MT-ID Border Supercells Load 80 MPH Winds, Giant Hail Threat — SevereWX

Isolated strong thunderstorms are firing up right along the Montana-Idaho border, west of Butte, as of early afternoon. The Storm Prediction Center highlights a setup ripe for supercells and multicells, fueled by moderate instability (1000-1500 J/kg MLCAPE) and 35-45 kt southwesterly shear from an upper low over southern British Columbia.

Monsoonal moisture wrapping around a mid-level ridge is adding fuel, setting the stage for damaging straight-line winds exceeding 75 mph—most probable peaks at 65-80 mph—and large hail up to 1.75 inches. Any storm that roots in could pulse into a supercell, keeping hail and gusts in play through early evening.

Coverage remains the big question mark: widely scattered at best, but SPC is eyeing trends for a possible Severe Thunderstorm Watch (40% odds) through 2100Z. This activity sits on the fringe of stronger flow, so persistence will dictate if threats expand.

Folks in western Montana and central Idaho, especially near the border, should monitor radar closely. Outdoor plans this afternoon? Keep an eye on the sky.

Preparedness Tip: Have a severe weather plan ready—secure outdoor items, seek shelter indoors away from windows if storms approach, and stay tuned to local NWS updates via NOAA Weather Radio or apps.