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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Tuesday, January 21st 2014
Created: Jan 21st 6:51 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 Bottom Line

We have a CONSIDERABLE avalanche danger today both above and below treeline.

Below treeline: Rain on snow has increased overnight and the possibility exists for natural wet slab avalanches today. These have the potential to break near the ground and propagate across slopes and rollovers.

Above treeline: Heavy wet snow is falling along with strong wind. This added weight could overload weak snow near the bottom of the pack resulting in a large deep slab avalanche. Additionally, cornices are building. A cornice fall is a great backcounty bomb which has the potential to trigger a larger full-depth avalanche below.

It seems many folks are finding this rainy and windy weather a bit less than enticing, but if you do head out into the backcountry - places to head are low angle slopes, 30 degrees or less in steepness, that have nothing steeper above you. 


Primary Concern

It is another wet and windy storm day in the Girdwood and Turnagain Pass area. Light rain fell yesterday up to 2000’ and has intensified overnight. Rain will persist through the day today adding up to another .75” of water. That said, wet avalanches due to continued rain on snow will be the main concern below treeline.

We have seen very little natural avalanche activity since Friday’s heavy rain event and widespread avalanche cycle. However, there was one wet slab noted on the Southeast face of Seattle Ridge just below treeline (photo below). This avalanche is one of the smaller wet slabs we have seen lately but it does show that the pack is still adjusting to the rain on snow - this can also be seen in Fitz's video HERE from Sunday. With today’s increase in precipitation we could see a few more natural wet slabs release.

Natural wet slab avalache likely occurring Sunday or very early Monday.  (1800', SE facing, 12-18" deep x ~150' wide)


Secondary Concern

Above treeline our snowpack is getting deeper by the day. We have had up to 3’ of dense heavy snow fall since Thursday night. Yes, this is good news for the upper elevations in the long term, but for the moment it is creating a dangerous deep slab avalanche problem. The weak faceted snow near the base of the snowpack was overloaded by Friday’s rapid loading event and several large full-depth avalanches occurred. Some of these propagated across entire slopes and deposited deep debris piles. This natural activity has since settled down and stability tests show likelihood of triggering becoming harder and harder but if it does go a deep and destructive avalanche is likely. With the continued stormy weather, warm temperatures, and very little upper elevation information, the deep slab issue continues to deserve much respect.

In short - this is a highly unpredictable but highly consequential avalanche problem.


Additional Concern

In the upper elevations (above 2,500’) where it has been and will continue to snow, storm snow instabilities will be a concern. These are mainly in the form of wind slabs near the upper elevation ridgelines. The Easterly winds have been strong for over 24-hours on the ridgetops. Though wind slabs were abundant yesterday around 3,000’ they were shallow (6-8" thick), stubborn and hard to crack. However, the higher one goes in elevation the more sensitive, and larger, they should be.

Cornice growth
Cornices have been growing substantially the past several days. A cornice fall right now has the potential to trigger a large deep slab avalanche. This is one more reason to steer clear of runout zones.


Mountain Weather

Another pulse of warm, wet and windy weather is over us currently. During the past 24-hours we have seen .7” of rain at the Turnagain Pass SNOTEL (1880’). Another .75 of rain is expected today. Temperatures have been in the upper 20’sF on the ridgetops and low 40’sF at sea level. Wind has been strong with averages around 50mph and gusts to 96mph from the East.

Temperatures today are expected to be in the mid to upper 20’s on the ridgetops and low 40’s at sea level. The rain/snow line will be around 2000’ once again with .75” of rain expected below this and up to 8” of heavy snow up high. Winds will remain out of the East with averages in the 60-70mph range.

The next several days look to remain warm and stormy. Models are hinting at a possible clearing by the weekend.

 

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.


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If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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