Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Wednesday, March 13th 2013
Created: Mar 13th 6:38 am
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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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Alyeska Resort
The Bottom Line

Clear skies, cold temperatures, and a stable snowpack are contributing to keep the avalanche danger LOW.  Large unstable cornices have produced the largest and most dangerous avalanches over the last week.  Small wind slabs may be found in isolated spots at higher elevation.  Loose snow sluffs are very minor right now, and wet sluffs are unlikely today even with sunny skies because of cold temperatures.  Today is a great time to work into steeper terrain, especially on northern aspects that do not have sun crusts.

Primary Concern

We've received a few more reports of impressive cornice falls, the exact timing of which is unknown.  Without a trigger such as a person, dog, or snowmachine weighting the top of the cornice, failure is unlikely and very difficult to predict.  Heat from the sun this afternoon does not look like a big factor today, but it is worth considering that they lose strength as the air temperature gets close to the melting point. 

Avoiding unstable cornices is the key to staying safe around them.  Try not to spend excessive time underneath them and know what is underneath you when traveling along ridges. 

Check out Wendy's writeup on the large cornice avalanche in Goldpan here.

Goldpan cornice avalanche

Secondary Concern

Wind slabs are possible in higher elevation terrain, and the surprise factor and ability to propagate across larger areas could make even shallow wind slabs dangerous in steep terrain.  We got one report yesterday from the Portage valley area of a larger but shallow wind slab, the timing is unknown.  Wind overnight briefly got strong enough to blow snow around.  This concern should remain the exception rather than the rule. 

Additional Concerns -

From what we saw yesterday, loose snow will move but I wouldn't really call it a problem.  In steep terrain our team could get the top 4 inches of snow to sluff easily, but volume was low and the moving snow stayed very manageable for a skier. 

Wet snow sluffs are possible on south facing slopes late in the day.  Again, everything we've seen qualifies as manageable, low volume, and slow moving.  We have yet to see wet sluffs propagate into larger slab avalanches. 

Mountain Weather

Today looks like another day of perfect late winter weather.  Sun is in the forecast, with increasing clouds this afternoon transitioning to snow tonight and tomorrow.  Wind is light currently and should stay minimal throughout the day.  Temperatures are relatively cold, but the sunny skies will help to make the afternoon comfortable and warm.  This morning temperatures range from the mid teens in most areas to slightly below zero in the standard cold spots such as Summit Lake and Granite creek. 

Tonight, snow is possible but the bulk of the precipitation looks to be in the daylight hours on Thursday.

Graham will issue the next advisory Thurday morning, March 14th.

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: Nov 18, 2017 )

Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to 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.

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