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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Friday, November 25th 2016
Created: Nov 25th 5:40 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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
BP Alaska
Special Announcement

Motorized use on Turnagain Pass is closed due to insufficient snow cover.  Please see riding area status at the bottom of this page for the most up-to-date information.


The Bottom Line

The avalanche danger remains CONSIDERABLE in the alpine on all aspects due to a widespread layer of buried surface hoar. Human triggered slab avalanches 10-20” thick are likely and may release on lower angled slopes. Be extra aware of changing weather conditions and any additional stress being added to the snowpack today.   

A MODERATE avalanche danger exists at treeline where human triggered avalanches are possible on open slopes, or debris running from an avalanche above may occur. Extra caution and safe travel protocol is advised if venturing in the backcountry. Avoid travel underneath glide cracks. 

***Observations from the Summit Lake area on the Kenai are showing a similarly unstable snowpack. Weekly summaries will begin on December 2nd.

 


Primary Concern

A widespread layer of surface hoar (formed November 15th/16th) is buried below 10-20” of snow throughout Turnagain Pass on all aspects. If you’ve been reading the advisory all week, you already know that this weak-layer/slab combo has been extremely reactive. Dozens of human triggered and remote triggered avalanches have occurred since November 17th on the popular slopes of Tincan, Sunburst, and Magnum. These avalanches have been on the edge of small to medium in size; just large large enough to bury a person or seriously injure you in a ride.  

This is important to keep in mind today and throughout the weekend with more snow heading our way. Today we could see an additional 2-6 inches of new snow and more coming this weekend. The snowpack is still unstable and an additional load will only make the consequences even larger. Maintain a conservative mindset when choosing your route and keep your slope angles gentle. Be on the lookout for obvious signs of instability like blowing snow, shooting cracks and whumphing sounds. Remember larger slopes can produce bigger avalanches. With the holiday weekend ahead there could be more people heading into the backcountry. Be extra aware of other groups above and below you and only expose one person on a slope at a time.

*Yesterday was the first day out of 7 days we haven’t received any reports of human triggered slab avalanches in Turnagain Pass. With time this layer of buried surface hoar is becoming more stubborn, but this also means the slab has the potential to fracture once well onto the slope. This was exactly the case on Wednesday (November 23rd) when two skiers triggered two avalanches on a slope that had been skied multiple times on Sunburst’s Southwest face. One of the skiers reported that both slides broke above them and were “nearly impossible to escape from.”  

Sunburst Southwest face. The avalanche on the left was remotely triggered on Tuesday, November 22nd. The avalanche near the ridge occured on November 23rd after the slope had been skied several times.  


Secondary Concern

There were two glide avalanches reported on November 23rd and other glide cracks have been observed around Turnagain and Summit area. If you see a glide crack give these a wide berth, minimize time spent underneath, and remember these are totally unpredicatable. They are not triggered by humans and are the entire snowpack releasing. 

 

A glide avalanche on Sunburst SW face that released on Wednesday November 23rd. The crack on the right continues to open and widen.


Mountain Weather

Yesterday skies were clear and no precipitation occurred. A temperature inversion kept cooler air (10-15 F) and some fog in the valley floor and ridgetop temps were in the 20’s F.  Northwest ridgetop winds were moderate (15-30mph) in the morning deminishing by noon to light Northeast winds.  

Overnight Southeast ridgetop winds increased into the 20’s mph and temperatures have been on a steady rise into the 20’s F. Light snowfall started as of 6am at Turnagain Pass. 

Today 2-6 inches of new snow may fall the upper elevations. Temperatures are anticipated to remain just below freezing at 1000’ and ridgetop winds are expected to be light from the North. This is the beginning of a several storms tracking through Southcentral Alaska in the next few days. Saturday evening into Sunday expect heavier snowfall and stronger winds.

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 22   0 17 
Summit Lake (1400') 14 
Alyeska Mid (1700') 21 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19   variable  6 27 
Seattle Ridge(2400')  22 variable  11  33 

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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