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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Monday, February 13th 2017
Created: Feb 13th 4:14 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Below Treeline / Below 1,000' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
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The Bottom Line

Heavy snowfall, rain and strong winds are creating a HIGH avalanche danger at all elevations in the Turnagain Pass area, this includes Portage, Placer and Girdwood Valley. Travel is not recommended in avalanche terrain where natural avalanches are likely occurring due to rapid loading. 

 


Primary Concern

New snow and wind have combined to create very unstable slabs, 1-3’ thick.  Ridgetop winds from the East (SE to NE) picked yesterday afternoon and ramped up into the 40s and 50s mph overnight with several gusts in the 90s at Sunburst weather station. An additional 5-15" of snow is forecasted for the higher elevations today and will increase the size of these slabs. These slabs will release naturally in steep terrain and could step down into older layers in some locations. Natural avalanches could run the full length of a slope, thus it will be important to avoid being near any runout zones today. Winds and continued precipitation will make natural avalanche activity likely throughout the day. There is some uncertainty with rain/snowline today. It is already 32F at Center Ridge and raining in Girdwood. Rain may fall as high as 2000' today and the warming trend is forecasted to continue into tomorrow. Rain on snow will also increase the likelihood of natural avalanche activity at lower elevations. It is important to remember that the heavier, wetter new snow and/or rain is falling on lighter low density snow from Friday's storm and loading a layer of buried surface hoar and small facets. Avalanche activity is expected at all elevations and aspects. This set up could be a hazard even in the Tincan Trees.

This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” this problem today. 

Sunburst Weather Station this morning. Strong winds and dramatic temperature increase. Note the gusting into the 90s. 

 

 


Secondary Concern

Weak snow (facets and depth hoar) in the lower layers of the snowpack continues to be a concern in our advisory area. Today avalanches occurring in the upper layers have the potential to step down and release the entire snowpack in some places. If this does happen the volume will be large and could run long distances. 

Travel in avalanche terrain is not recommended today including being in the runout of a steep slope, like in the flats below Seattle Ridge. 

Question of the day: When will we reach the tipping point to activate these weak layers at the base of the snowpack? 


Mountain Weather

Yesterday started out with clear skies in the early morning. Clouds moved in and precipitation started early afternoon. Snowfall and winds picked up around 2 pm with over a foot of snow falling overnight. Easterly (SE-NE) winds averaged in the 40s and 50s with gusts into the 90s. Temperatures dramatically rose throughout the day starting around 0F or single digits in the morning and rising to the high 20Fs to low 30Fs by late afternoon.  

The storm continues today with another 5-15" of snow forecasted at upper elevations. Winds will continue to be easterly 20-40 mph with gusts into the 60s. Temperatures will be in the 30Fs in the valleys and the high 20s at ridgetops. The mixing of cold and warm air with the system is causing some uncertainty about the precipitation type and amount. Rain/snowline is hard to determine. There may be rain up to 2000' or higher or the cold air could stay in place and keep most of the precipitation snow. If you want to read more about it check out the NWS discussion this morning HERE

The unsettled weather continues as another a wave of moisture is supposed to impact the area tonight into tomorrow. An additional 1-2' of snow is forecasted but the temperatures and timing are still uncertain. Stay tuned and think cold thoughts... 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 25  9  1  66
Summit Lake (1400') 22  2 .4   25
Alyeska Mid (1700') 23 14  1   62

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  12 ENE   40 93 
Seattle Ridge(2400')  14  SE 25   59

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 25, 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
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