Mar 2, 2009 @ 12:00 am

March 2 Avalanche Advisory

Posted Monday March 2nd, 2009 at 0600.

Good morning backcountry travelers. This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for March 2nd, 2009. 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. Expect avalanche conditions to change as weather conditions change. Our advisory area includes the Bitterroot Mountains from Lost Trail Pass North to near Lookout Pass, the Rattlesnake Mountains and the Southern Swan and Mission Mountains near Seeley Lake. Avalanche information about the St. Regis Basin can be found on the Idaho Panhandle National Forest Avalanche Center website.

Weather and Snowpack Analysis

Moderate mountain temperatures and light winds since last Friday helped quickly settle the heavy snow we received last week. Temperatures at SNOTEL sites were all well above the freezing point Sunday with the Twin Lakes SNOTEL in the Southern Bitterroot reporting 55 degrees, North Fork Jocko 51 degrees and Stuart Peak at 46 degrees at 1PM. As you would expect with those high temperatures, East to South aspects were rapidly warmed which resulted in many roller balls and a few point release wet snow sluffs coming off the steeper slopes. As soon as it clouded over and cooled this process stopped but you can expect a nasty sun crust on all but the most deeply shaded aspects the next time you get out.

We received reports this weekend from the Bitterroot Mountains and the Rattlesnake all of which indicated a mostly stable condition. Stability testing in these locations was showing that the new snow was failing at the crust that formed prior to the new snow last week but only after a great deal of force was applied to an isolated column of snow. Backcountry skiers in the Southern Swan reported variable conditions with isolated whoomping and a small slab releasing on steep North and East facing slopes involving the newest storm snow.

Current Avalanche Danger

At all advisory area locations above 5000 feet, the avalanche danger is MODERATE. Natural avalanches are unlikely but human triggered avalanches are possible. Below 5000 feet, the avalanche danger is LOW where natural avalanches are very unlikely and human triggered avalanches are unlikely. You can almost always find isolated pockets where there are dangerous avalanche conditions on some terrain features.

On sun exposed slopes during the heat of the day expect wet slab avalanche danger to increase to CONSIDERABLE when temperatures climb above the freezing point. Good indicators of potential wet slab avalanche activity are roller balls and small point release loose snow avalanches originating from rocks or trees. When the snow starts feeling like its rotten, its time to move to a cooler or more shaded location.

Weather Forecast and Avalanche Outlook

A Pacific weather system remains off the Northwest coast keeping a warm moist Southwest upper level flow over Western Montana. The jet stream associated with this system will move through the area tonight increasing mountain winds and keeping snow levels at about 6000 feet. As the Pacific weather system moves East toward Oregon late Tuesday more widespread precipitation will enter Western Montana.

We’re starting to go through melt freeze cycles on the south half of the compass which will help to further strengthen the overall stability. The weather forecast is calling for a chance of moisture to enter the area this week so be watching for where and what type of moisture we receive. Any rain on the current snowpack above 5000 feet will be immediately dangerous. Also avoid steep open slopes on the warm afternoons when roller balls are coming off the hill and you’re sinking up to your boot tops in wet snow.

If you have any information you’d like to share or have questions about anything related to snow safety, please contact us at [email protected].

The next avalanche advisory will be issued Friday, March 6th, 2009.


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.