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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Sunday, March 6th 2016
Created: Mar 6th 6:05 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.
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.
0 NO RATING Below Treeline / Below 1,000'
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The Bottom Line

The avalanche danger is MODERATE today in Turnagain Pass for loose snow avalanches, wind slabs, glide avalanches and cornice fall. Triggering an isolated wind slab or loose snow avalanche is possible in steep terrain following 6” of new snow that fell yesterday. Give glide cracks and cornices lots of space as they can release without warning. Evaluate the terrain for any of these issues and pay close attention to how the sun is affecting the surface snow on sunny aspects.

* If you are headed to the Summit Lake area don't forget to check the Summit Lake Summary and click HERE for recent Summit Lake observations.


Primary Concern

Welcome to spring! Even yesterday when skies were mostly covered with clouds the sun’s radiation still played a role in heating the surface of the snow. The sun’s warmth combined with already warm daytime temperatures has the potential to add stress to our avalanche concerns: wind slabs, loose snow, and cornice fall. Monitor the surface snow and plan your day accordingly.

Loose Snow: Yesterday’s new snow (5”) was not bonding well with the surface below and was easily triggered on steep test slopes. This new snow was fast moving and released easily from your ski tips. Keep this problem in mind if entering into terrain where falling could have high consequences. This avalanche problem can be managed by letting your ‘sluff’ move past you when descending. On solar aspect in the afternoon wet loose avalanches will be more difficult to manage and harder to escape. Look for natural point releases on steep slopes, near rocks, and consider avoiding aspects where the sun is heating the slope.

Wind Slabs: Yesterday this new snow arrived with moderate winds and just enough time has passed to help form cohesive slabs. It is unknown how well this new snow is bonding with the surface below, thus be on the lookout for wind slabs in the alpine. Pay attention for soft pillow shaped features, shooting cracks and ease into steeper terrain with caution.

Top 5" of loose snow was easily triggered yesterday on steep test slopes in Turnagain Pass. 

 

 


Secondary Concern

Countless glide cracks continue to threaten large areas of terrain throughout Turnagain Pass, including a mine field of cracks that cover most of the Southwest face of Cornbiscuit. There were several glide cracks that slid on Friday in the Summit Lake area and one possible new glide avalanche in the Lynx creek drainage. Glide cracks have been widening and coming out of hiding after they were covered by wind and snow during the storm cycle that ended a week ago. Limiting time spent under cracks is crucial, as they will spontaneously release without warning.

One of several many large glide cracks along Cornbiscuit's Southwest face. Photo by Kevin Dee.

 


Additional Concern

Very large cornice features can be found along most ridgetops throughout Turnagain Pass. Some have large cracks and remain precariously perched in place.  As is the general rule, give them lots of space, and limit time under them. Today warming temps and sun will be adding more stress and a snowmachine or person too close could tip the balance. 

Some cornice features may have large cracks like this one that overhangs the SW aspecet of Magnum. Photo taken on 3-2-2016


Mountain Weather

Yesterday snow and rain showers left 6” of new snow in the Turnagain Pass area, 2” happened before 7am yesterday. By late morning snow turned to rain along the highway and a brief period of sun appearted mid-day. Rain/snow line was around 1400'. Temperatures spiked in the high 30’s F at Center Ridge Weather Station and Easterly ridgetop winds were moderate become light in the afternoon and evening.

Overnight temps remained just above freezing along the road corridor (33F) and skies remained overcast. Winds were light with no new accumulation after midnight.

Today expect isolated rain and snow showers throughout the morning and afternoon becoming partly cloudy by early evening.  Temperatures are expected to reach the mid-high 30’s F by mid-day with sun being an influence with thin cloud cover.

Tomorrow a similar pattern of rain and snow showers will continue to move through Southcentral, Alaska.

Today's weather forecast for scattered showers can produce a 'greenhouse effect' where thin cloud cover can trap short wave radiation from the sun and easily heat up the surface of the snow. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  0.4  141 
Summit Lake (1400') 33  0.1  44 
Alyeska Mid (1700') 33  0.7  108 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  15  49 
Seattle Ridge(2400') 27   n/a  n/a    n/a

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

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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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