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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Tuesday, December 20th 2016
Created: Dec 20th 4:49 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.
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Join CNFAIC Forecaster Aleph Johnston-Bloom for a discussion on the Turnagain Pass snowpack TONIGHT at Blue and Gold Boardshop in Anchorage from 7pm-8:30pm. Learn about how this season’s snowpack has developed and what can we expect for the holidays. 

***Carter Lake and Snug Harbor areas are open to motorized use starting today, 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

There is a CONSIDERABLE avalanche danger above treeline surrounding Turnagain Pass, Girdwood Valley and Summit Lake on the Kenai. A 1-2’ slab is sitting on weak unstable snow where human triggered avalanches are likely on steep slopes in the alpine, above 2000’. Careful snowpack evaluation, cautious route finding and conservative decision-making are essential in all areas above the trees today. 

A MODERATE avalanche danger remains in the trees and lower elevations where triggering fast moving sluff or a 12” slab is possible on steep terrain features. Remember to avoid terrain traps where an avalanche of any size could have high consiqences. 

 

 


Primary Concern

A touchy snowpack was observed over the weekend as 12”-14” of new snow fell incrementally over a four-day period in Girdwood, Turnagain Pass and Summit Lake. This new snow arrived with moderate to strong Easterly ridgetop winds, which have redistributed the snow above treeline creating varying slab depths 1-2 feet thick. Several weak layers are sitting below this slab and are suspect right now in the alpine. 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. Yesterday 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. 

Approach your day with a cautious mind-set and be skeptical of all avalanche terrain (slopes steeper than 30 degrees) in the upper elevations. Obvious signs like cracking, wumpfing sounds, or recent avalanche activity are an immediate sign that the snow is unstable. However you may not see these signs until its too late, so remember our current poor snowpack structure is considered guilty until proven innocent. If you find yourself being tempted into bigger terrain this week keep your consiquences in mind:

  • Small terrain = small avalanches = relatively manageable
  • Larger terrain = larger avalanches = unmanageable

A handful of human triggered avalanches occured mid-storm on Sunday 12-18 on Tincan and Eddies. Slab depths are now thicker (12-20") since the storm subsided and triggering this layer will take more force and could break unexpectedly once onto the slope.   

 

 

If headed to Summit Lake on the Kenai natural avalanche activity and skier triggered avalanches were observed over the weekend. Check out this observation from Tenderfoot where touchy wind slabs are sitting on a very thin and weak foundation. Photo of Butch Mountain (SW aspect) taken on Dec.17 by Mike Ausman.

 

 

 


Secondary Concern

Expect cornices to be sensitive and easy to break off. They are also likely to 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


Additional Concern

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


Mountain Weather

Snow showers yesterday brought 1-2” of new snow throughout the day. Easterly winds were light and temperatures averaged in the low to mid 20Fs. Overnight temperature dropped into the teens and winds were calm.

Today expect mostly cloudy skies and scattered snow showers. A chance of 1-3” of snow is possible. Winds are expected to be light and temperatures in the mid to low 20F’s.

A clearing trend is in the forecast for the next few days bringing cooler temperatures (teens and single digits F) and the possibility of gap winds for the Eastern Kenai Mountains.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 25  .1  29 
Summit Lake (1400') 18  .2 
Alyeska Mid (1700') 27  trace   .08 19 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 20  ENE  19 
Seattle Ridge(2400') 23  ESE   9

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: Mar 15, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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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