Posted:
Jan 18, 2012 @ 1:05 pm

Avalanche Warning 1/18/12

 

On slopes that are steeper than 30 degrees there is HIGH AVALANCHE DANGER in the West Central Montana backcountry. Good afternoon, this is Dudley Improta with the West Central Montana Avalanche Center.

We are issuing an avalanche warning for January 18, 2012.

 

Weather and Snowpack Analysis

We have received plenty of snow during the last 24 hours and there is more to come. This storm started out very cold and deposited some low density fluff. The snow falling today is a bit heavier with higher density. This is a very unstable situation; warmer, denser snow sitting on top of the lighter, less dense snow. To make things even more interesting we were seeing some failures with stability testing in the upper part of the snowpack before the storm. In addition, Tim and I could get the buried surface hoar layer from December to fail in the Southern Swans over the weekend; albeit with a lot of force. It may be possible to get a very large avalanche if the new snow fails and triggers one of these pre-existing weaknesses.

This morning the Snowbowl Patrol was able to get failures in the snow with explosives and ski-cutting. Some of these avalanches had 12 to 18 inch crowns.

Moderate to high winds have been loading leeward slopes; wind-loaded slopes will be particularly dangerous.

With more snow falling right now and more predicted it is probably prudent to avoid steep slopes in the backcountry for a while. Although rare, we have had avalanche accidents in gullies and slopes below 5000 feet when we have strong winds and heavy snowfall.

Weather Forecast and Avalanche Outlook

The heaviest snowfall is predicted for the next 24 hours. The mountains could receive another 24 to 40 inches of snow by Thursday afternoon. Strong westerly winds will load the lee sides with even more snow. Given these conditions I would expect the avalanche danger to remain HIGH.

I will issue our regular advisory Friday, January 20.

Ski and ride safe!

If you want to send us quick snow observations please use our public observations form on the home page missoulaavalanche.org or write us at [email protected] with any observations or questions.

 

READ FULL ADVISORY  

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.