SPC 1200Z Day 1 Outlook
Day 1 Convective Outlook NWS Storm Prediction Center Norman OK 1246 AM CDT Sat Apr 12 2025 Valid 121200Z - 131200Z ...THERE IS A MARGINAL RISK OF SEVERE THUNDERSTORMS ACROSS PARTS OF SOUTHEAST MONTANA AND NORTHERN WYOMING... ...SUMMARY... Thunderstorms with isolated severe gusts are possible from the Big Horns to the Black Hills from this afternoon into the evening. ...Southeast Montana/Northern Wyoming/Western South Dakota... A shortwave mid-level trough will move eastward across the Pacific Northwest today, as an associated 50 to 60 knot jet streak translates eastward into the northern Rockies. Ahead of the trough, a surface low will deepen across eastern Wyoming, which will increase low-level convergence across parts of the northern High Plains. Surface dewpoints in the 40s F will contribute to weak destabilization. As surface temperatures warm, thunderstorm development is first expected in the Big Horn Mountains during the early afternoon, with these storms moving eastward into the lower elevations of southeast Montana. Additional storms will likely develop in northern Wyoming, closer to the mid-level speed max. RAP forecast soundings near the Montana-Wyoming state line by mid to late afternoon have MLCAPE increasing to around 500 J/kg, with 0-6 km shear near 55 knots, and 0-3 km lapse rates in the 9.5 to 10 C/km range. This environment should support a threat for severe wind gusts within the stronger downdrafts, with the greatest severe threat occurring in the late afternoon and early evening. ..Broyles/Wendt.. 04/12/2025
