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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Saturday, February 16th 2013
Created: Feb 16th 6:12 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

Colder temperatures and calm weather are trending the snowpack toward good stability.  Some problems still exist however, illustrated by large explosive triggered avalanches at the Seward Highway yesterday.  Above treeline a MODERATE danger exists for recent storm slab resting on various weak interfaces. 

Today looks like it will be a stellar day in the backcountry.  We are still within 24 hours of the end of the last storm, meaning that the snowpack is still adjusting to that load.  Some degree of terrain management and avoidance of high consequence steep terrain is advisable. 


Primary Concern

The storm ended yesterday, and left a blanket of fresh snow across all elevations and aspects of the mountains.  This is good news for backcountry quality, but makes it difficult to identify the areas of greatest concern.  Wind during the storm was trending from the east, so westerly aspects may be harboring wind pockets and larger cornices. 

A big piece of information came in yesterday from Seward highway/AKRR crews when they triggered a large avalanche near Kern creek.  The avalanche below was larger than anything we've seen in quite some time.  This begs the question - Is it still possible for a person to trigger a larger avalanche today?  It seems unlikely, but perhaps not impossible.  We think that areas closer to Girdwood may be somewhat less stable than Turnagain Pass.  This is due to greater snowfall in the recent storm cycles, and a more prominent crust/weak layer combination that has shown it can cause big avalanches.

Other storm related issues to think about -

1.  Wind loading up high - few people have ventured above 2500 feet in the last week due to poor visibility and stormy weather.  Watch for wind slabs in steep terrain.  This is a wild card, for which we currently don't have a lot of information.

2.  Cornices - are likely to be large and unstable.  We found very small cornices to be easily triggered on Thursday.

3.  Loose sluffs - Steep terrain may have enough loose powder to entrain and pick up volume.


Secondary Concern

In Turnagain Pass, we have seen occasional pits that indicate avalanche propagation is possible on a melt/freeze crust that typically varies from 1-3 feet in depth.  This problem is not evident everywhere...  The most reactive elevation seems to be between ~1900 and ~2900 feet.  It has shown itself to be worse in Girdwood than Turnagain Pass.

The video in this link illustrates the nature of the crust problem.  It isn't easy to initiate, but when it does it may propagate into deeper layers.


Mountain Weather

The last burst of snowfall which ended yesterday was the highest daily snowfall we've had in a month at Turnagain Pass.  Over the last week the snow has been piling up, slowly but surely.  Above treeline elevation is more than a foot of new snow in the last 48 hours with closer to 3 feet in the last week.  The storm had some strong wind over the last few days, which diminished Thursday evening before the snowfall ended.  Temperatures also dropped as the storm ended, placing light density, unconsolidated snow (powder) at the surface.  Currently temperatures are in the teens at low elevations and single digits at higher elevations.

Today, mostly sunny skies are expected.  Wind is moderate currently but will become light by late morning.  Snow and wind is back in the forecast tonight, leaving a short window of good weather for today.

 


Wendy will issue the next advisory on Sunday morning 2-17.

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

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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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