Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, February 28th 2016 7:00 am by Heather Thamm
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger for Alpine and Treeline (above 1000’) has increased to HIGH again due to heavy precipitation and an unstable wet snowpack. Large natural wet avalanches and glide avalanches are likely today. Travel in avalanche terrain is not recommended until the snowpack has had time to drain. Avoid slopes 30 degrees and steeper, including runout areas in the flats.

The danger is MODERATE below 1,000' where debris from an avalanche above could run in steep terrain.

Elevated caution and a conservative mindset is recomended in the the Summit Lake area where a variety of avalanche concerns exist. See Saturday's Summit Lake Summary and click HERE for recent observations.

 Show the Complete North American Avalanche Danger Scale
4 High Alpine / Above 2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
4 High Treeline / 1,000'-2,500' Travel Advice: Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Special Announcement

Our deepest condolences to family and friends of a snowmachiner killed yesterday in an avalanche in the Nelchina area. Details of the incident are limited at this time and we will keep you posted as new information becomes available. Click HERE for an article by Alaska Dispatch News and HERE for a report from KTUU.

Avalanche Problem 1

Warm temperatures and heavy rain is weaken the snowpack in the mid elevation band. In the last 24 hours 1.8” of water (rain) fell below 1600’ and today another 1” of water is expected to fall by mid-day. This amount of water in the snowpack is increasing the likelihood for large natural wet slabs and wet loose avalanches. This is the type of snow that if a human triggers a wet avalanche it can be impossible to escape from. Our observations yesterday (video below) shows how unsupportable the mid-elevation snowpack was before the additional rain overnight and today. The only way to manage this avalanche problem is by avoiding avalanche terrain all together. Stay off of slopes steeper than 30 degrees, and maintain a safe distance from all run-out zones.

Yesterday several new piles of wet debris were seen from the road along the East face of Seattle Ridge including this wet slab seen near Ingram Creek from the Seward Hwy. 


Avalanche Problem 2

Today expect strong Easterly winds and an additional 12-15" of new snow above 1900’. This is on top of a 7-day stretch of very precipitous stormy weather that has produced and estimated 12’ of snow in the alpine and several days of above freezing temperature along Turnagain Pass road (1000'). In the upper elevations natural cornice fall and wind slab activity are likely. These dry avalanches from above could easily run into the mid elevations and entrain wet snow to the valley floor.  Again this is another reason not to go into avalanche terrain today. 

Additional Concern

Rain will continue to weaken the snowpack where existing glide cracks litter the mid elevation zones. Over the last two days a handful of glide avalanches have occurred in steep terrain and it is likely more will release today. Glides threaten a lot of well-travelled terrain on both the motorized and non-motorized side of the highway. This concern is listed in the 'Additional', but is side by side with all of the above avalanche problems for today. Today is not a good day to play in the mountains. 

Recent glide release on the N side of Eddies, seen from the Seward Hwy yesterday. Click HERE to see more glide observations from the last three days.

Mountain Weather

Overnight 1.8” of water fell at Center Ridge weather station (1800’) where temperatures remained just cool enough for snow (~18”.) Easterly winds averaged in the 30’s mph with a gust to 73 mph on Sunburst. Overnight temperatures cooled briefly along Turnagain Pass (1000’) for a short period of wet snow, but temps have already increased to 34F this morning.

Today 1” of water is expected to fall in the form of rain below 1600’ and 12” of new snow in the alpine. Warm temperatures could push rain/snow line as high as 1900’. Strong NE winds 30-40mph hour are anticipated along ridgetops. Intensity is expected to lessen by late afternoon, early evening.

Tomorrow showery conditions will persist in the form of rain and snow with the first hope of a break in precipitation Monday evening. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  18  1.8  156 
Summit Lake (1400') 34  0.3  41 
Alyeska Mid (1700') 33  0.68  106 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  ENE  31  73 
Seattle Ridge(2400') 27  n/a  n/a   n/a  

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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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