plains. In another branch, a low amplitude wave emerging from the Southwest is forecast to progress into a lingering (but more weakly) confluent regime to the lee of the southern Rockies. It appears that surface troughing across the southern Great Plains will remain weak, with little in the way of substantive surface cyclogenesis. But an area of lower pressure may form in association with a remnant cyclonic vorticity center progressing into the Texas Panhandle vicinity by late Wednesday afternoon. In the wake of a prior intrusion of cool/dry air through much of the Gulf Basin, guidance continues to indicate that low-level moisture return off a modifying Gulf boundary layer will be limited, with better boundary-layer moisture not reaching the lower Rio Grande Valley/Texas coast until Wednesday night. ....Texas Panhandle vicinity... There is considerable spread concerning the evolution and progression of the approaching mid-level perturbation and the possible weak surface low development. But guidance generally suggests that forcing for ascent near/east of the low may ultimately support a developing cluster of thunderstorms by Wednesday evening. Preceding this development, surface dew points near the low may not increase much beyond 50 F. But, with daytime heating, a well-mixed boundary layer may become modestly deep, with CAPE increasing to around 500 J/kg, and perhaps locally up to 1000 J/kg, beneath relatively cold mid-level air including 500 mb temperatures around -20 to -22 C. Although lower/mid-tropospheric wind fields and deep-layer shear are forecast to become modest, at best, the environment may become supportive of strong initial convection which may pose a risk for marginally severe hail and wind. ....Central/Southern Texas... Beneath stronger southwesterly mid-level flow, more supportive of potential for organized severe convection, warm elevated mixed-layer air (based near or just above 850 mb) appears likely to strongly inhibit vigorous convective development, at least into Wednesday evening. Thereafter, mid/upper forcing for ascent and cooling with the approaching trough may sufficiently erode the inhibition to support thunderstorm initiation, with guidance generally suggesting highest probabilities across the Hill Country vicinity. Based on NAM forecast soundings, among other output, boundary-layer moisture may not be sufficient to support more than weak CAPE. But some severe hail in stronger storms may not be entirely out of the question, before convection becomes more widespread. ...Kerr.. 03/18/2024 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .