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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Aleph Johnston-Bloom  
Wednesday, January 18th 2017
Created: Jan 18th 4:27 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
 Show the Complete North American Avalanche Danger Scale
Key Bank
Special Announcement
  • Placer area and 20 Mile are OPEN to snowmachining as of today 1.18.17. Please reference the bottom of this page for the latest snowmachine area openings on the Chugach NF. 

  • Dangerous avalanche conditions exist in Hatcher Pass. Click HERE for an advisory update from Monday by the Hatcher Pass Avalanche Center and HERE for recent snowpack observations.
  • Join CNFAIC for our final Fireside Chat on Thursday night, Jan 19th! Aleph Johnston-Bloom will discuss how the current Turnagain area snowpack has developed over the winter, understanding the different avalanche problems described in the advisory and how to use them in decision-making. - Details HERE.

The Bottom Line

There is a MODERATE avalanche danger in the Alpine where triggering a fresh wind slab on leeward terrain is possible and in protected steep areas loose snow avalanches could be fast moving and run further than expected.  At Treeline and below the avalanche danger is LOW where triggering an avalanche is unlikely. 

***Placer and 20 Mile open today and there is limited information about the snowpack in these areas. Approach terrain with a cautious mindset and be on the lookout for Red Flags like recent avalanches, shooting cracks and collapsing. Watch for active wind loading as winds increase today. Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!!

***In the Girdwood Valley where 2.5'-3’ of snow fell this weekend, twice as much as Turnagain Pass, heighten avalanche conditions exist. Triggering a persistant slab 3+ feet thick or a larger loose snow avalanche is possible in Girdwood and should warrant extra caution!!!


Primary Concern

There is an uptick in the westerly wind speeds this morning and this is supposed to continue throughout the day with gusts into the 30s at ridgelines. Since the recent snow fell over the weekend observers have been finding mostly loose soft snow that has not been acting as a slab with the exception of a shallow skier triggered soft slab on Eddies west face witnessed on Monday. As wind speeds increase it is important to remember that there is a lot of soft snow available for transport. Fresh wind slabs may form throughout the day and be sensitive to triggering. Steep, unsupported, leeward slopes will be most suspect. 

Be on the lookout for wind transporting snow and pillowed or drifted areas. Avoid places where the snow feels stiffer and more affected by winds. 

Skier triggered shallow wind slab on Eddies West Face. Witnessed on Monday 1.16.17


Secondary Concern

Yesterday small natural loose snow avalanches and skier triggered sluffing was observed. These were larger in Girdwood where there is more loose snow. Today in areas protected from the wind triggering a loose snow avalanche will be possible on steeper slopes. Fast moving “sluff” could entrain snow, run further than expected and easily knock you off your feet. Manage this problem by letting the snow move past you and choose terrain that doesn’t have high consequences if you fall. Although it is unlikely to bury a person, keep in mind that larger terrain will have more volume. Cold temperatures could increase this problem thoughout the week as the surface snow becomes even less cohesive. 

 


Additional Concern

A variety of weak layers exist with in the snowpack and vary across our region. With the exception of avalanche mitigation in Girdwood we have not been seeing avalanches breaking into old weak layers. If traveling in this part of the forecast area this is important to remember. Prior to the storm Girdwood had a shallow, weak (faceted) snowpack and now this is under 2-3 ' of snow.  Limited snowpack information for this zone exists, triggering a deeper more high consequence avalanche is still possible. Should you see recent avalanche activity, experience shooting cracks, or “whumpfing” these are obvious clues that the snowpack is unstable. 

Observers have easily been able to pick out a buried layer of surface hoar in the lower elevations below 1500’ that was buried by this last storm event. This was found to be unreactive and does not seem to pose a much of a hazard at this point but will be important to keep in mind with more snow load in the future.  

If venturing into Placer or 20 Mile today remember we have very little snowpack information about both areas. We have a variety of weak layers and if you find the right spot with enough slab overlying one triggering an avalanche is still possible. It always advised to ride slopes one at a time, have a escape route planned, watch your riding partners and avoid terrain traps like steep gullies. Ease into terrain and let us know if you see an signs of instability today. 


Mountain Weather

Yesterday was partly cloudy, cold and winds were calm.  Temperatures were around 0F, slightly colder in the valleys and slightly warmer at ridge tops.  Overnight temps were below zero and winds picked up early this morning bumping into the teens with gusts in the 20s from the W. 

Single digits temperatures will continue today. Winds are forecasted to be NW 15-25 with gusts into the 30s. Skies should be mostly clear with some scattered clouds. Tonight and tomorrow will be similar. There is a chance of snow Friday into the weekend and temperatures are forecasted to rise as the deep polar air mass retreats. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  -4  0  0 42 
Summit Lake (1400')  -8  0  0 15
Alyeska Mid (1700')  4  0  0  43

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 15 
Seattle Ridge(2400') -2 rimed   rimed  rimed

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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