Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Sat Sep 13 2025 05:45:58 ACUS01 KWNS 130545 SWODY1 SPC AC 130544 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1244 AM CDT Sat Sep 13 2025 Valid 131200Z - 141200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS FROM THE SOUTHWEST TO THE DAKOTAS AND IN A PART OF THE MIDWEST... ....SUMMARY... Isolated severe wind and hail will be possible from the Southwest/southern Rockies to the northern Great Plains and a portion of the Midwest, mainly today into early tonight. ....Southwest/southern Rockies/High Plains... The basal portion of the broad mid/upper trough from the northern Rockies to the Lower CO Valley will progress more quickly east, yielding an elongated trough enveloping the entire High Plains by early Sunday. Widespread thunderstorm development is anticipated by midday to early afternoon across western NM/CO as cooling mid-level temperatures become favorably timed with moderate diurnal heating of a seasonably moist airmass. Lower-level instability should be tempered by remnants of early morning convection and the quick redevelopment cycle by afternoon. Nevertheless, a broad belt of moderate southwesterly speed shear should support transient mid-level updraft rotation within the deepest updrafts. These should tend to become focused across southern/eastern NM later in the afternoon, but this region will be on the fringe of greater mid-level cooling centered on the Four Corners. As such, mid-level lapse rates will be weak where boundary-layer heating is more pronounced. A broad swath of sporadic strong to marginally severe hail/wind is anticipated before convection subsides after sunset. ....NE/SD/ND... Overall severe wind/hail potential appears low across multiple regimes through the period, amid a persistent meridional mid-level flow regime. Ongoing convection over the western Dakotas, tied to a minor MCV, should progress north-northeast towards the Canadian border this morning. Residual cloudiness/overturning should limit the northern extent of more substantial diurnal destabilization in ND. Late afternoon to evening storm development appears more likely to emanate out of the central High Plains north-northeastward across western/central NE within a modestly sheared and weakly buoyant airmass. This activity may foster another MCV that drifts north into SD, which could impinge on a confined corridor of recovered moderate buoyancy and sustain a marginal severe wind/hail threat tonight. ....IL/IN/WI... Low-probability severe hail/wind potential remains evident, but seems likely to be rather isolated. An MCV over central WI will drift south-southeast this morning. An increase in convective vigor is possible towards sunrise along the MUCAPE gradient in southern WI to northern IL. Within a belt of moderate mid-level northwesterlies, transient/weak updraft rotation is possible in a cell or two. Guidance differs greatly on the degree of boundary-layer heating downstream of the morning elevated activity. The more aggressively warm guidance suggests a conditional threat of diurnal intensification with potential for locally strong gusts. ...Grams/Dean.. 09/13/2025 $$ = = = 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) .