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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Thursday, January 10th 2013
Created: Jan 10th 6:14 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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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The Bottom Line

The hazard remains at CONSIDERABLE above treeline today, where large destructive avalanches are possible.  The likelihood of triggering large avalanches is on the decline, but the consequences of being caught are dire.  The hazard below treeline is MODERATE today where human triggered avalanches are still possible.  Conservative terrain choices are critical today.


Primary Concern

Deep slab avalanches continue to be our biggest concern.  The number of avalanches that are occurring is low, but the potential size and destructive force is very high.  We received another wake up call on Tuesday, as a snowmachiner remotely triggered a very large avalanche on Seattle Ridge where amazingly no one was buried or injured.  This avalanche had the potential to do a lot of damage.  This is the second such event in the last week

Clear skies yesterday gave us a chance to look around the Turnagain Pass area.  We were able to see a lot of old crowns that have filled in as well as one recent natural avalanche above Seattle Creek that caught our attention.  With forecasted weather not likely to change the overall hazard in the coming days, the potential for large destructive avalanches will remain.

Typically a person or snowmachine can affect a weak layer within a few feet of the surface.  The new slab formed over the Christmas through New Years period is 6-10 feet in many areas.  The most likely places to find a thin spot in the slab is above treeline where winds have created greater variation in slab depths.  
Weak layers formed between October and December are widespread.  It is safe to assume that almost anywhere you go in the mountains there is a weak layer somewhere below you.  This thick slab/weak layer combo is what is allowing for these large avalanches to occur. 

Traveling on lower angled slopes and avoiding large open terrain is your best bet for avoiding this unmanageable problem today.


Secondary Concern

Light to moderate winds have created small pockets of shallow new wind slab.  Light density snow resting on the surface will get blown around easily today.  The consequences of this problem increase in steep terrain and above terrain traps.


Mountain Weather

In the past 24 hours temps have remained in the 20s F, winds have been light to moderate averaging in the teens/twenties out of the E and SE with gusts to 38mph.  Light snow has begun to fall on Turnagain Pass and in the Girdwood Valley this morning.

In the mountains today we should expect to see light snowfall mainly in the morning with a few inches of accumulation possible.  Ridgetop winds will be out of the SE averaging 15-20mph and temps at 1000' will be in the mid 20s F.

The extended outlook calls for light precip each of the next 3 days with temps warming as a series of weak low pressure systems move through the area.

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Wendy will issue the next advisory tomorrow morning, January 11th.

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

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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.


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