SPC 1300Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 0752 AM CDT Thu May 15 2025 Valid 151300Z - 161200Z ...THERE IS AN ENHANCED RISK OF SEVERE THUNDERSTORMS ACROSS EAST-CENTRAL MINNESOTA...MUCH OF WISCONSIN...SOUTHERN AND WESTERN LOWER MICHIGAN...NORTHEAST ILLINOIS...NORTHERN INDIANA AND NORTHWEST OHIO... ...THERE IS A SLIGHT RISK OF SEVERE THUNDERSTORMS OVER PORTIONS OF VIRGINIA AND NORTHEAST NORTH CAROLINA... ...SUMMARY... Severe thunderstorms are expected across parts of the upper Mississippi River Valley and Great Lakes this afternoon and evening. Tornadoes, some of which could be strong, and very large hail and damaging winds will be possible. Severe thunderstorms are also expected through the lower Ohio River Valley, Ozarks and in parts of the Mid-Atlantic. ...Mid to Upper Mississippi Valley/Great Lakes/Ohio Valley... A deepening surface low will gradually consolidate as it moves north across the eastern Dakotas today, and a warm front will lift north through the OH Valley and into WI/Lower MI late this afternoon. As strong large-scale ascent develops in association with a northeast-moving/negatively-tilted upper trough and left exit region of a 300-mb jet streak, rapid thunderstorm development, or re-intensification of ongoing storms, is expected from near the surface low east/southeast along an arcing occluded/cold front over central MN/western WI/northeast IL. A broken line of semi-discrete cells is anticipated within a strongly unstable and amply-sheared environment supporting supercell storm structures. Large hail, possibly very large and in excess of 2.5 inches in diameter, will be possible in addition to damaging wind gusts. Low-level shear will support the potential for tornadoes with mature supercells, and the risk for strong tornadoes will exist, especially towards evening as low-level shear increases. Storms should tend to merge into clusters or line segments with time, especially across southern lower MI/northern IN/OH, where significant severe wind potential will exist with an eastward moving complex of storms. The 30% wind/sig severe wind area was extended east into southeast lower MI based on latest hi-res guidance. ...Ozarks... Thunderstorms have developed along the Red River in southeast OK/western AR this morning, along the southern periphery of stronger mid-level flow and with moderate elevated buoyancy. Although larger-scale forcing remains nebulous, these storms may continue to intensify and become surface based with time with the onset of diurnal destabilization. Strong southwesterly flow will contribute to ample deep-layer shear for supercells or a small cluster. Severe hail and perhaps wind will be the primary severe hazards as storms move across AR towards the mid-Mississippi Valley, and the Slight (Level 2) Risk has been extended southwest across northern AR for this potential. ...Central Appalachians/Mid-Atlantic... Scattered thunderstorms are expected to develop in response to diurnal heating and across the higher terrain this afternoon, and move southeast within an environment of moderate/locally strong surface-based instability and 35-40 kts of northwesterly deep shear. In this parameter space, supercell structures and clusters will be possible and pose a risk for large hail and damaging winds. Trends in the 00z HREF and early morning hi-res guidance were the basis for extending the Slight (Level 2) Risk southeast across portions of northeast NC. ..Bunting/Dean.. 05/15/2025