Heavy rain falling on fresh snow is causing very dangerous avalanche conditions in the Northwest Montana backcountry.

The Flathead Avalanche Center on Tuesday extended its avalanche warning for another day as a warm atmospheric river affects the Northern Rockies. The avalanche danger on Tuesday was rated as high, and may remain at that level through Friday, the center warned in its forecast.

The warning includes the Whitefish Range, Swan Range, Flathead Range and Glacier National Park. Avalanches may run long distances and into mature forests, valley floors or flat terrain. People were advised to avoid all backcountry travel, including the “side country” areas around Whitefish Mountain Resort.

Flathead Avalanche forecaster Blase Reardon put it succinctly in his Tuesday morning forecast.

“It's a dumb damn day to be wandering around the backcountry,” Reardon wrote. “Wet, windy and very dangerous. And that follows several days of wet, windy and dangerous [weather]. With more of the same on the way. It's a good day to spend time with family and friends, or tidy your garage. Maybe return that air fryer your aunt gifted you.”

Strong wind is creating dangerous wind slabs in the higher elevations. Meanwhile, up to 1.5 inches of rain has fallen in some areas.

“That rain has fallen on a snowpack that, until Christmas Eve, consisted of dry, unconsolidated snow,” Reardon wrote.

The ample moisture is causing wet and loose avalanches, including one that blocked a lane of U.S. 2 near Stanton Creek on Monday night.

Other concerns in the snowpack are a buried layer of facets and the formation of glide cracks. One glide crack was observed in Noisy Basin, a popular backcountry destination in the Swan Range.

A shift to more seasonable winter weather is expected by midweek.

According to the National Weather Service in Missoula, snow levels will fall to valley elevations by Wednesday morning. Snowfall amounts of 10 to 25 inches are possible in the mountains. Another system will bring additional snow Thursday.

THE FIRST avalanche death of the season was reported Monday in Colorado.

One backcountry snowboarder was killed near the Berthoud Pass area in Grand County north of I-70.

A group of four were caught in the slide and two were completely buried. Both of the buried riders were located with the use of avalanche transceivers.

One was found breathing, and the other was not. Resuscitation efforts were not successful and the person’s body was recovered by search and rescue teams that evening.