March 25, 2011 Avalanche Advisory

The avalanche danger is MODERATE on all wind loaded terrain steeper than 35 degrees above 6000 feet in the west central Montana mountains. Natural avalanches are unlikely and human triggered avalanches are possible.

The avalanche danger is LOW on all other terrain above and below 6000 feet in the west central Montana mountains.

Good Morning. This is Tim Laroche at the West Central Montana Avalanche Center with your backcountry avalanche advisory for Friday, March 25th, 2011.

Weather and Snowpack Analysis

Spring has certainly sprung in western Montana this past week. Mountain temperatures have reached highs in the mid 40’s and most advisory mountain locations picked up 4-6 inches of new snow since Monday and it is currently snowing lightly in some advisory locations. The winds blew from every direction and are currently blowing 10-15mph from the east and southeast. Mountain temperatures are hovering in the low 30’s this morning.

The warmer temperatures have continued to settle and strengthen the snowpack. These snow cones are a great indicator of the snowpack continuing to settle(photo). The main concern right now is recently formed wind drifts on leeward ridgelines and cross loaded gullies at upper elevations.

On our tours this week of the southern Swan mountains, central Bitterroots, and the Rattlesnakes we found mostly stable conditions with isolated pockets of wind slabs and loose snow sluffs(photo). Now that it is snowing again and winds are continuing to move snow into drifts on leeward features it is important to pay attention to these areas. Wind drifts can be found on all aspects at the higher elevations of our advisory area. The new snow from the week is capped by a thin sun or wind crust, is staying cold, and sluffing easily on steep slopes. These sluffs can be managed easily if you are not caught by surprise.

We received yet another report of large glide cracks in the southern Missions. Adam Clark sent us this photo. This one had released and avalanched recently. These features tend to form during warm periods when water can percolate to the ground usually on top of underlying rock bands. It would be very difficult to predict when one might fail. So, like cornices, keep your distance and move quickly if you need to cross a slope directly above or underneath one of these features.

Weather Forecast and Avalanche Outlook

Today a shortwave weather feature will move through the area cooling temperatures and increasing the chances of precipitation. The winds will be out of the southwest 5-10mph and we could see 3-6 inches of new snow by tonight at the upper elevations of our advisory area. The weather should remain unsettled through the weekend with periodic weak systems moving through our area.

If we receive more snow than is forecasted, I would expect the avalanche danger to increase, otherwise it should remain the same.

I will issue the last Monday advisory for this season on Monday, March 28th.

If you get out and have the time to send us some information about what you are seeing, please use our “submit an observation” link on our website or send us a quick note at [email protected] This information is invaluable to us and in turn comes back to you in the form of a better forecast.