December 14, 2012 Avalanche Advisory

Mostly stable conditions and excellent skiing and riding now prevail in the mountains of west central Montana. Hello!  This is Steve Karkanen at the West Central Montana Avalanche Center with the avalanche advisory for Friday December 14, 2012.  We are rating the avalanche danger for elevations above 6000′ at MODERATE on wind loaded terrain steeper than 35 degrees and LOW everywhere else.

Weather and Snowpack Analysis

Since last Saturday most mountain locations picked up several inches of new snow with high wind redistributing much of it on Sunday and Monday.  8000′ winds Sunday were a brutal 20-30 mph with temperatures in the teens.

Although our regular observer group does not begin field work until next Thursday, we have received several good reports from a variety of locations in the Bitterroot, the southern Swans and the Rattlesnake the past few days. All indicate similar conditions with thin snow up to 6000′ and very good snow with a solid base above 6000′.  The primary avalanche problem early in the week was at the highest elevations on steep, leeward terrain where wind and storm slabs formed after the heavy snowfall and high winds last weekend.  A backcountry skier was caught in a soft slab near Point Six last Sunday.  His report is posted on our public observations page and thankfully he was not injured nor lost any gear.

Since then, wind and snow tapered off giving the most affected areas a chance to settle.  Our stability testing tells us our primary avalanche problem will be wind slabs that formed on the higher more exposed ridgelines during the high wind early in the week. It takes a lot of force to produce failure on these north and east aspects but it’s still a good idea to check individual slopes before jumping in. Based on what we see now during our tours with strong stability test results the conditions are the best we’ve seen in a while.  Last year at this time we were watching facets grow on the surface and at the base of the snowpack. This year we have a solid base layer and no facets.

This YouTube video shows what we found in the Rattlesnake yesterday.

December 13, 2012 Rattlesnake ECT

Snow Profile on Point Six Thursday:

Weather Forecast and Avalanche Outlook

The Missoula Office of the National Weather Service is forecasting 3 weather systems to move through the northern Rockies this weekend.  The first arrives Friday with minimal precipitation.  The second storm moves in Saturday night into Sunday with snow focused over the Clearwater Mountains to the west. There is increasing confidence that the third storm will carry a lot of snow and wind into the area Monday and Tuesday.  Snowfall accumulation will be widespread and gusty SW winds will develop Monday.  The airmass is expected to warm and will contain more moisture which translates into a more dense snowfall than the area experienced last week.

Temperatures in the teens and twenties are keeping the newest snow light and dry so expect snow stability conditions to worsen if this forecast comes to fruition with heavy dense snow. Dry, clear periods may produce surface hoar which may be a future problem if later buried.

Dudley Improta will issue the advisory on Friday, December 21st.