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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Thursday, December 27th 2012
Created: Dec 27th 6:58 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

The backcountry avalanche danger remains HIGH today.  The Turnagain pass region has seen over four feet of snow (4.3” water equivalent) accumulate since Monday on what we know is a very weak foundation of faceted snow.  Based on pit results and yesterday’s field observations the snowpack is proving very unstable right now and an avalanche triggered today in steep terrain will likely be unmanageable for a skier or snowmachiner.  Backcountry travel is not recommended today. 

ANNOUNCEMENTS

There will be intermittent closures for avalanche hazard reduction work on Thursday December 27, 2012 on the Seward Highway between mileposts 44-20 (Summit Lake, Sterling Wye, and Kenai Lake).  Motorists should expect delays of up to 45 minutes between 8:30 AM and 5:00 PM.

Updates will be posted on the 511 system.  http://511.alaska.gov/


Primary Concern

New storm snow proves to be a valid concern today after several observations this week of human triggered avalanches and some downright spooky test results from our snow pits yesterday, all from below tree line.  As we have watched our seasonal snowpack more than double in a few short days, the weak layers we’ve been talking about for the last month finally have a 2-5 foot slab sitting on top of them.  This is the piece of the avalanche puzzle that has been missing until this week!  The new slab sits on several different weak layers, any of which may fail with the weight of a person causing an avalanche that will prove unmanageable in steep terrain.  We are in a direct-action avalanche situation and triggering an avalanche should be of no surprise today based on what we know about our weak foundation and overlying storm slab.  The old mantra to stay out of the mountains for at least 24 hours during and after a storm rings loud and true this week!


Secondary Concern

Easterly winds looked to have picked up overnight with the approach of this latest low-pressure system.  Even though we have limited data from upper elevations (due to poor visibility and dangerous avalanche conditions) we can safely say that tender wind slabs are forming and most likely avalanching naturally in our core advisory area.  Human triggered avalanches will be very likely in terrain above tree line today.  AKRR and DOT crews were able to affect wind slabs with artillery above Turnagain arm yesterday.  Shots were yielding consistent results producing avalanches big enough to destroy a small building or break trees.  We can expect wind slabs to continue to build today in our upper elevations.  If these don’t avalanche naturally, only time will help to heal these slabs. 


Mountain Weather

Well the snow continues to pile up this week as the pattern change we were all hoping for did not disappoint!  Turnagain pass saw an additional 8-10” of snow yesterday, turning to a rain-snow mix at 1000’ overnight.  Winds looked to have peaked from the east in the low 80’s last night. 

Today looks to be more of the same with another 3-6” of snow expected and moderate winds from the east.  The rain/ snow line will be hovering somewhere between sea level and 1000 feet as this latest low begins to dissipate today.

Looking out toward the weekend there appears to be more unsettled weather in our future!

Total snow accumulation beginning early morning on the 24th:

Girdwood Valley – ~50” snow with 5” of water equivalent
Turnagain Pass – ~45” snow with 4.3” of water equivalent
Summit lake – ~12” snow with 1.1” water equivalent


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).

Fitz will issue the next advisory Friday morning December 28th.

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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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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