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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Saturday, December 1st 2012
Created: Dec 1st 6:40 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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The Bottom Line

ANNOUNCEMENT

Due to inadequate snow conditions and to prevent resource damage, operating or possessing a snowmobile on or within the Seward and Glacier Ranger Districts of the Chugach National Forest is prohibited until further notice.  You can view the official Forest Order for this closure HERE.


BOTTOM LINE

The entire shallow snowpack now consists of weak faceted forms, with surface hoar on top.  Stiffer slabs are becoming harder to find, and the avalanche danger is slowly diminishing.  Continue to be wary of pockets of stiffer snow in steep terrain above treeline where moderate avalanche danger can still be found.  


Primary Concern

Pockets of unstable snow may still be present in wind loaded areas at high elevation.  Most slopes where people are skiing have weakened to the point where the entire snowpack is one big weak faceted layer.  This actually makes the backcountry safer now than it was a couple weeks ago, except that it's easier to tag rocks on the way down...  

The analogy I've come up with compares the snowpack to engineering a building.  We all know that we can construct a tall stable skyscraper that can withstand significant stresses from wind and earthquakes.  The strength of that building relies fundamentally on the strength of the foundation.  If you build a skyscraper on top of a weak foundation, failure and catastrophic collapse is likely.  If you make a smaller and lighter building, the foundation doesn't need to be as strong to support the structure above.  Our snowpack right now is a tent, without any foundation.  The tent itself is inherently weak, but collapse of that tent isn't nearly as catastrophic as a collapse of the skyscraper.  In fact, the tent will bend when stressed before it breaks and collapses.  The big problem will happen when the next snow storm (new construction) gets placed on top of the tent.  How much weight can that tent support?

Why did the snowpack turn into one big weak layer?  Check out Wendy's temperature profile graph HERE.  It's all about weeks of high temperature gradients caused by shallow snow (only 22 inches in November) and cold air temperatures.

temperature gradient


Mountain Weather

The forecasted high wind over the last couple days has not affected the Turnagain Pass region.  Clear, sunny, and cold weather will continue today and through the weekend.  A temperature inversion is still present, making higher elevations warmer than the valleys below.  Portage this morning is reading -18 degrees, while Sunburst at 3812 ft is reading 15 above.  

A pattern change is beginning to show up in the extended forecast.  A chance of snow is predicted for next Wednesday!  


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). 

Wendy will issue the next advisory Sunday morning, December 2nd.

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: Apr 11, 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: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
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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