Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, January 20th 2018 7:00 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

A MODERATE avalanche danger exists above 2,500' where triggering a large Deep Slab avalanche (3-8+ feet) remains possible. This is a scary avalanche problem where multiple people can ski/ride/snowmanchine on a slope before an unlucky person finds a thin spot and the whole slope releases.  Steer clear of cornices by giving them extra space, and don’t be surprised by fast moving loose surface snow.  Evaluate snow and terrain carefully.

Below 2500’, the avalanche danger is LOW where triggering a slab avalanche is unlikely due to a stout crust that has formed. LOW danger does not mean no danger, a loose snow avalanche could knock you off your feet. Be aware of runout zones in the event that someone triggers a very large avalanche in the alpine that could run into the mid elevation zone. 

For information about Summit Lake avalanche conditions click HERE.

 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

Deep Persistent Slabs

Almost Certain
Very Likely


Very Large


A high consequence, stubborn to trigger avalanche problem lurks above 3000’, where it will be easy to assume a false sense of stable conditions. A stout crust has stabilized the snowpack in the mid and lower elevations, and this crust disappears under the new snow somewhere around 3000’. In the Alpine several weak layers (buried surface hoar and facets) remain preserved deep within the snowpack, under 3-8+ feet of snow. Basically there is an invisible gray line between Treeline and the Alpine where the snowpack goes from stable to a Deep Persistent Slab problem without notice.

Several tracks may be on a slope before someone finds a trigger spot, a thinner area of the snowpack, that takes the whole slope. Because this problem is impossible to assess without x-ray vision, an element of luck will be involved if you ride/ski in big terrain without incident. You can manage this problem with your elevation by sticking to terrain below 3000’ or by choosing low-consequence terrain in the alpine. Don't forget the bigger your objective, the bigger the size of a potential avalanche. 

Keep in mind:

  • Obvious signs of instability like collapsing “whumpfing” may not be present until it’s too late
  • Be aware of people above and below you, an avalanche from above could run much further than expected
  • Remote triggering is possible from a thinner area of the snowpack
  • Snow pits and stability tests may not be representative of the slope you are evaluating


A natural avalanche on Sunburst released mid-storm, likely Tuesday (1/16), and serves as a good reminder that slopes that have already avalanched, during one of the many storms this season, should not be considered safe. This recent avalanche was 3/4 of mile wide, ran 2000’, and filled up the entire drainage of Taylor Creek.



The 1st pit was dug just above the crown on Sunburst at 3400' in a thinner area of the snowpack. The 2nd pit was a few hundred feet away in the bed surface. This is a good example of the poor structure that is buried 3-8+ deep in many places. 



Avalanche Problem 2


Almost Certain
Very Likely


Very Large


Cornices have been growing over the last week and could be easy to trigger. Give these features a lot of space and remember they can break further back from a ridge than expected.  A cornice fall also has the potential to trigger a very large avalanche on the slope below.

Additional Concern

Dry Loose

Fast moving surface snow “sluff” was observed yesterday and it could knock a skier or rider down if you’re not expecting it. You can manage this problem by slowing down and letting the snow move past you. This of course will be more problematic in steep high consiquence terrain where falling would be undesirable and is a secondary risk to the bigger problem mentioned above. 

Mountain Weather

Yesterday skies were partly cloudy and temperatures were between 15-25F. Winds were light and variable and no precipitation was recorded. 

 Today looks similar, partly cloudy temperatures ranging from mid to low teens at ridge tops to mid 20F’s near sea level. Ridge top winds are expected to remain light and variable. 

High pressure over main land Alaska is causing cold clear, and rather benign weather in Southcentral Alaska. A similar trend is expected this week and temperatures may dip into the single digits at times. 

**Seattle Ridge weather station stopped recording wind data on 1/17/18 due to rime covering the anemometer.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 20  55 
Summit Lake (1400') 18  15 
Alyeska Mid (1700') 23  43 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 18  variable  12 
Seattle Ridge(2400') 20  **n/a  **n/a  **n/a 

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, 2019 )

Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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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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