Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sun Apr 23 2023 12:44:40 ACUS01 KWNS 231244 SWODY1 SPC AC 231242 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0742 AM CDT Sun Apr 23 2023 Valid 231300Z - 241200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS OVER PARTS OF SOUTH TEXAS...INCLUDING THE LOWER RIO GRANDE VALLEY... ....SUMMARY... Severe wind gusts (some potentially exceeding 70 mph), large to very large hail, and a tornado or two are possible over south Texas into early/mid afternoon. ....Synopsis... The mid/upper-level pattern across the CONUS will continue to be dominated by a large, complex cyclone covering much of the Great Lakes, Ohio Valley, Upper Midwest, and ON. A weaker, but longer-lived circulation/vorticity center now moving northward from lake Huron is progged to move northward over Hudson Bay by the end of the period. Meanwhile, another low -- evident in moisture- channel imagery over ON just north of the MN border -- should meander erratically near its current position through tomorrow morning. These processes will maintain a broad swath of cyclonic flow from the Rockies across much of the Great Plains, Mississippi Valley and eastern CONUS. The most prominent embedded shortwave troughs -- initially over the lower Ohio Valley and lower Missouri Valley -- will pivot across the northern Appalachians and Ohio Valley, respectively. As that occurs, a surface occluded front -- analyzed at 11Z along the longitude of the Hudson Valley in NY -- will move slowly eastward over parts of New England, preceded by isolated thunderstorm potential in the elevated warm-advection conveyor. An offshore/triple-point low -- initially south of Long Island, will move eastward, with the trailing cold front moving slowly southward over the FL Peninsula and northeastern Gulf. The western part of this boundary was drawn from the northwestern Gulf across the CRP/COT areas, while being overtaken by a combination of growing convective processes and a reinforcing cold front near DRT. This boundary segment will serve as a northern focus/bound for substantial convection discussed below, through the afternoon. ....South TX... See SPC severe thunderstorm watch 164 and related mesoscale discussions for near-term guidance on convection organizing over south TX. An initially broken band of multicells and supercells between VCT, SAT and Maverick County is expected to expand and intensify through midday into a well-developed, bowing MCS, proceeding eastward to southeastward through downshear parts of south TX. Any sustained supercells in the meantime will pose a threat for large (perhaps significant/destructive) hail, severe gusts and a tornado or two. The major threat will become severe wind with time. Significant-severe (65+ kt) gusts may develop as the activity approaches the lower/middle TX Coast below VCT, and areas from Padre Island to the lower Rio Grande Valley. Forced ascent along the leading edge of the complex should encounter a favorably buoyant inflow environment mainly along and south of the quasistationary/marine front, with isolated large hail or strong- severe gusts possible north of the boundary. To its southeast, further low-level destabilization should occur in the lower Valley and near-coastal warm sector from diurnal heating. Accordingly modified RAOBs and forecast soundings show that the combination of steep low/middle-level lapse rates, upper 60s to mid 70s F surface dewpoints, and a deep troposphere contribute to preconvective MLCAPE in the 2000-3500 J/kg range -- comparable to MUCAPE values over parts of deep south TX now. Strong mid/upper-level westerlies aloft and a substantial surface easterly component will contribute to 45-55-kt effective-shear magnitudes. Strong storm-relative boundary-layer winds also are expected to develop -- further reinforced by accelerating storm motion. With support from those midlevel westerlies, a well- organized rear-inflow jet may develop, further sustaining the activity across deep south TX, then for a substantial distance across the Gulf. Given expected convective trends and the large reservoir of favorable moisture/instability in place, severe-wind probabilities have been upgraded across much of the overland warm sector. ...Edwards/Leitman.. 04/23/2023 $$ = = = 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) .