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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Wednesday, March 18th 2015
Created: Mar 18th 6:22 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.
0 NO RATING Below Treeline / Below 1,000'
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The Bottom Line

The avalanche danger for Turnagain Pass is CONSIDERABLE both in the Alpine and at Treeline. Human triggered slab avalanches up to 2’ thick will be likely in steep terrain and remotely triggered avalanches are possible. Careful snow pack evaluation and cautious route finding are essential today.

Expect snow conditions to change throughout the day and small wind slabs 4-8” thick could be an additional concern. Today is a good day to stay on low angle terrain and avoid all steep slopes. 


Primary Concern

Up to 4 inches of new snow combined with 20-30 mph ridgetops winds from the Northeast are expected today. This will continue to make human triggered slab avalanches likely on steeper slopes.  

Two days ago a storm left 2’ of new snow blanketing all of Turnagain Pass to the roadside. This slab is sitting on a weak layer of faceted snow that exists both in the Alpine and at Treeline. Yesterday conditions were very tender and a handful of slab avalanches released naturally due to unusually warm temperatures on sun-affected aspects (East and South facing slopes.) Two separate skier triggered slabs were observed on Tincan below 2500’. One of these incidents was remotely triggered causing a large pocket 200’ wide to run about 500’ down the slope.

Today avoid all steep slopes, even small ones with terrain traps below. Remotely triggered avalanches are possible and it will be extra important to not put yourself in the run-out of a steep slope, especially if other backcountry users are in the area. Obvious signs of instability like collapsing and recent avalanche activity will be additional reminders today to keep it mellow! 

Yesterday was a classic example of why CONSIDERABLE is the most dangerous rating for humans. 2’ of fresh powder followed by a sunny warm day and multiple parties pushing slope angles into steeper terrain. The photo below is of a remotely triggered slab avalanche on a WSW aspect of Tincan. Luckily no one was caught or injured.

 

 

 


Secondary Concern

Fresh Windslabs

Ridgetops winds from the Northeast are expected to be moderate 20-35 mph throughout the day. Windslabs 4-8” are possible on leeward aspects of terrain features. These wind slabs are an additional reason to stay off of steeper terrain while small bursts of precipiation and wind move through Southcentral Alaska over the next two days. 


Mountain Weather

Yesterday skies became clear and temperatures were in the mid 40’s F at lower elevations. At ridgetops temps stayed cooler, mid 20’s F and winds were light 10-20 mph from the ENE.  No new precipitation was recorded.

Overnight cloud cover kept temperatures on the warmer side, above freezing at lower elevations. Ridgetops remained in the mid 20’s F. Winds picked up along ridgetops and Sunburst was averaging mid 20’s mph from the ENE since 1am.

A low pressure centered over the Alaskan Peninsula is set up nicely to send several bursts of precipitation to Southcentral Alaska over the next two days. Expect warm temperatures, mid to high 30’s F near sea level. Rain/snow line should be near 500'. Today 4” is expected to fall at higher elevations with an additional 2-3” later in the evening. Ridgetop winds will be moderate 20-30 mph from the NE.

 *Wind data was only available at Seattle Ridge Wx station after 12am.   

PRECIPITATION 24-hour data (6am - 6am)

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 35  57 
Summit Lake (1400') 31  16 
Alyeska Mid (1700') 34  trace  .01  37 

 

RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  15  52 
Seattle Ridge(2400') 28  *N  *11  *28 

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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