March 14 Avalanche Advisory

Weekend Avalanche Advisory
Posted March 14th at 0700

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with the weekend avalanche advisory for March 14th – 16th, 2008. The avalanche danger rating expires at midnight March 14th. 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. This weeks advisory is sponsored by Backcountryfocus.com.

Weather and Snowpack Analysis

Moderate temperatures and little snow accumulation helped stabilize the weakness we described last week that involved 18”-24” of new snow on a hard snow surface. We received reports of avalanches that occurred last Friday and Saturday that failed at this level. There were no reported injuries but at least one close call in the Rattlesnake.

Warm sunny weather Sunday and Monday left a nasty melt freeze crust on all but the most sheltered North aspects. This zipper crust will be the next feature to pay attention to if we receive several inches of snow during the next storm. It failed easily on South and east aspects during our stability tests. In the Southern Bitterroot near Lost Trail Pass, last weeks snow buried surface hoar in many locations and that feature is failing cleanly about 12” deep into the snowpack. It has gained strength the past few days but remains a concern on the steeper slopes. Observers in the Lolo Pass and Lookout Pass areas reported a much stronger overall condition than a week ago but remind us that there are still slabs out there on steep or wind loaded terrain that could be triggered by a skier or snowmobile. The overall condition has improved with the warmer weather and lack of precipitation.

Today’s Avalanche Danger

Above 6000′ in the Bitterroot Mountains from Lookout Pass South to Lost Trail Pass, the Rattlesnake Mountains North of Missoula, and the Southern Swan and Mission Mountains near Seeley Lake, the avalanche danger is MODERATE on slopes steeper than 35 degrees. Natural avalanches are unlikely, human triggered avalanches are possible.

On all other slopes the avalanche danger is LOW. Natural avalanches are very unlikely, human triggered avalanches are unlikely. Low to moderate avalanche danger never means NO avalanche danger.

At this time of year the danger of wet snow avalanches may quickly increase to CONSIDERABLE when sun exposed slopes warm above the freezing point or whenever we receive rain at the higher elevations.

Weather Forecast and Avalanche Outlook

The Missoula NOAA Weather Service is forecasting scattered to occasionally widespread snow showers through the weekend period. Snowfall accumulations are not expected to be significant for the next few days. Do return to the backcountry weather forecast each afternoon for an update on weather forecasts as NOAA Missoula Weather Service updates the backcountry weather every day by 3 PM.

Cooler weather and little snowfall will keep the avalanche danger at LOW to MODERATE conditions until the next significant snowfall or warm up.

The next avalanche advisory will be posted on March 21st, 2008.

If you are seeking further backcountry travel information please contact the local Forest Service Ranger District Office in the area where you wish to recreate or call us at 406-329-3752.