Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, December 23rd 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 is MODERATE at and above treeline in the backcountry surrounding Turnagain pass. The possibility remains for a person, or group of people, to trigger a large and dangerous slab avalanche that breaks 2-4' deep on a layer of near surface facets and/or buried surface hoar within the snowpack. This is a low probability but a high consequence situation and results in a tricky snowpack that cannot yet be trusted. The periphery areas (for example: Johnson Pass, Lynx Creek, Summit Lake and Girdwood Valley) of the forecast zone are particularly suspect due to a shallower snowpack and a more pronounced slab/weak layer set-up. Choose terrain wisely, do not put multiple snowmachines or skier/riders on or under steep slopes all at once, and watch for shooting cracks and recent avalanches.

 Below treeline the danger is LOW where there has been less snow and less wind.   

 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.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Special Announcement

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The Chugach National Forest has opened Johnson Pass trailheads (North and South) to motorized use as of yesterday.  Please see the "Riding Areas" table at the bottom of this page for current info on areas open to snowmachines.


Avalanche Problem 1

The weak snow that formed in early December sitting over the Thanksgiving Rain Crust or old hard snow is now buried under 2-4' of snow. This combination is our current cause for concern and heightened caution in the backcountry. Many large avalanches ran during the storm Saturday. The crowns were long and connected, indicative of a persistent slab problem. Smaller human and cornice triggered avalanches have also run on these buried weak layers during the past few days on Turnagain Pass and in Summit Lake. Yesterday we received reports of a snowmachine triggered avalanche up Lynx Creek (possibly remotely triggered) and shooting cracks from snowmachines up towards Johnson Pass proper. These are both signs that the snowpack is still reactive. Many people have gotten out into steep terrain with no issues but these conditions warrant continued respect. These slides may be harder to trigger but very dangerous if you happen to hit the wrong spot. Being very careful to not overload the slope is crucial. Multiple sleds or skier/riders in or under avalanche terrain should be avoided. This type of avalanche often can be triggered from shallower areas where weight can transfer to the weak layer more easily. Pay attention to slopes above you and look for signs of instability. 

Silvertip Creek: Long continuous crown at top of ridge extending out of sight from our perspective. 1-2 miles long? Photo: Joe Connelly

Additional Concern

There are multiple additional concerns to look out for today. Mostly clear skies should provide good visibility.

CORNICES: Cornices grew during the recent storm and as always travel on top of these should be avoided. They often break further back than expected and can trigger avalanches on the slopes below. Be careful not to accidently drive your snowmachine out onto them or have your ski lunch break in the wrong spot.

WIND SLABS: There was a lot of snow moved around by the wind during the storm. Stiff, pillowed, sculpted snow may indicate old wind slab that is still possible to trigger. Listen for hollow sounds and look for shooting cracks.

LOOSE SNOW:  The surface conditions have become less cohesive during the cold snap, loose snow avalanches are likely in very steep and rocky terrain. They may not be big enough to bury you but could be hazardous if they push you off of a cliff, flush you through rocky areas or into terrain traps.


Mountain Weather

Yesterday valley fog lingered throughout the day. There was mostly clear skies and sun shining above this layer. Temps were in the teens at ridge tops and single digits at valley bottoms. Winds were very light. 

Today will be a mixture of clouds and sun with the colder temperatures continuing. Winds may increase during the day blowing from the NW 10-20 mph. Tonight will be cold and clear. 

Tomorrow the weather pattern will begin to shift with clouds and warming temperatures as a low moves into the Gulf and brings our next chance for snow over the holiday weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 13   0 50 
Summit Lake (1400')  0  0 18 
Alyeska Mid (1700')  15 1.5  .06  36 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 10   10
Seattle Ridge(2400')  NNE  4  8

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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