Blizzard developing in the Northwest: routes likely to be cut off

As a major Southeast snowstorm faded last night, another one started thousands of miles away in the Pacific Northwest. It will crank up in earnest this afternoon as it moves eastward toward Big Sky Country before losing steam Wednesday afternoon. Strong winds and huge amounts of snow will make it dangerous or impossible to make deliveries in parts of the Northwest and Mountain Prairie freight regions.

The low pressure system and associated cold front have already been spreading lowland rain and mountain snow from Washington state into northern Idaho. We expect more moisture from the Pacific Ocean to flow into the storm, further strengthening it. Also, the pressure gradient will tighten between the developing low pressure approaching the region and the high pressure leaving the region, creating extremely windy conditions.

The highest peaks of the Cascade Range in Washington state could receive two to three feet of snow, making travel difficult on I-90. Although snow may change to rain this afternoon in Snoqualmie Pass and other lower elevations, the rain will change back to snow tonight and freeze, leaving a layer of ice under the snow. Wind gusts at 35 mph will blow snow, reducing visibility. Blewett Pass on US-97 will also be a problem area.

The weather will be worse heading east into the Rocky Mountains. A blizzard will slam into northern Idaho and western Montana, with the worst of the storm expected in the Glacier National Park area. Up to 12 inches of snow could fall amid extremely high winds, so whiteout conditions are likely. Wind gusts could reach 80 mph in some spots, making it extremely dangerous for even a loaded semi to move any freight through the area. The routes most affected will be US-12 through Lolo Pass, US-2 through Marias Pass, US-93 through Lost Trail pass, and I-90 through Lookout Pass. Check chain laws here for the latest updates on winter driving.

It will be tough getting around the storm. Drivers will have to head south of Wyoming to avoid dangerous conditions there, too. Extremely strong crosswinds of 45 to 55 mph and gusts reaching 80 mph will make travel risky. The most dangerous conditions are expected near Bordeaux, along I-25 between Chugwater and Wheatland, as well as the Arlington and Elk Mountain areas along I-80 between Laramie and Rawlins.

Blizzard Warnings, Winter Storm Warnings, and High Wind Warnings have been issued by the National Weather Service for this storm. Updates are available on this interactive map.