Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 20 2025 05:17:51 ACUS01 KWNS 200517 SWODY1 SPC AC 200516 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1216 AM CDT Sat Sep 20 2025 Valid 201200Z - 211200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON INTO EVENING ACROSS PARTS OF THE SOUTH CENTRAL GREAT PLAINS... ....SUMMARY... Scattered strong thunderstorms may impact parts of the south central Great Plains late this afternoon and evening, accompanied by some risk for locally strong to severe wind gusts and perhaps some marginally severe hail. ....Discussion... In the northern mid-latitudes, flow across the Pacific appears likely to remain strong and zonal, with one significant short wave trough on the leading edge of this regime forecast to progress inland of the British Columbia and portions of Pacific Northwest coastal areas during this period. Downstream, models indicate that flow will remain more amplified across Canada into the northern Atlantic, with one significant trough and embedded cyclone slowly progressing offshore into the Labrador Sea/northwestern Atlantic vicinity. In the wake of this feature, the center of cool surface ridging is forecast shift from western Quebec into New England, with a ridge axis building south-southwestward to the lee of the Appalachians through much of the Atlantic Seaboard. In advance of the trough migrating inland of the Pacific, modest deepening of surface troughing appears possible as far south as the lee of the northern U.S. Rockies. However, much of the U.S. and adjacent interior southern Canada will generally remain under the influence of a weak split flow including larger-scale troughing in one branch across the northern Great Plains into Great Lakes/Ohio Valley, and troughing across the southern mid-/subtropical latitudes of the eastern Pacific and across the Southeast, within another branch. ....South Central Great Plains... Near the southwestern flank of the broad mid/upper troughing roughly centered across the mid/upper Mississippi Valley, it appears that boundary-layer destabilization may become characterized by moderately large CAPE in a pre-frontal corridor centered across the Texas Panhandle through northern Oklahoma by late this afternoon. As this maximizes, it appears that low-level convergence near modestly deepening surface troughing will support that initiation of scattered thunderstorm activity, perhaps aided by forcing for ascent associated with a subtle digging short wave perturbation. Although deep-layer wind fields and shear are forecast to be generally weak, forecast soundings characterized by relatively steep low-level lapse rates, including modestly deep boundary-layer mixing, appear conducive to localized strong to severe gusts and perhaps some marginally severe hail with stronger cells into early to mid evening. ...Kerr/Halbert.. 09/20/2025 $$ = = = 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 3.28-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .