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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Wednesday, December 21st 2016
Created: Dec 21st 4:49 am
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.
 Show the Complete North American Avalanche Danger Scale
Key Bank
Special Announcement

***Carter Lake and Snug Harbor areas are now open to motorized use as of yesterday, Tuesday Dec. 20th. Please respect other closures across the Forest. The Forest Service is monitoring conditions daily and will open more areas just as soon as there is enough snow to prevent resource damage to underlying vegetation. Thanks for your patience! 

OUTSIDE AREAS: Recent snowfall has created dangerous avalanche conditions around Southcentral and Interior, Alaska. Keep this in mind if you are headed to Snug Harbor and Carter today and please send in an observation if you see any obvious signs of instability. Check out these avalanche observations from Hatcher Pass and Petersville region where recent avalanche activity was observed over the weekend.


The Bottom Line

Today the avalanche danger is MODERATE in the Alpine where trigging a slab up to 2’ thick is still possible on steep wind-loaded terrain features. Evaluate snow and terrain carefully and manage your terrain choices with safe travel protocols. At Treeline and below the avalanche danger is LOW. Remember to avoid terrain traps where an avalanche of any size could have high consequences.

If you are headed to Summit Lake check out the Saturday Summary and recent Summit observations


Primary Concern

The touchy snowpack was that was observed over the weekend has calmed down as the new snow has settled and the snowpack is showing signs that it is adjusting. However, it is still very important to remember that the 12”-14” of new snow that accumulated incrementally fell onto suspect weak layers. A widespread layer of weak faceted snow remains our primary layer of concern and was the culprit in many skier triggered avalanches over the weekend. Monday, an observation from Sunburst showed propagation potential on a layer of buried surface hoar (buried Dec.15th) which is sitting on a wind hardened bed surface along some ridgelines. Slopes that were wind loaded due to the storm snow arriving with moderate to strong Easterly ridgetop winds have the most potential to be hazardous as the slabs are deeper and stiffer.  Watch out for areas with hard over soft snow, wind pillows or drifts and be on the look out for obvious signs like cracking and whumpfing sounds. Steep unsupported slopes and areas with stiffer connected slab over the facets or buried surface hoar should be avoided. Triggering a dangerous slab avalanche is still possible with our current snowpack set-up.  

Snow pit from Monday on Sunburst showing the December 15th layer of buried surface hoar. Photo: Heather Thamm


Secondary Concern

"Sluff" may also be fast moving on steep terrain features where the snow is loose and unconsolidated.  Be aware of terrain features that could have high consequences if knocked off your feet.


Additional Concern

Expect cornices to be sensitive and easy to break off. They also could trigger a slab avalanche below. If you choose to walk a ridgeline today, give these a wide berth and be aware of people below you.

 

 

 

A small piece of cornice fall pulled out the surface snow below yesterday in Zero Bowl. 

 

 


Mountain Weather

Yesterday was partly cloudy with afternoon sunshine. Temperatures were in the high teens and low 20Fs and winds were calm. Overnight temperatures and winds were similar.

Today and tonight will be mostly cloudy with a chance of snow. Winds will be light and northerly and temperatures will be in the 20Fs during the day dropping into the low teens/single digits overnight. 

There is cooling and clearing trend for the remainder of the week with a chance for snow returning for the Holiday weekend. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 22   0  0  28
Summit Lake (1400') 10  0  0
Alyeska Mid (1700')  24  0  0  17

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  16 ENE  15 
Seattle Ridge(2400')  21  SE  3

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 )

AREA STATUS WEATHER AND RIDING CONDITIONS
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

Subscribe to the Turnagain Area Avalanche Advisory:

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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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