January 7, 2014 Avalanche Advisory

The avalanche danger is MODERATE in the mountains of west central Montana.

Above 7000 feet on slopes steeper than 35 degrees, heightened avalanche conditions exist on mainly leeward terrain and in places where faceted snow persists near the ground.  Natural avalanches are unlikely but human-triggered avalanches remain possible.

The avalanche danger is LOW at other locations and at lower elevations.  Although avalanche conditions are generally safe, unstable snow can be found on isolated terrain features.  Natural and human-triggered avalanches are unlikely.

Good morning!  This is Steve Karkanen with the West Central Montana Avalanche Center’s avalanche advisory for Tuesday, January 7, 2014.  The avalanche danger rating expires at midnight tonight and does not apply to operating ski areas.

 

Weather and Snowpack

Since Friday, SNOTEL sites picked up a few inches of new snow before skies cleared Sunday and Monday.

Friday’s high winds diminished during the past couple of days but may once again regain their influence over the mountains.  Mountain temperatures are moderating, most SNOTEL stations are in the upper 20’s this morning and a westerly wind is in the 20 mph range at 8000 feet.  Cloud cover is moving in from the west and we can expect more snow during the next few days.

We received reports from the southern Swans and Missions, the southern Bitterroot and the Rattlesnake. All these observations indicate a mostly stable snowpack with a couple of features to be aware of.

The primary avalanche problem continues to be wind slabs with persistent slabs in shallow areas a close second.

As expected, high winds moved a ton of snow around over the weekend. These high winds have been the primary sculptor of avalanche conditions recently making assessments tricky. Any aspect can be the loaded by the wind in the mountains. Terrain gets cross loaded and slopes further down the hill than you might expect can be wind loaded.

We’re also finding faceted snow near the ground in many locations but stability tests indicate continued strengthening of this persistent layer. In places where we find it, it takes a lot of force to produce failures but they do fail cleanly with energy.  This is primarily in shallow areas and on shaded aspects where the snow is less than 4 feet deep.

The only way to know for sure if the slope you want to ski or ride on is holding this faceted layer is to dig down into it.  I wouldn’t completely trust any shallow snowpack or recently wind loaded slope for a while yet.  The feeling we have is that it may take a lot to get a slope to fail, but if it does, the consequences will be severe.

 

Weather and Avalanche Forecast

The (NOAA) Missoula Weather Service Backcountry Forecast anticipates a weak weather system to move through the area later today and Wednesday. A series of organized weather systems are expected Wednesday night lasting through the weekend.  This could cause periods of moderate snow and moderate to strong west to southwest winds.

Additional snowfall with wind will increase the avalanche danger particularly on leeward terrain.

Remember that the avalanche danger rating, the avalanche advisory and weather forecast are the starting points for the information you need to help paint a complete picture of what the stability conditions are.

Pay attention to clues that give hard data about stability.  Recent avalanche activity, heavy snowfall, high winds, cracking or collapse noises and rapid warming or rain on snow all indicate unstable snow conditions.  Any of these signs rule out other evidence suggesting stability.  Nature doesn’t deceive us, we deceive ourselves.

I will issue the next advisory this Friday, January 10, 2014.