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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Monday, January 23rd 2017
Created: Jan 23rd 4:25 am
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
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.
 Show the Complete North American Avalanche Danger Scale
Special Announcement
  • The Friends of the CNFAIC and staff of the CNFAIC would like to extend our sincere condolences to family and friends of the Anchorage woman that was a member of the Southcentral ski community who passed away in an avalanche in British Columbia on Saturday.
  • Attention! If heading to the Southern Kenai Mountains, including the Lost Lake zone, this region is out of the advisory area but has received 3-5 feet of snow from Saturday's storm that has fallen on a reported thin/weak snowpack. Expect dangerous avalanche conditions. 
  • Dangerous avalanche conditions exist in Hatcher Pass. Click HERE for the Hatcher Pass Avalanche Center advisory and HERE for recent snowpack observations.

 


The Bottom Line

There is a MODERATE avalanche danger in the mountains surrounding Turnagain Pass for a variety of avalanche concerns. First, wind slab avalanches around 1 foot thick will be possible to trigger above treeline on slopes that get loaded today and that were loaded over the past two days. Second, on the steeper terrain that has seen little wind effect, expect to trigger sluffs that could be high volume and run far. Lastly, in the lower elevations (below 2,000', such as the Placer Valley area), watch for persistent soft slab avalanches 12-18" thick that could release on a layer of buried surface hoar. Watch for changing conditions. If the approaching storm arrives earlier in the day than forecasted the danger could rise to CONSIDERABLE.

Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!! Thanks to everyone who sent in observations over the weekend!

Girdwood Valley: 10" of new snow fell yesterday adding to the 8" that fell the day before. Slabs and loose snow avalanches (sluffs) both have the potential to be larger due to more snow. 

Summit Lake: Higher snowfall amounts fell on a generally weaker snowpack. Please check out the Saturday Summit Summary HERE

 


Primary Concern

Winds are increasing this morning as the next storm approaches. A few more inches of snow are forecasted to fall during the day and there is plenty of soft snow available to transport and to form tender wind slabs in the Alpine. Heavier, wetter snow falling today may make slabs more reactive. In addition, older wind slabs that formed over the weekend may also be triggered on steep leeward slopes. There was one skier triggered slab yesterday on a South facing slope on Lipps. In this avalanche the wind slab was resting on old hard wind crust from the wind event prior to the storm. This combination has been found in steep leeward terrain the past two days. Feel for hollow feeling snow, stiffer snow over softer snow or slab sitting on hard snow and watch for cracks that shoot out from your snowmachine, skis or board. 

Skier triggered slide on Lipps 1.22.17. Photo: Mike Records


Secondary Concern

There is a significant amount of loose snow from not only Saturday's storm but the snowfall earlier in the week. Expect sluffs to be triggered on slopes approaching 40 degrees. These are likely to be high volume and run fast and far. Sluff management will be key. In Girdwood Valley these will have more volume due to additional 10" that fell yesterday. 

 


Additional Concern

A variety of persistant weak layers exist within the snowpack and vary across our region. In most cases these layers have been generally dormant. As more load is added and the slab develops they have the potential to become more reactive. In shallower parts of the area there are developed basal facets and in many locations there is a mid-pack layer of facets from December. At the lower elevations, below 2,000', a layer of buried surface hoar exists under the last two snowfall events (12-18" below the surface). Slab avalanches failing on this layer are possible where the snow on top is stiff enough to form a slab. In most locations, the snow is too loose and therefore triggering a slab in unlikely, but it seems the party on Cornbiscuit Saturday may have found one of these lower slopes that did indeed have enough of a slab on this suspected buried surface hoar. The lower terrain in Placer Valley is an area that may have a similar set up. All of these layers are important to remember if we receive a significant load in the next couple of days!!!

Surface hoar layer that was buried on January 13th. Photo from Eddies on January 17th. This layer has been found in a number of locations below 2000' in the advisory area.


Mountain Weather

Yesterday was mostly cloudy with snow showers until late afternoon. Girdwood Valley saw consistent snowfall through most of the day with 10" of low density of snow falling. Turnagain Pass only received an inch and skies cleared in the late afternoon. Winds were light and temperatures were in the teens. Overnight temperatures started to slowly rise and winds picked up early this morning.

Today skies will be cloudy and snow showers are expected with 1-5" possible. Easterly winds will be 15-25 mph gusting into the 30s. Temperatures will rise into the 20Fs. Tonight the precipitation intensity is forecasted to increase with potential for over a foot or more of snow to fall. There is still some uncertainty about what the temperatures will be and the rain/snow line as the storm continues into tomorrow. Easterly winds will also increase overnight.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 14   1 .2   46
Summit Lake (1400')  12  0  0 25
Alyeska Mid (1700')  14  10  .5 49 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 14   ENE 19 
Seattle Ridge(2400')  13 SE   15  22

 

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

Subscribe to the Turnagain Area Avalanche Advisory:

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.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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