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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, March 3rd 2016
Created: Mar 3rd 5:36 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'
 Show the Complete North American Avalanche Danger Scale
Anchorage Snowmobile Club
Special Announcement

 Due minimal snow coverage and signs of snow machine impact to exposed vegetation the Primrose Trail access to Lost Lake has officially closed today, March 3, 2016.  Thanks to many of you who have made an effort to stay on the trail and to educate others about the consequences of tearing up the vegetation. Until this area recieves more snow the trail will remain closed. 

 


The Bottom Line

The avalanche danger is MODERATE today in Turnagain Pass for cornice fall, lingering wind slabs, and glide avalanches. Triggering a large cornice or an old wind slab 1-2’ is possible today and will become more of a concern throughout the day as the sun adds stress to solar aspects. Glide cracks continue to open up and move and can release spontaneously 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.

*Yesterday we received word of a large natural avalanche South of Grandview along the railroad corridor. Observations over the last few weeks have identified several buried weak layers within the snowpack in the Summit Lake area. No information is known about the structure of this particular avalanche, but is something to keep in mind if venturing into Lynx Creek or the Summit Lake zone. 


Primary Concern

Cornice fall may be one of the larger hazards today with sunshine acting to weaken these already tenuous bombs. Cornices right now are LARGE and UNPREDICTABLE- some bigger than semi-trucks and some with large cracks extending their full length. Yesterday melting snow and dripping water could be seen on cornice faces during the heat of the day along Magnum Ridge. Today the sun will continue to weaken cornices making human triggered (snowmachine or skier) and natural cornice fall more likely in the afternoon. Limiting time spent under these is key and giving them extra room along ridgelines will be necessary.  Not only would it suck to trigger a cornice while on top of one, imagine what it would be like if people were also below it. Evaluate all ridgelines and slopes for potential cornice fall and be weary of existing skin tracks and up-routes. There are many areas where the “normal” route is in the line of fire.  

 

Magnum Ridge Cornice - The estabilshed skin track is directly on top of 30-40' cornice feature. 

 

Same corniced ridge on Magnum. Note the long crack observed on February 18th before a 10 day storm added more weight and stress to this cornice. Photo by Amanda Goss.


Secondary Concern

Strong winds during a 10-day storm have created layers of wind-affected snow throughout Turnagain Pass. Observations over the last several days have been showing this problem to be stabilizing, however today’s warm temperatures and direct sun could be a catalyst for a human triggered wind slab. Triggering a wind slab is still possible on slopes steeper than 35 degrees especially on slopes with unsupported terrain features. Ease into steeper terrain with caution and avoid solar aspects if you find moist surface snow or see wet loose point releases in motion. 


Additional Concern

Glide cracks are moving and coming out of hiding after they were covered by wind and snow during the storm cycle. Although it has been several days since the last glide crack we know of released and avalanched, they are still on the move. Limiting time spent under cracks is crucial, as they will mow anything down in their path if one does release.

Very large glide crack on the SW shoulder of Cornbiscuit - view from the Seward Hwy. The entire SW face of Cornbiscuit has extensive glide cracks. Click HERE for more pictures from yesterday.

 

 


Mountain Weather

Yesterday skies were clear and sunny and temperatures reached mid-high 30’s F during the warmest part of the day, around 2pm. Calm winds switched directions mid day from an Easterly direction to a Westerly direction.  Overnight skies remained clear and temperatures dropped into the teens to mid 20’s F.

Today Westerly winds are expected in increase slightly 10-15mph along ridgetops. Skies will remain sunny and day time temperatures are expected to spike mid day.

Tomorrow a pattern shift is expected with a possibility of scattered snow showers.    

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 27  140 
Summit Lake (1400') 22  42 
Alyeska Mid (1700') 28  105 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  28 NE becoming W  10 
Seattle Ridge(2400') 24  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: 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

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
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