Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, December 6th 2012 6:53 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

A bump in ridgetop wind today along with the possibility of an inch of snow will change our avalanche problems slightly, but not the overall danger. We continue to have a MODERATE avalanche danger above treeline for slab and loose snow avalanches. Human triggered avalanches are possible on slopes steeper than 35 degrees and most pronounced in areas with fresh wind deposited snow. The avalanche danger will remain LOW below treeline.

Watch for a rapid rise in danger this weekend as snow and wind is finally in our forecast.

 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

An increase in ridgetop wind today, into the 20-30mph range from the east, will be enough to form shallow fresh wind slabs on the lee sides of ridges and gullies. With plenty of loose existing snow, warmer temperatures and the possibility of an inch of new snow, drifts should be fairly cohesive. These will be sitting on loose, non-cohesive snow that will make them touchy. Keep an eye out today for areas where the wind is picking up and loading slopes. Stiffer supportable snow, with any cracking and collapsing, will be bulls eye clues you found a wind slab and if the slope is steep enough, could slide.

The persistent slab problem has not entirely gone away as weak snow still lurks near the ground. See observations from yesterday. With added weight of a wind slab and a person there is the possibility of a slide breaking to the ground.  In this case, the consequences are higher than with triggering a fresh wind slab. Expect any slide triggered, no matter how small, to run far.

Avalanche Problem 2

Sluffing in the weak faceted (sugar) snow is becoming quite prevalent. This video from yesterday shows just how easy it is to initiate one of these sluffs. Even though these are easy to trigger they are also easy to avoid due to their predictable nature. Know where your sluff will go (as to not be overrun from behind) and also watch that you do not hit someone below as they are running to valley bottoms.

This is a good example of how weak our snowpack is right now. The snow has lost so much cohesion that if nudged down a slope it will gain momentum, entrain more snow and run till the slope angle lessens. Once a fresh layer of snow falls on this existing surface (Saturday through Sunday) the sugar snow wil have a hard time holding any new snow to the ground and avalanche conditions will rise rapidly.

Mountain Weather

Clear skies yesterday were replaced with cloud cover overnight and increased the frigid temperatures at Portage (10ft above sea level) from -22 to +2F overnight. Temperatures at the mid elevations and on the ridgetops have increased as well are in the 15-20F range. Winds are still light blowing 5-10mph from the NE and gusting 10-15mph. Expect temperatures to rise another degree or two throughout the day and winds to increase into the teens gusting in the 20’s from the east. We are likely to see some flurries and possibly an inch of snow today.

The big news will come Saturday and Sunday when a change in the weather pattern really sets in. Models are suggesting around 4-7” of snow on Saturday in the Eastern Turnagain Arm area (.5 water equivalent) and 12-22” of snow for Saturday night and Sunday (between 1 – 2” water equivalent). Stay tuned as we get closer to the weekend.


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). 

Graham will issue the next advisory Friday morning, December 7th.

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: May 06, 2018 )

Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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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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