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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Saturday, December 24th 2016
Created: Dec 24th 4:13 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
BP Alaska
Special Announcement

***Carter Lake and Snug Harbor areas are now open to motorized use as of Tuesday, December 20th. Please respect other closures across the Forest. The Forest Service is monitoring conditions daily and will open more areas just as soon as there is enough snow to prevent resource damage to underlying vegetation. Thank you for your patience!


The Bottom Line

The avalanche danger is MODERATE this morning in the Alpine due to the possibility of fresh wind slabs on leeward aspects as winds have picked up and there is snow available for transport. At Treeline and below the danger is LOW. The danger level may rise to CONSIDERABLE at all elevations as a warm, wet and windy storm impacts the advisory area today. Watch for rapidly changing conditions, have a conservative mindset and adjust travel choices appropriately. Natural avalanches may be possible as the day progresses and human triggered likely. 

Check out the Summit Lake Summary HERE


Primary Concern

Soft settled snow will easily move as winds pick up in advance of the approaching storm. Wind slabs may be tender and easily triggered in the Alpine. As the snow starts today this will only become more likely. Wind speeds are forecasted to be easterly 25-45 mph gusting to 60 mph. Look for cracking, drifting and blowing snow. Cornices may also grow and become more tender with increasing wind, new snow and rising temperatures. 

 


Secondary Concern

As the snow starts to fall today it will land on very weak surface snow and is not expected to bond well. It is important to remember there is widespread surface hoar as well as small facets on almost surfaces from road level high into the alpine. Expect new snow to act as a slab fairly quickly due to this interface. As temperatures warm throughout the storm and the wind blows this may become even more pronounced. Rain or rain/snow mix falling on the old snow may produce avalanches as well at lower elevations. Look for red flags i.e. recent avalanches, cracking and collapsing (whumpfing). Pay attention to changing conditions!

 

Rimed surface hoar over soft settled (faceting) snow on Sunburst ridge. Photo: Kevan Dee

 


Additional Concern

We have been tracking a couple of weak layers this season. Buried surface hoar from November 16th and December 15th have both produced avalanches. These layers are still buried in the snowpack in some terrain. In addition there is faceted surface snow and new surface hoar waiting to get buried. New snow load may cause avalanches that step down into old weak layers. This may not happen initially as the storm starts but should be a factor that is remembered as it progresses. We have a weak foundation/snowpack structure. Patience will be key in the next couple of days. We could see a large avalanche cycle if this storm really does it's thing. 


Mountain Weather

Yesterday was clear with some valley fog. Temperatures were inverted with single digits in the valleys and high teens at ridge tops. Winds were light. Last night the temperatures rose into the 20s and winds picked up this morning gusting into the 30s. 

Today there is a Winter Weather Advisory for the forecast area due to a warm wet storm that is forecasted to move into the region late this morning. Easterly winds will increase with gusting into the 60s and 3-7 inches of snow is expected today. Snow may be heavy at times and there is uncertainty with how warm it will be. Rain may fall below 1000'. The storm is forecasted to continue tonight into tomorrow with an additional 6-10 inches of snow overnight and 4-6" tomorrow. The brunt of the storm is forecasted to be this evening. 

...WINTER WEATHER ADVISORY REMAINS IN EFFECT FROM NOON TODAY TO
9 AM AKST SUNDAY FOR TURNAGAIN PASS AND PORTAGE VALLEY...

* LOCATION...TURNAGAIN PASS AND PORTAGE VALLEY.

* SNOW...12 TO 19 INCHES FOR TURNAGAIN PASS. 8 TO 15 INCHES FOR
  PORTAGE VALLEY.

* VISIBILITY...ONE HALF MILE OR LESS AT TIMES.

* WIND...EAST WINDS 25 TO 45 MPH WITH GUSTS TO 60 MPH.

 Snow showers will continue into early next week with a clearing and cooling trend towards the weekend. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 15   0  0 24 
Summit Lake (1400')  7  1  .1  8
Alyeska Mid (1700')  16  0  0  16

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') Under repair    Under repair  Under repair   Under repair  
Seattle Ridge(2400') 15   SE 21  27 

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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