The Winter Storm Watches issued Thursday for the Idaho-Montana high country have been upgraded to Winter Storm Warnings.
National Weather Service in Missoula confirmed Friday that conditions are expected to be more severe than initially forecast — with the Anaconda Pintler Mountains now in line for 8 to 16 inches of heavy wet snow and the highest peaks of Lemhi County and the Bitterroot Range facing up to 12 inches starting Saturday evening.
Warnings Replace Watches Across All Four Zones
The upgrade affects the same four zones placed under Watch Thursday:
Montana — Bitterroot and Sapphire Mountains: Skalkaho Pass, Nez Perce Pass and backcountry above 6,500 feet. Up to 12 inches on the highest peaks. Both named passes are backcountry road crossings with no services and limited cell service.
Montana — Butte/Blackfoot Region: Georgetown Lake, the Anaconda and Pintler Mountains and surrounding backcountry. 8 to 16 inches of wet snow across the Anaconda Pintler Mountains — the highest total in the warning package and an extraordinary amount for late June. The Anaconda Pintler Wilderness peaks top out above 10,700 feet.
Idaho — Western Lemhi County: Williams Creek Summit and backcountry above 6,500 feet. Up to 12 inches on the highest peaks.
Idaho — Eastern Lemhi County: Highway 28 from Tendoy to Lone Pine, Lemhi Pass, Bannock Pass and surrounding backcountry. Up to 12 inches on the highest peaks.
All four warnings run from 6 PM Saturday through 9 AM MDT Monday.
What Changed Since Yesterday’s Watch
Two things escalated this forecast from Watch to Warning. First, the storm system’s moisture content firmed up. Second, the Anaconda Pintler forecast was essentially doubled — from 8 inches in the Watch to 8-16 inches in the Warning.
That range puts the upper end in the category of a meaningful mid-winter storm for any U.S. mountain range.
“Heavy wet snow may down trees, blocking access to backcountry roadways,” the Missoula office warned — a particular concern since summer-green trees carry far more weight when loaded with wet snow than bare-branched winter trees, making blowdowns more likely.
New Passes Named in the Warning
The upgraded bulletin adds two specific passes not called out in Thursday’s Watch: Skalkaho Pass (Montana’s Highway 38, the scenic route through the Sapphire Mountains connecting the Bitterroot Valley to the Phillipsburg area) and Nez Perce Pass (the backcountry crossing from the Bitterroot Valley into Idaho’s Magruder Corridor and the Selway-Bitterroot Wilderness). Both are popular destinations for 4WD and overlanding travelers in early summer — and both will be dangerous or impassable under 12-plus inches of wet snow.
What Weekend Backcountry Travelers Must Do
The Warning is clear: consider delaying any planned travel into the backcountry or over high passes this weekend. If travel is unavoidable, carry tire chains, booster cables, a flashlight, shovel, blankets, extra clothing, water and a first aid kit. Wet snow at these elevations can soak through summer gear rapidly, and hypothermia is a genuine threat in 30-degree conditions at 8,000 feet.
Check Idaho road conditions at 511.idaho.gov and Montana road conditions at 511.mt.gov. Monitor updates at weather.gov/mso.
