Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Friday, February 8th 2013
Created: Feb 8th 5:50 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

6-12 inches of new snow yesterday combined with strong wind created wind slabs and lingering pockets of CONSIDERABLE danger above treeline.  The danger is on a decreasing trend throughout the day, but tender slabs will be likley in wind loaded areas at higher elevations.  Below treeline you may find occasional small and shallow pockets of wind slabs and a LOW to MODERATE danger rating. 

Primary Concern

By early afternoon yesterday we could get small soft slabs to pop easily with the influence of a skier just above treeline elevation.  If we had ventured higher we would have found larger triggerable pockets with enough mass to cause injuries or burial by the end of the day.  A couple of natural avalanches were observed farther south on the Kenai peninsula despite generally poor visibility.  The main concern today is these same wind loaded pockets which may still be triggerable by a person.  The snowfall stopped around 1000pm last night and wind has diminished significantly, allowing some time for yesterday's new snow to bond and gain strength.  

 Today there will be plenty of safe places to enjoy in the backcountry.  Below treeline and areas with moderate slope angles below 35 degrees are a good bet for safe travel.  Travel above 2500 feet will require careful consideration of wind loading patterns and possibly avoidance of wind loaded areas.  At Turnagain Pass the primary wind direction was from the east, but other weather stations showed different patterns.  Determining which slopes have wind loaded pockets will require eyes on the ground.

Secondary Concern

With some areas receiving more than an inch of new water to the snowpack in the last 48 hours, I'm going to bring back the deep slab discussion.  We have not seen a deep slab avalanche in several weeks, however it remains a low probability high consequence concern.  The problem seems to have gone dormant but a couple factors could bring it back to life. 

1.  New snow adding stress to the snowpack will make it more likely to trigger the deep weak layers until the snowpack has adjusted to that new stress. 

2.  Finding a trigger point in shallow areas of the snowpack could be the influence that initiates a collapse that propagates to deeper areas. 

This problem is still in the back of my mind and is still having a subtle influence on my travel decisions in the backcountry.  Despite a period of good behavior, the deep slab is still guilty until proven innocent.

Mountain Weather

Snowfall and wind totals from yesterday

Alyeska top -       10-12 inches   gusts to 63mph

Turnagain Pass - 6-8 inches   gusts to 78mph

Summit Lake -     4-6 inches  gusts to 33mph

Snowfall from Wednesday and Thursday was low density powder, making for good skiing.  You can still feel the hard crust at low elevations underneath the new snow, but snow quality has improved.

Today looks like a break of calm and partly sunny weather before another storm on Saturday.  Isolated snow showers are possible today.  Temperatures in the high 20s to low 30s, and little to no snow is forecasted until tonight.

For the weekend a high wind watch is in effect starting Saturday morning.  More snowfall is also expected. 

Fitz will issue the next advisory tomorrow morning, February 9th.

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: Nov 18, 2017 )

Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to 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.

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