SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0737 AM CDT Tue Apr 29 2025 Valid 291300Z - 301200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS FROM PARTS OF WEST TX INTO SOUTHWEST OK...AND FROM THE OH VALLEY INTO THE LOWER GREAT LAKES... ...SUMMARY... Scattered severe thunderstorms are possible within a broad swath from the Lower Great Lakes to the southern High Plains, mainly during this afternoon to evening. Corridors of greater threat are expected over the Upper Ohio Valley/Lower Great Lakes and in parts of west Texas into southwest Oklahoma. ...Synopsis... Recent satellite imagery shows a well-defined shortwave trough moving through northwest Ontario and the adjacent Upper Midwest, and a mature cyclone centered over the central UT/AZ border. The northern shortwave trough is forecast to move eastward across the Great Lakes and eastern Canada today while also transitioning to a more negative tilt. The UT/AZ cyclone is expected to progress southeastward across AZ and into western NM as an embedded shortwave trough moves through its base across northern Mexico and into the southern High Plains. Early morning surface analysis places a low over eastern Lake Superior, with a cold front extending southwestward from this low into central OK where another, weaker surface low exists. The front continues westward from this second low across the TX Panhandle and through central NM. The northern low is forecast to progress eastward across eastern Canada, moving just ahead of its parent shortwave trough, ending the period over the Canadian Maritimes. The attendant cold front will also push eastward moving through the OH and TN Valleys, and much of the Northeast. Southern/western portion of the front will make limited southerly/southeasterly progress, with its position becoming more regulated by repeated convective outflow throughout the day. Numerous thunderstorms, some severe, are anticipated along the eastward progressing cold front from the OH Valley into the Lower Great Lakes and Northeast, as well as farther southwest across the southern Plains near the stalled boundary. ...Ohio Valley into the Lower Great Lakes... Ongoing cluster across northeast OK will continue through the Ozarks this morning before reaching the Lower OH Valley this afternoon. It seems probable that this cluster will reintensify as it interacts with the destabilizing airmass over the region. Additional thunderstorm development appears likely along the front north of this cluster throughout much of the OH Valley into the Lower Great Lakes. Strong low/midlevel flow will support development of organized storm clusters, along with some potential for discrete or embedded supercells. Scattered damaging winds will be possible, with some potential for swaths of more concentrated wind damage if any organized linear segments develop. The strongest low-level flow will be displaced north of the region, but 35-50 kt in the 850-700 mb layer will support sufficient low-level shear for some supercell and/or line-embedded tornado threat. Isolated hail could also accompany any persistent supercell structures. ...West TX into the Ozarks... Complex convective evolution is underway across OK this morning as a northeastward progressing convective cluster interacts with the thunderstorms that developed along the front over northwest/north-central OK. Current trends and recent guidance suggest that an MCS will evolve and then track northeastward across the Ozarks. The airmass downstream is expected to remain supportive of damaging gusts and large hail for at least the next few hours. Another round of thunderstorms is anticipated this afternoon both along the outflow-modulated cold front in OK and northwest TX and along the dryline in West TX as the airmass destabilizes. Strong buoyancy and shear will support supercells, particularly from west TX into southwest OK during the late afternoon where low-level convergence will be strongest. Large to very large hail will be the primary threat initially, but strong cold pools and close storm proximity should result in several clusters capable of strong to significant gusts. A mesoscale corridor of greater tornado potential may materialize just east of the surface low where stronger southeasterly low-level flow and higher low-level moisture may overlap. Current guidance suggests this would be over northwest TX, but uncertainty exists regarding the outflow/cold front and surface low positions, precluding the confidence needed to outlook higher tornado probabilities. ..Mosier/Jewell.. 04/29/2025