Avalanche Advisory

Turnagain Area Avalanche Advisory Wednesday, March 12th 2014 6:51 am by Kevin Wright ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.

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With 22+ inches of storm snow yesterday morning, in addition to 4 inches in the last 24 hours we are still adapting to the new load.  Yesterday we witnessed small avalanches break in small terrain and one larger slide remotely trigger in steep terrain (with skiers approaching from a safe area).  

Today is all about giving the snowpack time to settle, bond, and adjust.  Dangerous avalanche conditions will be found without a lot of searching.  CONSIDERABLE danger will be found both above and below treeline, on all aspects.  Today is a great day to stay on lower angle slopes and enjoy the new snow in mellow terrain.  

Show the Complete North American Avalanche Danger Scale

North American Public Avalanche Danger Scale Avalanche danger is determined by the likelihood, size and distribution of avalanches. Danger Level Travel Advice Likelihood of Avalanches Avalanche Size and Distribution 5 Extreme Avoid all avalanche terrain. Natural and human- triggered avalanches certain. Large to very large avalanches in many areas. 4 High Very dangerous avalanche conditions. Travel in avalanche terrain not recommended. Natural avalanches likely; human- triggered avalanches very likely. Large avalanches in many areas; or very large avalanches in specific areas. 3 Considerable Dangerous avalanche conditions. Careful snowpack evaluation, cautious route-finding and conservative decision-making essential. Natural avalanches possible; human- triggered avalanches likely. Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas. 2 Moderate Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern. Natural avalanches unlikely; human- triggered avalanches possible. Small avalanches in specific areas; or large avalanches in isolated areas. 1 Low Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features. Natural and human- triggered avalanches unlikely. Small avalanches in isolated areas or extreme terrain. Safe backcountry travel requires training and experience. You control your own risk by choosing where, when and how you travel.

3 Considerable Alpine / Above 2,500'

Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.

3 Considerable Treeline / 1,000'-2,500'

Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.

3 Considerable Below Treeline / Below 1,000'

Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.

Avalanche Problem 1

The storm snow that makes up our primary concern started falling on Monday.  It tapered off substantially yesterday and transitioned to rain below 1000 feet.  All told, more than 2 feet of new snow fell from this storm.  Combined with a lot of wind, we have scoured areas between heavy wind loading.  

Yesterday we were finding the storm snow would break easily on the new snow/old snow interface.  This is the old surface layer about an inch above the late February crust.  This is a very easy interface to identify, no need to pull out the shovel, just dig in with your hand to find it.  Any avalanches today are likely to break a little above that crust, taking 2 feet of storm snow or greater amounts in wind loaded areas.  Areas with now buried surface hoar may behave even worse with a persistent weak layer involved.

I'll mention that avalanche activity yesterday seemed a bit sluggish - initiation was slow and avalanches were somewhat small in size for the amount of snow we got.  This doesn't mean much in terms of travel advice...  It's still an easy call when managing today's problem.  A lot of new snow on top of a crust with sporadic buried surface hoar - requires conservative travel in the backcountry.  

Avalanche Problem 2

Below 1000 feet we did get rain at the later half of this storm.  The lower you go, the more rain we got.  This isn't a big concern, just keep in mind that lower elevations have a water saturated surface layer.

The recent storm is the big news.  Storm totals listed below.  Numbers are 48 hour snow totals.  Keep in mind that the snow is settling and temperatures increased during the storm, transitioning to rain at lower elevations.

Girdwood midway - 26"  (2.25" water equivalent)

Turnagain Pass - Center Ridge - 25" (2.2" water equivalent)

Summit Lake - 12" (1" water equivalent)

Wind blew hard during the peak of the storm, which caused visually evident scouring of ridges.  Max gusts were recorded up to 114mph at ridge tops.  That wind diminished yesterday.

Today will bring a short break in precipitation intensity.  Snow and rain showers are expected throughout the day with an inch of accumulation.  Wind is increasing through the day as another weather front approaches.  

Tonight and tomorrow will bring another storm similar to the last one.  Predicted snow totals for tonight and Thursday are 14-24 inches.  There is a high wind warning in effect 2am to 8am Thursday for Turnagain Arm and Portage.

This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area (this advisory does not apply to highways, railroads, or operating ski areas).

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Apr 22, 2018 )

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