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Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, December 14th 2013 6:45 am by Kevin Wright
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

New storm snow falling on a slick rain crust is increasing the avalanche danger.  With only a moderate amount of snow from this storm, I expect only MODERATE avalanche danger.  However, confidence is low in this forecast until we are able to get into the field to verify the assessment.  

The interface of new snow on the ubiquitous crust is expected to provide poor bonding and low friction, meaning the new snow will not stick well and will slide off easily.  We also had sporadic surface hoar on top of the crust in some areas.  This unusual situation may make the avalanche conditions more dangerous than normal for a storm this size.

Natural and human triggered avalanches will be possible today in wind loaded areas, but are expected to be small in size and low volume.


 Show the Complete North American Avalanche Danger Scale
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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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Avalanche Problem 1

Given a relatively small amount of snow from this storm, I don't think storm slabs will be widespread without a wind loading component.  Areas with deeper deposition due to wind - higher elevation, near ridgetops - will be the primary avalanche concern.  

Sunburst weather station recorded a gust to 43 mph this morning.  The light weight, low density snow will be easily and quickly moved around by wind.  


Avalanche Problem 2

Areas unaffected by wind may have a tendency to form loose snow avalanches.  I expect any sluffs to be low volume and low force due to the cold, light density nature of this storm.

 


Mountain Weather

Yesterday the snowfall started in the morning.  Temperatures have risen a little bit, but remain well below freezing in all locations.  Ridgetop wind has also been increasing since yesterday, with gusts reaching into the 30s and 40s from the East.

Snowfall accumulation up to this point is around 6-8 inches near treeline with more expected up higher.  Water content is low from the cold temperatures - this is light density powder.  

Today's forecasted weather is continued snow showers, with less precipitation intensity than we had overnight.  A second round of snow will commence later this afternoon into the evening.  The storm is expected to taper off by late Sunday morning.  When it's all said and done, storm totals may reach more than a foot of snow in some places.  

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 06, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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.


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