Feb 5, 2010 @ 12:00 am

February 5, 2010 Avalanche Advisory

Hello! This is Steve Karkanen at the West Central Montana Avalanche Center with backcountry avalanche information for Friday, February 5, 2010.

Thanks to Carole Johnson, a Lolo National Forest employee and Dan Frigard, an Idaho Panhandle National Forest employee, for their many weekly trips into the Saint Regis Basin and nearby areas to gather snowpack information for the avalanche advisory programs on the Lolo and Idaho Panhandle National Forests.

Current Avalanche Danger

On all slopes steeper than 35 degrees and on all aspects above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely, human triggered avalanches are possible. Below 5000 feet, the avalanche danger is LOW, natural and human triggered avalanches are unlikely.

With our current conditions, just a few minutes of direct sun on steep southeast to southwest slopes can warm the snow rapidly enough to weaken the surface snow. During periods of rapid warming or during a rain event, the avalanche danger can quickly rise to CONSIDERABLE, natural avalanches are possible and human triggered avalanches likely.

Weather and Snowpack Analysis

Nearly all the SNOTEL sites recorded .20 to .40 inches of snow water equivalent or 2-4 inches of new snow since our report on Monday. Afternoon temperatures have been in the 30’s each day and the wind has been mostly tame and not moving snow from one aspect to another. Shaded aspects are skiing well and riding conditions are very good where ever the snow is deep enough.

Snow pit profiles from one end of the Bitterroot to the other and in the Rattlesnake are showing a mostly stable condition with two buried surface hoar layers and the depth hoar we have been talking about all winter in some areas being the layers of concern.

Stability testing is showing that all these weak layers have gained strength. A layer of facets under a crust in the upper 20cm of the snowpack is the weakest feature and will need careful assessment during the next storm.

Yesterday the sun came out for a few brief moments and quickly began affecting the snow surface. Periods of warming especially with direct sun on steep southerly facing slopes can rapidly raise the avalanche danger.

Weather Forecast and Avalanche Outlook

A weak warm front will push through the area Friday with light snowfall confined mostly to the higher elevations. A weak disturbance over the weekend will keep light snow showers possible Saturday and Sunday. Expect 2 to 6 inches of snowfall in the 6000-8000 foot elevation range between today and Sunday.

Everything we see in the backcountry right now is telling us we have a mostly stable condition but that does not give us the green light to abandon safe travel preparations and procedures. It is still possible to trigger an avalanche on some terrain features. Many places are still holding weak faceted snow especially on shallow rocky slopes. Pay particular attention to wind loaded terrain even after minor snowfall amounts. Always carry and know how to use a transceiver, probe and shovel and always travel with only one person exposed to hazardous terrain.

If you get out and see avalanche activity or want to send us quick snow observations, send us a note at [email protected] or call us at 406-530-9766. 530-9SNO.


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.