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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Wednesday, December 31st 2014
Created: Dec 31st 5:55 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
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Special Announcement


Our staff at the CNFAIC are excited to move into a new year and want to wish each of you a safe and happy ending to 2014. Happy New Years Eve!

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The CNFAIC will be hosting a FREE hands-on Avalanche Rescue Workshop this coming Sunday at Turnagain Pass!! It's only 1.5 hours, from 10:00am to 11:30am. Come join in the fun, learn some tips and practice with your gear before heading into the backcountry.


The Bottom Line

The danger rating today is CONSIDERABLE in the Alpine for wind slab avalanches up to 2-4’ thick.  These will most likely be found below ridge-tops, on leeward aspects or along gullies due to cross-loading.  Conservative route finding and careful snowpack evaluation is recommended if venturing into steep terrain.

At treeline (below 2500’) the danger is MODERATE. Small isolated wind slab avalanches are possible on wind-loaded slopes on all aspects. Avalanches are more likely to be triggered in the Alpine on steep terrain features and have the potential to run into this elevation band. Avoid being under sustained steep slopes and be aware of people above you.  

There is still very little snow below 1000'. However it is possible for debris from an avalanche above to reach our lowest elevation band, as seen in some gullies along the Seward Hwy during the storm. The danger rating today is LOW, but could return to no rating if upper elevation conditions stabilize. 


Primary Concern

During a 60-hour period, ending last night, sustained ridge top Easterly winds averaged in the mid 40’s mph with gusts as high as 88mph. We estimate snow totals to be around 12-16” in upper elevations, but unfortunately it is impossible to calculate since much of this snow has been blown away. Yesterday visibility was poor and conditions were too dangerous to access the alpine thus we don’t have much information about how the snow was loading on large steep terrain. We suspect wind slabs could be as thick as 4-5’ on leeward terrain features and below ridge tops. It is uncertain how easily a wind slab could be triggered in the Alpine today.

At mid elevations (2000 – 2800’) we did find wind slab pockets up to 2’ deep alongside large scoured slopes. We did observe these pockets to be loading low on features and well below scoured ridges. 

The storm’s predominant wind direction was from the East, but due to variable terrain features and very high mid-slope winds all aspects are suspect of wind slabs. You will most likely find isolated pockets at mid elevations and larger pockets on leeward aspects at higher elevations. Safe travel can be found on wind scoured slopes and ridges – which will be obvious, based on their rough texture and signs of old eroded ski tracks.

If you venture into the Alpine stay on scoured ridges and avoid steep terrain with hard, smooth, pillow-like features. Listen for hollow sounds and look for shooting cracks, but realize that wind slabs have a tendency to break once you are well onto the slab. It is best to avoid steep slopes that could be wind loaded until the snow has a chance to stabilize. 

Luckily, this is the type of snow condition that heals quickly as long as temperatures are cool and we don’t see any additional precipitation and wind loading. Cooler temps could also help improve the quality of the riding. Yesterday was quite variable above 2000’. 


Additional Concern

We have been tracking a buried surface hoar layer since Dec.18th when a skier triggered a large avalanche on Sunburst.  There has also been some recent concern of weak faceted snow in thinner areas of our snowpack in Girdwood and Summit Lake. As of the last 48 hours, we do not know of any recent natural avalanche activity occurring on old buried weak layers. There is just enough concern that a human could tip the balance or if a wind slab could step down to keep persistent slabs in the forefront of our minds. We suspect a slab if triggered at this layer could be as deep as 4-6’ in some upper elevation locations. It is best to avoid steep slopes today and let buried weak layers adjust to its new load.


Mountain Weather

Over the last 72 hours we have had sustained Eastern ridgetop winds in the 40’s mph with gusts into the 80’s.  Winds have decreased considerably overnight.  Precipitation has been relatively moderate with storm totals 12 -16” at higher elevations and up to 6” at the road elevation on the Northern side of Turnagain Pass. Temperatures increased from the mid 20’s F to mid 30’s F, and rain line fluctuated between 500ft to 1300ft throughout this two-day storm. 

Today, light snow accumulation, up to an inch, is expected into the early evening. Temperatures should decrease into the mid 20’s F in upper elevations and, and moderate ridgetop winds look to be shifting and coming from the South.

Clear skies are forecasted for New Years Day with temperatures in the 20’s F. Strong Northerly ridgetop winds (30 - 40mph) are expected again in Turnagain Pass on Thursday and into Friday. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33  trace   0.1 35 
Summit Lake (1400') 33  trace   0.1
Alyeska Mid (1700') 33   0.4 27 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  30  85 
Seattle Ridge(2400') 27  26  65 

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
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