Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Thu Jun 12 2025 05:52:37 ACUS01 KWNS 120552 SWODY1 SPC AC 120550 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1250 AM CDT Thu Jun 12 2025 Valid 121200Z - 131200Z ....THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS TODAY INTO TONIGHT ACROSS PARTS OF THE GREAT PLAINS...THE UPPER MIDWEST...SOUTHEASTERN TEXAS INTO THE LOWER MISSISSIPPI VALLEY AND PARTS OF THE NORTHERN MID ATLANTIC... ....SUMMARY... Scattered areas of strong thunderstorm development are possible today into tonight, accompanied by potential for severe hail and wind across parts of the Great Plains, the Upper Midwest, the Texas coastal plains into lower Mississippi Valley and a small portion of the northern Mid Atlantic. ....Discussion... Split westerlies across the mid- and higher latitudes of the eastern Pacific into North America include broad, weak troughing across the northeastern Pacific into British Columbia and the Pacific Northwest. Models suggest that this cyclonic flow may undergo some amplification later today through tonight, as an embedded short wave perturbation pivots into the Pacific Northwest, to the south of a slow moving low near/offshore of the northern British Columbia coast. Downstream, short wave ridging is forecast to shift across the Canadian Prairies and east of the northern U.S. Rockies. However, it appears a residual belt of (relatively) stronger flow will linger above a stalled frontal zone across parts of the middle Missouri Valley, into a confluent regime across the northern Mid Atlantic, to the south of large-scale mid/upper troughing across the eastern Canadian provinces. It appears that seasonably high moisture content will largely remain confined to the southern mid- and subtropical latitudes, where ridging will remain suppressed, but westerlies will remain modest to weak. One larger-scale trough within this regime is forecast to slowly shift east of the southern Great Plains and northwest Gulf coast, toward the Mississippi Valley today through tonight. ....Northern Rockies into Upper Midwest... Despite seasonably modest boundary-layer moisture, models indicate that lower/mid-tropospheric lapse will become sufficiently steep to support at least pockets of mixed-layer CAPE in excess of 1000 J/kg, along/south of the stalled frontal zone across the Big Horns and Black Hills vicinity into the Upper Midwest, and within lee surface troughing across/northeast of the Cheyenne Ridge. Aided by forcing for ascent and shear associated with a couple of smaller scale mid-level perturbations/speed maxima (40-50+ kt at 500 mb) progressing through the belt of westerly flow, the environment may become conducive to organized convective development this afternoon and evening. This may include widely scattered supercells and small upscale growing clusters posing a risk for severe hail and wind. ....Northern Mid Atlantic... The development of mixed-layer CAPE on the order of 1000-2000 J/kg also appears possible with daytime heating of a moistening boundary-layer, along the southern slopes of the higher terrain of north central through northeastern Pennsylvania by late this afternoon. Although forcing for ascent to support thunderstorm initiation remains unclear, deep-layer shear beneath the southern fringe of seasonably strong westerlies will likely be conditionally supportive of organized convection capable of producing severe hail and wind, before the instability wanes late this evening. ....Southern Rockies into adjacent Great Plains... Downstream of the large-scale mid/upper troughing developing inland of the Pacific coast, models indicate a generally weak but difluent downstream flow will prevail across the southern Rockies. There is a notable signal within the model output that forcing for ascent will become supportive of widespread thunderstorm development along the Front Range and Sangre de Cristo Mountains by mid to late afternoon. Although propagation off the higher terrain will probably be initially slow, due to modest downstream destabilization, model forecast soundings indicate that a warm and deeply mixed boundary layer will become supportive of a few strong downbursts to the lee of the higher terrain. Consolidating and strengthening outflow may support strengthening surface cold pools with a continuing risk of strong to severe gusts into portions of the adjacent high plains through this evening. ....Texas Coastal Plains into lower Mississippi Valley... An increase in thunderstorm development gradually continues across and east of the I-35 corridor of central Texas, aided by forcing for ascent associated with a short wave impulse progressing through the weak larger-scale mid-level trough. It appears that this will continue into the Texas coastal plain, where inflow of seasonably high moisture content characterized by sizable CAPE may support considerable gradual further intensification through 12Z. To differing degrees, the various model output suggests that this may be accompanied by a developing lower/mid-tropospheric cyclonic circulation, and associated augmentation of the wind fields, that will tend to advect north-northeastward toward the Ozark Plateau/Mid South today. Preceded by a developing corridor of moderately large CAPE with daytime heating, it is possible that the environment could become conducive to organizing convection with potential to produce strong to severe surface gusts, and perhaps potential for a couple of brief tornadoes. ...Kerr/Squitieri.. 06/12/2025 $$ = = = 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 3.20-Linux * Origin: capitolcityonline.net * Telnet/SSH:2022/HTTP (1:2320/105) .