Western Montana Supercells Charge for 80 MPH Gusts, Large Hail — SevereWX

Isolated strong thunderstorms are firing up along the Montana-Idaho border west of Butte, fueled by monsoonal moisture and decent shear from an upper low over southern British Columbia.

SPC's Mesoscale Discussion 1651 highlights moderate instability (MLCAPE 1000-1500 J/kg) and 35-45 kt southwesterly shear supporting supercell and multicell structures through early evening. The main hazards: damaging wind gusts potentially topping 80 mph and large hail up to 1.75 inches from any persistent storms.

Coverage remains the big question mark—isolated to widely scattered for now—but SPC pegs Severe Thunderstorm Watch odds at 40% and will monitor trends closely.

This setup sits on the edge of stronger mid-level flow and a moist plume around a mid-level ridge, making for a volatile afternoon in rugged terrain.

Most probable peaks: 65-80 mph winds, 1.00-1.75 inch hail.

Check SPC's graphic for the exact outline (LAT/LON box from ~45.5N/120.6W to 47.8N/110.4W).

Preparedness: Monitor local warnings, secure outdoor items, and have a shelter plan ready if storms approach—western MT and central ID residents, stay weather-aware this evening.