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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Saturday, January 12th 2013
Created: Jan 12th 6:09 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
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.
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The Bottom Line

Persistent deep slab problems are lingering in the backcountry.  The CONSIDERABLE danger rating above treeline is for a low likelihood but very high consequence avalanche problem.  Recent avalanche activity, both natural and human triggered, gives us enough evidence to call the backcountry dangerous right now.  The danger will be increasing this weekend as a large weather system moves in this afternoon.


Primary Concern

The deep slab problem is still our primary concern in the backcountry.  Remember, besides being a deep slab, it's also a persistent weak layer.  This means the problem is not going away quickly.  The trend for a problem like this is to take a long time for stability to improve in the absence of provoking weather.  Natural avalanches will become more likely as new precipitation starts today, which also makes human triggered avalanches more likely.  The size of expected avalanches remains very large and destructive.

Recent avalanche activity in our region includes the large snowmachine triggered slide on Seattle ridge, and the similar slide in Main Bowl on Tuesday.  Explosive triggers brought down large avalanches on Wednesday with crowns 10-15 feet deep.

Yesterday in snowpit testing we found the relatively deep and heavy snowpack is still reactive on the facets at the ground interface.  Pit tests show disconcerting results with easy failure on isolation and a significant collapsing of the weak layers.  This means that although it will be difficult for a person to initiate the collapse through the deep and strong slab layer, if a collapse begins the resulting avalanche will likely propagate, pull the entire depth of the snowpack, and become very large and destructive.

Careful routefinding will be important this weekend.  Steep slopes should be avoided.

Repeat Offender avalanche 1-8-13


Secondary Concern

Recent wind above 2000 feet showed scoured ridges in some areas of Turnagain Pass.  Isolated pockets of stiffer wind slabs should be expected if you travel up the ridges above treeline. 


Mountain Weather

The last couple days have brought generally good weather to our region.  A change is coming this weekend with expected warming, rain, and snow.

We expect an increase in the avalanche danger correlated to this weather event, with the intensity expected to peak Sunday-Monday.  For today, the beginning of this storm system will move in, with a mild increase in the avalanche danger associated with the weather event by this evening.

NWS graphic

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
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.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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