Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Friday, December 28th 2012
Created: Dec 28th 6:59 am
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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The Bottom Line

The avalanche hazard remains at HIGH today, where natural avalanches are still likely and human triggered avalanches are very likely.  Below treeline the hazard is CONSIDERABLE, where the threat of natural avalanches remain and human triggered avalanches are likely.  Travel in avalanche terrain is not recommended today.

Primary Concern

The potential for skiers, riders and snowmachiners to trigger avalanches within layers of the new snow is very high today.  Terrain above treeline harbors large areas of slab, including wind slabs, that will be very sensitive to human triggers.  The steady and often rapid loading of this week has created unstable conditions in the upper layers of the snowpack.  Those of you who have ventured out into the mountains this week have witnessed this firsthand, getting machines stuck in the weak snow and enduring arduous trail breaking.  This new snow is dense and unsupported in many areas, making travel slow and challenging.  Below 1000 feet we have wet snow due to rain falling over the past 24 hours.  It all boils down to the fact that we have a lot of new snow sitting on multiple weak layers.  While we have limited info from the upper elevations, we know that the snow is very unstable, as both AKDOT & Alyeska resort have been able to trigger avalanches on a variety of aspects and elevations.  Large natural avalanches as recent as yesterday morning have been observed in the region.  The recent observations from the backcountry that we do have paint the picture of instability well.

Secondary Concern

While deep slabs are a secondary concern to storm snow/wind slabs, do not underestimate the potential destructive force of this type of problem.  Large, dense slabs that have formed over the past four days sit on a base of weak snow.  Triggering avalanches that break into these deeper layers could have dire consequences.  If caught in a deep slab avalanche, the chances of surviving are low.  I like to think of this problem as one that is unmanageable.  As such, it is important to keep terrain choices very conservative.  An avalanche triggered even in seemingly "small" terrain could have serious consequences given the large volume of snow.  While storm snow instabilities will diminish within days of the end of a storm, this deep slab problem will be with us for an extended period of time.

Mountain Weather

The Turnagain Pass area has received ~7 inches of new snow with .6 inches of water in the past 24 hrs., bringing our storm period totals to over 50 inches.  Yesterday morning winds diminished to an average of 20 mph out of the East.  Temperatures have been mild, hovering in the low 20s on ridgetops and low 30s at 1000 feet.  Rain was falling yesterday below 1,000 feet.

Today will bring lingering snow showers to the area with accumulations of up to 3 inches of snow during the day.  Temperatures will remain just below freezing at 1000 feet and winds will be out of the East and Southeast at 20-30 mph.

Snowfall and winds will increase in intensity this evening and into tomorrow.  We should expect to see this generally moist weather pattern to continue over the next several days.

Kevin will issue the next advisory Saturday morning December 29th.

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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