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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Monday, November 28th 2016
Created: Nov 28th 4:27 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
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.

Snowmachine Specific – Avalanche Awareness and Rescue at AMDS, November 30 @ 6:30 pm - 8:00 pm | FREE

Join CNFAIC forecasters at Alaska Mining and Diving Supply for a discussion on Avalanche Awareness and Rescue. Topics addressed will be: recognizing safe zones and avalanche terrain, situational awareness and obvious signs of instability, rescue gear and training, and the risks and challenges of riding in crowded areas.


The Bottom Line

The avalanche danger is MODERATE in both the alpine and at treeline on all aspects due to a widespread layer of buried surface hoar. Human triggered persistent slab avalanches 1-2 feet thick are possible today. Triggering an isolated wind slab to is also possible on steep features near ridgetops. 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 similar snowpack. Weekly summaries will begin on December 2nd.

 


Primary Concern

It is now been over 10 days since the November 16th surface hoar layer was buried and it remains reactive and our primary layer of concern. Yesterday skiers reported triggering small slides in Main Bowl (Seattle Ridge) on the buried surface hoar layer in steeper terrain (40 degrees). One skied off of the slab and the other was carried but stayed on top. It is important to remember that this widespread layer of buried surface hoar is sitting below 1-2 feet of snow and that observers keep finding this layer on all aspects and elevations throughout Turnagain Pass. Stability tests also continue to show that is slab/weak layer combination has the potential to avalanche. Up until a few days ago human triggered (including remote triggered) avalanches were happening daily with a couple dozen avalanches reported over a 7-day period. These avalanches have been small to medium in size; just large enough to bury a person or seriously injure you in a ride. Larger and/or steeper, more wind-loaded slopes that haven’t been ridden still have the potential to avalanche and could fracture once onto the slope. Be aware of the consequences below you and keep an eye out for recent wind loading, shooting cracks and whumphing sounds (RED FLAGS).  Practice safe travel techniques like regrouping in safe zones and only expose one person at a time in avalanche terrain. This can be challenging to practice in crowded areas, thus be extra aware of other groups who may be traveling above or below you. Don’t forget buried surface hoar is a persistent weak layer and human triggered avalanche are still possible. This layer has not gone away and should be a major factor in slope choice today.

Skier triggered slides in Main Bowl, Photo: Eric Dahl

Shovel Tilt Test showing the slab over the buried surface hoar from pit near Hippy Bowl. 


Secondary Concern

The snow that fell Saturday night was light and fluffy and will easily be transported with moderate winds. Early this morning there was a few hours where the winds picked up on Seattle Ridge gusting to 30 mph. The Sunburst weather station is down so it's hard to determine if this was the same across the Pass. There was some increase in wind speeds at road level as well. It will be important to watch for signs of recent wind loading and if the snow feels stiffer underfoot. Look for shooting cracks. Triggering a small wind slab is possible in steep leeward terrain near ridgetops. This wind loading may add stress onto the buried surface hoar layer. Pay attention to changing conditions and choose terrain carefully. 


Additional Concern

Several glide avalanches have released this week including one observed Saturday morning on the West face of Pyramid. Several glide cracks have been noted in popular terrain like Tincan’s Common bowl and the SW face of Sunburst. If you see glide cracks give these a wide berth, minimize time spent underneath, and remember these are totally unpredictable. They are not triggered by humans and are the entire snowpack releasing. In places like Tincan Common this could be over 4' of snow.

 


Mountain Weather

Yesterday was partly cloudy with light winds and temperatures in the high teens/low 20Fs. Overnight temps dropped a little into the mid teens(F). The winds were northerly and there was a minor spike in winds speeds early this morning gusting up to 30mph. 

Today will be mostly sunny and cold with temperatures in the teens(F). NW winds should be light to moderate. Overnight there is a slight chance for snow and skies will be mostly cloudy. Temperatures stay cold and winds may increase depending on the track of the low in the Northeastern Pacific. 

Tomorrow will be mostly cloudy and cold with light to moderate NW winds. There will be a window of clearing on Wedesday again and then the likelihood of snow increases into the weekend but the timing and amounts are still TBD. 

***Sunburst Weather Station has not been recording weather data since Nov. 25th. We are currently assessing and hope to get it repaired soon.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  20  0 20 
Summit Lake (1400')  22 0  0   3
Alyeska Mid (1700')  22   0  0  5

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') n/a*** n/a*** n/a*** n/a***
Seattle Ridge(2400')  16  N 31

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: May 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be 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
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