Montana Braces for Long-Duration Atmospheric River With Damaging Winds and Feet of Mountain Snow

Overview

• NWS Missoula reports greater than 90% odds that Integrated Vapor Transport reaches roughly 250 kg/m/s for 36 to 48 hours from late Wednesday into early Saturday.
• High Wind Watches cover much of central and southwestern Montana for Wednesday night through Thursday, with gusts near 70 mph on the plains and up to 90 mph along the Rocky Mountain Front.
• Winter Storm Watches span the Bitterroot and Sapphire Mountains, the West Glacier region, and the Rocky Mountain Front from Wednesday night into early Saturday, with mountain snowfall expected to reach feet and periods of blizzard-like conditions.
• Forecast guidance calls for 3 to 6 inches of liquid along the Idaho–Montana border with favored crests near 6 to 8 inches, while valley precipitation trends to rain Thursday through Saturday after an initial mix.
• A preceding cold front dropping from southern Alberta brings gusty conditions, blowing dust, and a rain-to-snow transition before the main event, with winds expected to ease into Friday though remain gusty.