Avalanche Warning Feb. 1, 2008

February 1 Avalanche Advisory
Posted: February 1, 2008
Weekend Avalanche Advisory
Posted February 1 at 0700

Good Morning! This is Dudley Improta with the West Central Montana Avalanche Center’s weekend avalanche advisory for February 1-3, 2008. The avalanche danger rating expires at midnight February 1. This report is based on field observations and data collected on Thursday and describes conditions seen at that time. This advisory is the sole responsibility of the Forest Service and does not apply to operating ski areas.

AVALANCHE WARNING

An Avalanche warning is in effect for the mountains of West Central Montana. Above 5000′ on all slopes steeper than 30 degrees, the avalanche danger is HIGH. Natural and human triggered avalanches are likely. In the past 24 hours, heavy dense snow has been deposited onto a weak snowpack structure in the following areas: the Bitterroot Mountains from Lost Trail Pass North to Lookout Pass, the Rattlesnake Mountains North of Missoula (including Sheep Mountain/Wisherd Ridge), and the Southern Swan and Southern Mission Mountains near Seeley Lake.

Weather and Snowpack Analysis

The last week in January brought another healthy dose of snow along with winds. Avalanches closed I-90 near Lookout Pass last Sunday and on the same day bombs from the Snow Bowl Patrol produced sizeable slab avalanches that had loaded on west aspects. The temperatures that had been warm because of inversions again returned to single digit numbers at higher elevations. These temperatures helped produce weak snow that is now buried within the snowpack.

SNOTEL sites around the region are registering 14 to 33 inches of new snow as of Thursday evening. Winds, predominately out of the Southwest, have accompanied these storms. The anemometer atop Point Six in the Rattlesnakes registered winds in the 20 to 30 mph range with gusts into the 40 mph range. Lookout Pass was closed to emergency travel only on Thursday because of blizzard conditions.
Observers reported recent natural avalanche activity, cracking in the snow surface and settling. They also noted that snow was falling at higher elevations at more than an inch an hour.

You can check out the layers we are concerned with on You Tube:

http://www.youtube.com/watch?v=LGTQ8ksKsbE

http://www.youtube.com/watch?v=n5aQvPI6tl

Today’s Avalanche Danger

Above 5000′ in all advisory area locations, the avalanche danger is HIGH on all slopes steeper than 30 degrees. Natural and human triggered avalanches are likely. Travel in avalanche terrain is not recommended. Below 5000′ the avalanche danger is MODERATE on slopes steeper than 35 degrees and LOW at all other locations.

Weather Forecast and Avalanche Outlook

Another round of significant snowfall is expected Friday as a weather disturbance moves in from the west. This system should exit the area late Friday afternoon. An unsettled weather pattern will continue through the weekend, this may produce more snow. Expect the unstable snow conditions to continue during periods of heavy snowfall and high winds.

If you want to send us an observation or report an avalanche, go to missoulaavalanche.org and click on “submit an observation”.

The next avalanche advisory will be posted on February 8, 2008.