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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Thursday, December 1st 2016
Created: Dec 1st 4:24 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'
 Show the Complete North American Avalanche Danger Scale
Alpine Air Alaska Inc
Special Announcement

There is a Motorized Closure order in effect for both the Seward and Glacier Ranger Districts beginning today, Dec 1st due to insufficient snow cover. We will monitor conditions daily. 


The Bottom Line

The avalanche danger is CONSIDERABLE. New snow and sustained winds have loaded a weak snowpack. Triggering a slab 1 - 2 feet thick is likely. Cautious routefinding and conservative decision-making will be essential. 

***Observations from the Summit Lake area on the Kenai are showing a similar snowpack. Weekly summaries will begin tomorrow, December 2nd. 


Primary Concern

We received the lower end of forecasted snow amounts with only 5-7 inches falling across the advisory area. This might not seem significant but there are few important factors to keep in mind. First this fell on weak surface snow, second it came in with easterly winds blowing in the 20s and gusting as high as 60mph on Sunburst, third there was already soft snow available to transport and finally the temperatures were steadily rising throughout the storm so the snow will be upside down. Colder snow will be under warmer heavier snow. Then put this all on top of the surface hoar that has been the culprit in all of the avalanche activity in the last two weeks. This surface hoar sits 1-2 ft below the surface and has shown that it still has the potential to avalanche. It now has additional load on top of it and may have a more connected slab due to wind-loaded snow.  Some slopes have slid on this layer and some haven't. This combination warrants caution. It may be triggered remotely and may let you get out onto the slab before it breaks. The new snow and wind might have been the tipping point or your weight might be when you get onto the slope. 

Today it will be important to look for recent avalanches, cracking and collapsing (whumpfing). In addition look for wind deposition, wind slabs, newly formed cornices and places where you feel stiffer snow over soft snow. Keep slope angles low and pay attention to what is above and below you. Remember the buried surface hoar when you are making your slope decisions. 

Buried surface hoar picture taken November 19th. Photo: Wendy Wagner

This photo was taken yesterday, November 30th on Manitoba and the same layer is still visibly intact and still showed the potential to avalanche in stability tests. 

 


Secondary Concern

The new snow last night fell onto weak surface snow, came in with wind and with a rise in temperature.  Storm slabs may be easy to trigger even at lower elevations. Investigate whether the new snow is bonding to the old snow surfaces. Pay attention to cracking and collapsing. 


Additional Concern

Watch for glide cracks and remember to limit time under these, there have been a handful that released last week. *Several cracks have been opening in popular terrain like Tincan’s Common bowl and the SW face of Sunburst. These may be hard to see with new snow.

 


Mountain Weather

Yesterday was overcast with light snow falling during the day. In the late afternoon snowfall picked up with a period of heavy snow from 3pm-7pm. Temperatures steadily rose throughout the day going from single digits into the high 20Fs. Sustained easterly winds blew 20-30 mph with gusting into the 60s. 

Today will be mostly cloudy with snow showers. 0-3'" of new snow. East winds will be light 5-15mph and temperatures will be in the high 20Fs. Tonight the chance of snow showers continues with another 0-3" possible. Winds shift to the north and temperatures drop into the low 20s and teens. 

Tomorrow will be mostly cloudy with light north winds and temperatures in the low 20s. There is a cooling trend into the weekend and a chance for more snow early next week. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 21  .5   22
Summit Lake (1400') 20  .3  4
Alyeska Mid (1700') 22 7 .7   11

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 16  ENE   30  63
Seattle Ridge(2400')  18 ESE  17   41

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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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