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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Friday, December 18th 2015
Created: Dec 18th 6:10 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.
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
Roger Hickel Contracting
Special Announcement

CNFAIC is hosting a Free Avalanche Rescue Workshop on Sunday, December 20th at Turnagain Pass. This is a great opportunity to practice beacon searches, learn strategic shoveling techniques and meet local forecasters! This workshop is open to everyone and anyone, novices and experts.


The Bottom Line

The avalanche danger is CONSIDERABLE above 2000’ where triggering a slab 2-3’ is likely in steep terrain. Cautious route-finding should be used to avoid high consequence terrain features like large open slopes and terrain traps. Remember red flag warnings (recent precipitation, wind loading, warming temperatures, and shooting cracks) were present yesterday and an incoming storm will be adding additional stress to the snowpack today. 

A MODERATE danger rating exists below treeline where an avalanche from above could run into this elevation band in channeled terrain.


Primary Concern
  • Dec.17 Storm Totals:
  • Turnagain Pass Center Ridge: 13”
  • Girdwood Midway: 5”
  • Summit Lake: 3”

Yesterday warming temperatures and sustained Northeast winds have left 1-2’ of upside down storm snow in Turnagain Pass. This snow proved tender yesterday and shooting cracks were observed above 2000’ in places where the snow felt stiffened by the wind.  No avalanche activity was reported, but visibility was poor making it difficult to see if any natural avalanche activity occurred.

Today weather conditions will deteriorate again with the arrival of yet another storm that is expected to intensify this evening. Easterly winds will start building this morning along with snow showers by early afternoon. This weather will be adding stress to an already stressed out snowpack. Triggering a slab 2+’ deep will be more likely on unsupported terrain features like steep convex rolls, gullies, and above cliffs. Poor visibility is expected today, but should you choose to travel into the upper elevations, maintain a conservative Jedi mindset. Use stability tests like hand pits or ski pole tests to feel for upside down snow; denser snow sitting on weaker snow. Most of all don’t be tempted by the Dark Side (large open slopes.) Patience you must have!

Shooting cracks observed yesterday on Tincan and a 15" slab failed easily above the skin track where snow was unsupported.

 


Secondary Concern

We have been tracking several layers of weak snow formed in early December that are now buried under 3-4’ of snow. Poor visibility and dangerous avalanche conditions have made it difficult to evaluate this problem in the upper elevations where a large trigger, like a snowmachine, could find a sweet spot.  This is one of the those low likelihood/high consequence problems that is unlikely to occur naturally and is not manageable.  This is one more reason to avoid large steep slopes until the snowpack can adjust to its new load.   


Mountain Weather

Yesterday a total of 13” of new snow was recorded at the Turnagain Pass Center Ridge weather station. Sustained moderate winds from the Northeast became light yesterday, but not until most of the snow had already fallen. Temperatures warmed to above freezing, and rain/snow line reached 1200’ by mid afternoon.

Overnight no new precipitation was recorded, winds remained light, and temperatures cooled just below freezing (32F) at sea level.

Today Easterly winds are expected to start building this morning with the arrival of more snow. Snow showers will intensify by this evening and could bring another 1’ of new snow by tomorrow. Temperatures will be hovering around 32F making it possible for rain at sea level. 


*Weather station data is taken from 6am yesterday to 6am today. Yesterday's storm totals were calculated with the addition of yesterday wx station snow totals.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30F   4 0.4   49
Summit Lake (1400') 28F  0.1  17 
Alyeska Mid (1700') 31.5F  0.03  34 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 24F  NE  11  36 
Seattle Ridge(2400') 27F  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: 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.


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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