Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, December 20th 2015 7:00 am by CNFAIC Staff
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger at and above Treeline is CONSIDERABLE. The storm that ended yesterday brought 15+ inches of new snow and sustained winds to Turnagain Pass. Human (skier/rider or snowmachiner) triggered avalanches are likely in steep wind loaded terrain.  The potential exists to initiate a slab avalanche 1-4' deep. Cautious route finding, safe travel protocols and conservative decision-making will be essential elements to a fun, safe day in the backcountry. 

MODERATE danger exists below 1,000' where an avalanche occurring above may run into this zone.

 Show the Complete North American Avalanche Danger Scale
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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Special Announcement

Please come join us TODAY at 11 am in the motorized lot at Turnagain Pass for aFree Avalanche Rescue Workshop!!! This event is hosted by the CNFAIC forecasters and is a great opportunity to practice beacon searches and learn strategic shoveling techniques. This workshop is open to everyone and anyone (motorized and non-motorized), novices and experts, bring your friends!

Avalanche Problem 1

The storm continued on Turnagain pass yesterday depositing an additional 8+ inches during the day. There was a period where snow was falling over an inch/per hr.  Easterly winds were strong enough to move the new snow around. There was very limited visibility and no opportunity to see if there was natural avalanche activity in the Alpine. Observers reported reactive storm slabs near treeline and shooting cracks in wind effected snow. Today the snowpack will need time to adjust after this new load. Look for signs of instability. Shooting cracks, whumpfing and recent avalanching all indicate that the snowpack is tender. Watch out for areas that have stiffer snow over soft snow and look for the patterns of wind loading. Leeward and cross loaded areas in steep terrain (35 degrees and steeper) have the most potential hazard today. Fresh cornices may break very easily and should be given a wide berth. Loose snow avalanches and soft storm slabs are also possible today in steep terrain. Watch out for terrain traps, gullies and depressions, where even a small slide can bury you very deeply. Don't let clearing skies and fresh snow lure you into making poor decisions. Practice safe travel techniques: ride/ski slopes one at a time, stop in save zones, have escape routes planned and as always carry rescue gear! 

Additional Concern

We continue to monitor the buried Surface Hoar and Near Surface Facets that sit over the Thanksgiving Rain Crust to 3000' and over stiff old snow in the Alpine. These have been non-reactive in most tests on Turnagain Pass. Yesterday we couldn't see into the upper elevation start zones to see if the new load triggered any deeper slabs (or storm slabs). We did find both grain types in our pit yesterday. This buried weak layer/bed surface combination is also a concern in the shallower Summit Lake snowpack. Signs are pointing to this becoming a non-issue but it is worth thinking about today.  The snowpack has recieved a significant load and needs time to adjust. If the snowpack fails at this depth the slab could be deep and very dangerous.

Photo by Andy Moderow: Buried Surface Hoar intact and laid over. 

Mountain Weather

Yesterday's storm brought an additional 8+ inches to Turnagain Pass, with high preciptation intensity for much of the day. The storm shut down much earlier in the Girdwood Valley and there was significantly less snow south of the Pass. Storm totals: Turnagain Pass 15-18", Girdwood Valley 10-13", Summit Lake 2-5." Winds were Easterly and blew 20-30 mph gusting in the high 40s during the height of the storm. Temperatures ranged from the upper 20Fs to mid 30Fs with rain falling at sea level to approximately 800'.

Today will be partly cloudy to mostly sunny. Temperatures will be in the 20Fs and winds will be Northerly and light. Tonight will be mostly cloudy.

Tomorrow will be cloudy with a chance for scattered snow showers as a low in the Gulf pushes moisture into Southcentral. The Jet dips south later in the week and allows colder, drier air to move into the region over the holiday.

PRECIPITATION 24-hour data (6am - 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 28  1.1  63 
Summit Lake (1400')  30  1  .1  19
Alyeska Mid (1700')  30  3  .2  39

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  22 ENE  18  35 
Seattle Ridge(2400')  22 ESE*  10*  20* 

*Seattle Ridge was only collecting wind data from 5am-4pm 12/19/15. 

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).

Winter snowmachine use open/closed status and riding conditions updates

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.

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