Jan 31, 2014 @ 6:44 am

Avalanche Advisory January 31, 2014

On slopes above 6000 feet that are steeper than 35 degrees the avalanche danger in the West Central Montana backcountry is CONSIDERABLE.  On all other terrain, steeper than 30 degrees the avalanche danger is MODERATE.

We have rescinded the avalanche warning associated with the recent winter storm; but there is still potential for human-triggered avalanches.

Good Morning, this is Dudley Improta with the West Central Montana avalanche advisory for January 31, 2014. This danger rating does not apply to operating ski areas and expires at midnight tonight. (Jan. 31).

 Weather and Snowpack Analysis

This morning, west and northwest mountain winds are ranging from 5 to 17mph. Mountain temperatures are in the mid-twenties to mid-teens (F). The storm that began Tuesday evening deposited 1.5 to 2 feet of snow. The area continued to pick up snow last night and it is snowing lightly this morning. The storm came in warm and then temperatures went cold; this trend helped avalanche conditions be less sensitive.

Yesterday, observers in the field were finding a weak snow surface from the recent storm. Stability tests were showing low strength and moderate energy in the new snow. (snow profile Rattlesnakes) (snow profile Lost Trail Pass).

The Snow Bowl Patrol was able to trigger 10-15 inch soft slab avalanches with explosives on southwest couloirs. Travis Craft and I were able to ski-cut this same slab, on a northeast aspect in the Rattlesnake backcountry. (Photo_ human-triggered soft slab_Rattlesnakes) Observers at Lost Trail and the guides at Yurtski, in the Southern Swans, noted the same storm slab. All areas reported weak surface conditions with no discernible hard slab formation. And, although outside of our advisory area, observers at Lookout Pass noted the same conditions.

The surface hoar, that formed previous to the storm, was not the consistent weak layer for the new snow to fail on.  We dug five pits in the Rattlesnakes and didn’t find it;  but, the guides at Yurtski reported they were avoiding areas where they had seen it – not a bad idea.

This existing soft slab can be triggered, and could be a problem on very steep slopes. Keep in mind there is more snow, from last night, available to slide. The soft slab is probably 18 to 22 inches this morning.

The main avalanche concern, for now, is the storm slab on steep open slopes.

Weather Forecast and Avalanche Outlook

Another 4 inches, or so, of snow is forecast for today.  Then, by Saturday, snowfall is predicted to taper off. Mountain clouds will hamper visibility in the high country. Winds should not be too bad (5-10mph) with high temperatures in the low twenties (F).

I would expect avalanche conditions to remain about the same through the weekend. Be aware of the potential to trigger the new snow on steep, open slopes at the higher elevations (>6000’).

 Ski and ride safe! Have a great weekend.

The next avalanche advisory will be issued February 4.

We always appreciate any observations you might have time to send in. You can use our public observations form or just send us a quick note at [email protected].


This information is the sole responsibility of the Forest Service and does not apply to operating ski areas. The avalanche danger rating expires at midnight tonight but the information can help you make a more informed decision regarding travel in avalanche terrain for the next few days.

Our advisory area includes National Forest System lands in the Bitterroot Mountains from Lost Trail Pass north to Granite Pass, the Rattlesnake Mountains north of Missoula and the Southern Swan and Mission Mountains near Seeley Lake, MT. Avalanche information for the Lookout Pass/St. Regis Basin area is available from the Idaho Panhandle Avalanche Center.