Subj : DAY1SVR: Day 1 Convective Outlook To : wx-storm@lists.illinois.edu From : COD Weather Processor Date : Fri Jun 13 2025 19:59:22 ACUS01 KWNS 131959 SWODY1 SPC AC 131957 Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0257 PM CDT Fri Jun 13 2025 Valid 132000Z - 141200Z ....THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FOR PARTS OF CENTRAL AND SOUTHERN MONTANA... ....SUMMARY... Scattered severe thunderstorms are expected this afternoon and evening across parts of Montana, extending southward across portions of the central/southern High Plains. The greatest concentration of severe thunderstorms should occur across central/southern Montana, where large to very large hail, severe winds, and a couple tornadoes will be possible. ....20z Update... The forecast largely remains on track with only minor adjustments required for this update. ....Lower MS River Valley... Wind probabilities have been trimmed behind a broken line of convection spreading eastward into far eastern MS. Behind this line, an expansive cold pool/convective overturning has sufficiently reduced buoyancy to limit the potential for additional severe convection. Ahead of the cold pool to the northeast, the convective environment remains supportive of at least an isolated wind threat (see MCD #1272 for additional details). ....Southern High Plains... Wind probabilities have been expanded westward closer to the higher terrain across NM. Early attempts at sustained convection are ongoing from south-central CO into southern NM per latest visible imagery. Although moisture quality immediately off the terrain remains very limited (dewpoints in the upper 40s/low 50s), deep boundary-layer mixing denoted by 40-50 F dewpoint depressions may promote downdraft accelerations with an attendant severe wind risk. The past several HRRR/RRFS solutions have consistently shown a signal for at least sporadic severe gusts with this early convection. Severe gusts should become more probable with eastward extent later this evening as convection migrates into the deeper moisture along the NM/TX border. ....Central Oklahoma to western Arkansas... Early-morning convection has largely eroded across OK and far western AR; however, surface observations and visible imagery reveal a residual outflow boundary/differential heating zone draped from north-central OK to western AR. Some building cumulus is noted as temperatures warm into the upper 80s within a very moist air mass. The KSRX and KINX VWPs continue to sample 30-35 knot mid-level flow, which may be sufficient for organized cells if convection can develop along this boundary later this afternoon/evening. Additionally, increasing isentropic ascent between 925-850 mb late tonight may support additional thunderstorms across OK. ...Moore.. 06/13/2025 ..PREV DISCUSSION... /ISSUED 1126 AM CDT Fri Jun 13 2025/ ....Central/southern MT this afternoon/evening... Embedded speed maxima will progress east-northeastward over the northern Rockies, with associated bands of ascent denoted by weak convection now over ID. Surface heating along and southwest of a baroclinic zone oriented from north central into southeast MT, and arrival of the bands of ascent from ID will contribute to thunderstorm development by early afternoon over the higher terrain of southwest MT. Storms will then spread eastward through the afternoon/evening, in an environment supportive of supercells on the northeast edge of the steeper midlevel lapse rates, in a corridor with long hodographs/effective bulk shear in excess of 50 kt. The strong deep-layer shear and moderate buoyancy (MLCAPE near 1500 J/kg) will favor large hail production, some greater than 2 inch diameter with the supercells, as well as damaging outflow gusts that could reach or exceed 75 mph. A couple of tornadoes will also be possible, though relatively deep mixing and relatively straight hodographs cast some doubt on the tornado threat. ....High Plains this afternoon into early tonight... Despite being near the crest of the midlevel ridge, sufficiently moist, low-level upslope flow and steep midlevel lapse rates will support thunderstorm development near and east of the lee trough from eastern WY to eastern CO/western KS and the northern TX Panhandle later this afternoon/evening. Deep mixing, steep lapse rates, and relatively weak vertical shear all support initial storms growing upscale into clusters through outflow interactions, and the clusters will spread southeastward into tonight. Isolated large hail will be possible with the stronger embedded storms, while severe outflow gusts will become the main concern with storm clusters this evening into early tonight. ....MS/AL to KY this afternoon... East of a weak midlevel trough from east TX to MO, modest enhancement of midlevel flow (to roughly 30-35 kt) and daytime heating of a moist air mass will contribute to scattered thunderstorm development through the afternoon from southeast LA/MS across northwest AL, TN and KY. MLCAPE of 1500-2500 J/kg and the aforementioned enhancement to midlevel flow will support storm clusters/line segments with some potential for isolated wind damage this afternoon. ....Mid-Atlantic this afternoon... Strong surface heating is underway to the south of a slow-moving front from DE into northern MD, which will steepen low-level lapse rates and boost MLCAPE to 1000-1500 J/kg this afternoon. Scattered thunderstorm development is possible along the front and the Blue Ridge, and storms will spread eastward through late afternoon/evening. The moderate buoyancy, steep low-level lapse rates and modest deep-layer vertical shear (effective bulk shear of 25-30 kt) will support some storm/cluster organization and the potential for isolated wind damage. $$ = = = 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) .