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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Kevin Wright  
Sunday, January 19th 2014
Created: Jan 19th 7:00 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
 Show the Complete North American Avalanche Danger Scale
The Libby Group
The Bottom Line

A break in the stormy weather yesterday gave us a good look around at the avalanche carnage from Friday.  As expected, many natural avalanches pulled out during the intense storm.  They varied from large high elevation dry slab to low elevation wet slab.  Many of the examples we saw were breaking at deeper layers and stripping the full depth of snow to the ground.  Explosive triggers over the last 2 days were finding some disturbing results with many large full depth sympathetic avalanches.

Today will start at CONSIDERABLE for all elevations and slowly get less stable throughout the day as another wave of precipitation hits from the South.  Temperatures remain above freezing down low for the 3rd day in a row.  Wind will pick up, reaching ridgetop speeds of 59-74mph tonight.

Human triggered avalanches are LIKELY today in steep terrain.  Full depth releases are also likely if an avalanche is initiated, making the size unmanageable for people.  


Primary Concern

This storm pushed us into a deep slab problem at higher elevations.  This means that we now have average slab depths of greater than 1 meter sitting on top of a persistent weak layer.  The avalanche implications are the same as we've been seeing, but the volume and destructive force have increased.  

With deep slab concerns a backcountry traveler will probably not see obvious signs of instabilty (whumphing, shooting cracks) until the slab actually avalanches.  It is unlikely to be triggered at the deep points, but rather at the thinner edges near scoured ridges or exposed rocks.  It may propagate large distances where it then pulls the deeper pockets.  It may allow multiple tracks before somebody finds the trigger point and avalanches the entire slope.  

Deep slab is a low probability, high consequence problem.  With continued precipitation, warm temperatures, and high wind - steep terrain should be avoided.  When active weather abates the safe terrain options will get better with time.  

This photo is on Moose mountain, above Canyon creek.  


Secondary Concern

Below 2000 feet we had significant rain on snow on Friday.  We can expect more rain today, perhaps as high as 1200 feet.  The photos below show an example of the abnormal avalanche activity that can happen with rain and warm temperatures.  This is fairly low in the Tincan trees.  3 distinct pockets released sympathetically on the steeper rolls as the weak layer collapsed.  Debris from this was very dense.  

Tincan avalanche 1550 ft elevation.  200 feet high by 1000 feet wide.  2-3 feet deep.


Mountain Weather

Friday's storm deposited over 2 feet of snow at high elevations and over 3 inches of rain or snow water equivalent at some low elevations.  Saturday gave us a break in the storm, but temperatures did not drop significantly.  

Today, more rain and snow is expected.  Another pulse of moisture is approaching from the south, originating at a deep 956mb low pressure center.  Up to another inch of water is forecasted for the next 24 hours, with the bulk of that precipitation happening tonight.  Temperatures will increase throughout the day, and snow level will rise from 500 feet to 1200 feet.  Look for a southeast wind 51-74 mph, also increasing slightly as the day progresses.

Expect continued warm temperatures through the week with more rain and snow possible.  

Current satellite image.

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: Dec 08, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedRain and snow have fallen in Turnagain Pass this week, but not enough to open for snowmachining. Continue to check back to this site for updates.
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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