SPC Apr 12, 2025 0600 UTC Day 1 Convective Outlook

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

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