January 10, 2014 Avalanche Advisory

Above 6000 feet, the avalanche danger is CONSIDERABLE on wind loaded terrain steeper than 35 degrees.  Avalanche conditions are now dangerous.  Careful snowpack evaluation, cautious route finding and conservative decision making is essential. Natural avalanches are possible, human-triggered avalanches are likely.

At all other locations and elevations the avalanche danger is MODERATE. New snow and wind has heightened avalanche conditions on some terrain features.  Natural avalanches are unlikely but human-triggered avalanches are possible.

Good morning!  This is Steve Karkanen with the West Central Montana Avalanche Center’s avalanche advisory for Friday, January 10, 2014.  The danger rating expires at midnight tonight and does not apply to operating ski areas.

Weather and Snowpack

All mountain locations have received several inches of new snow during the past 48 hours.  The Bitterroot Range has picked up the most with easily over a foot of new snow in most locations.  The Twin Lakes SNOTEL is reporting 1.8 inches of snow water equivalent (SWE) since Tuesday morning or about 18 inches of new snow. Mountain temperatures are in the 20’s this morning with westerly wind gusting into the 40’s already at 8000 feet.

Observers were finding exceptional skiing and riding conditions with the newest snow sluffing easily on steeper terrain. By the end of the day Thursday the wind was picking up and wind slab formations were touchy. Observers in the Bitterroot were able to trigger small wind slabs that were running several hundred feet down slope on north and east facing aspects (profile). The wind was moving a lot of snow by days end at all Bitterroot mountain locations including the Lolo Pass area and the Rattlesnake.

We did not receive any information from the Hoodoo Pass area.  Hoodoo SNOTEL recorded 1.5 inches SWE since Tuesday morning. There is no doubt about the wind moving snow there today as well.

The primary avalanche problem is wind slab formation on any leeward terrain. This is only going to get worse with the anticipated high winds this weekend.

A secondary problem is storm snow slab formation on all steep terrain.  Yesterday this new snow was sluffing easily and was quite manageable as it had not yet formed a slab. During the clear weather break prior to this storm, small facets formed on the snow surface and this new snow has not bonded to that surface. The current dense storm snow and wind will easily form slabs that will be difficult to escape from if you get caught.

The deeply buried facets at or near the ground continue to gain strength but we’re still able to produce clean, energetic failures with a lot of force.  You can find these facets in shallow areas and on windward terrain.

 

Weather and Avalanche Forecast

The Missoula Office of the National Weather Service has issued a winter weather advisory for snow accumulation of up to 10 inches at the mountain passes. On Saturday, the confidence is high that widespread damaging winds will develop across the northern Rockies.  Mountain top wind speeds may reach the 80mph range. Another round of mountain snow is also expected during this event.  Windy conditions and a weather pattern favorable for mountain snow  is expected to remain with us through Monday as the jet stream parks over the northern Rockies.

I expect the avalanche danger to worsen as these high winds develop.  There is a lot of new snow available for transport and with the current weather coming from the west, any new snow will be heavier or denser making it easy for dangerous slabs to form.

It looks like we’re getting some of the best snow of the winter. Unfortunately, 60-80 mph winds won’t be much fun and will complicate safe mountain travel.

Pay close attention to where the wind deposits snow. Cracking and collapsing are sure signs of instability.  Heavy new snow and high winds almost always create unstable conditions. Pick your routes wisely, never expose more than one person at a time to a slope steep enough to slide and make sure everyone has rescue equipment in good working order.

Be safe out there!  Send us a note at [email protected] or use our public observation form if you get out and see anything interesting. Your information is very helpful and may help someone come home alive.

I will issue the next regular advisory on Tuesday, January 14, 2014.