Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Sep 25 2025 19:57:00 ACUS01 KWNS 251956 SWODY1 SPC AC 251955 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0255 PM CDT Thu Sep 25 2025 Valid 252000Z - 261200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF THE NORTHEAST...MID ATLANTIC AND SOUTHWEST... ....SUMMARY... Scattered thunderstorms are expected from the Southeast to southern New England today. Isolated damaging winds and perhaps a tornado or two will be possible with some of this convection. Additional thunderstorms posing a risk for marginally severe hail and wind may occur across parts of the Southwest. ....20z Update... No major changes will be made to the valid outlook. Scattered, occasionally severe, storms are likely ahead of the cold front into early this evening across parts of the Mid Atlantic and Southern New England. Very moist surface conditions (low 70s F surface dewpoints) and intermittent warming amidst cloud cover is supporting weak instability. A low-topped band of showers and storms along the cold front in eastern PA and western NY should continue eastward into this evening. A few stronger updrafts with transient rotation remain possible. Isolated damaging gusts and a brief tornado are possible. See the previous discussion and MCD#2128 for additional information. ....Southwest... A few severe storms are also possible over parts of the Southwest through this evening. Initially tied to the higher terrain, storm coverage should gradually increase from southern AZ into NV and Southwest UT this afternoon. Modest buoyancy (MUCAPE 500-1000 J/kg) and 20-30 kt of vertical shear beneath the upper low should support a few more persistent storms with an isolated hail/wind threat. A few stronger storms may linger this evening as modest mid-level destabilization continues beneath the upper low. See MCD#2129 for updated sort-term forecast information. ...Lyons.. 09/25/2025 ..PREV DISCUSSION... /ISSUED 1119 AM CDT Thu Sep 25 2025/ ....Southeast States into Southern New York/New England... Recent satellite imagery reveals a large positively tilted upper trough that extends from the southern Plains through the Upper Great Lakes. Recent surface analysis places a large area of lower pressure from the north-central Gulf into eastern Ontario/southern Quebec, just ahead of the upper troughing. Two surface lows were analyzed at 14Z, one over western TN and another over central PA, with modest troughing extending between these two lows. A warm front also extends east-northeastward from the central PA across southern New England. This warm front is demarcated well by the 70 deg F isotherm. Scattered to numerous thunderstorms are anticipated from the Southeast into southern New England as the both the surface troughing and parent upper trough gradually progress eastward. A belt of stronger mid-level flow currently exists throughout the eastern periphery of the upper trough, extending roughly from central MS into the northern Mid-Atlantic. Northern portion of this stronger mid-level flow will spread gradually eastward/northeastward throughout the day into more of New England while the southern portion over the Southeast and Mid-Atlantic weakens. Rather poor lapse rates aloft and cloud cover/ongoing precipitation will delay/hinder diurnal destabilization across much of the warm sector today. A weakly unstable airmass is still anticipated along/ahead of the front from the Mid-Atlantic northward into southern New England, supporting continued thunderstorm development through the afternoon/early evening. Given the largely line-parallel orientation to the deep-layer shear, a predominantly linear storm mode is anticipated. Weak buoyancy coupled with the strengthening mid-level flow could support a risk for damaging gusts within any thunderstorm clusters that develop. Forecast wind profiles do show sufficient low-level shear for a tornado risk with any more persistent, cellular storms from eastern PA into southern NY. However, limited destabilization due to abundant cloud cover and poor lapse rates suggests shallow and transient warm sector updrafts, with linear development on the front more probable. ....Southwest... The well-defined cyclone currently moving across central CA is forecast to continue southeastward, eventually interacting with the moisture in place from eastern southern CA and the Lower CO Valley into western/southern AZ. A modest increase in mid-level west-southwesterly flow should occur ahead of this cyclone through the day, in tandem with increasing large-scale ascent overspreading parts of the Southwest. Scattered to numerous thunderstorms are expected to develop initially over the higher terrain of AZ, and subsequently develop slowly northward through the evening. Modest buoyancy and shear may support an isolated hail/wind threat with any more persistent convection that develops, especially where low-level lapse rates can become steepened through diurnal heating/mixing of the boundary layer. $$ = = = 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) .