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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   CNFAIC Staff  
Wednesday, December 24th 2014
Created: Dec 24th 5:54 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.
0 NO RATING Below Treeline / Below 1,000'
 Show the Complete North American Avalanche Danger Scale
Alpine Air Alaska Inc
Special Announcement

Holiday Haiku

Christmas Eve is here

Mountains are ready to go

Santa bring us snow


The Bottom Line

Today the danger rating above treeline is MODERATE. The likelihood of triggering a 1-3’ slab avalanche is possible above 2500’ and could have high consequences. These slabs are most likely to be triggered on steep slopes where the snowpack is thinner. Ridgetop winds are expected to increase with a possible accumulation of 3-5".  Small, isolated wind slabs up to 8" in depth on leeward slopes are also a concern for today.  Identify steep terrain, evaluate the snowpack carefully and watch for people above and below you.

The danger rating for treeline is at LOW today and human triggered avalanches below 2500’ are unlikely. It is possible for an avalanche triggered from above to run into this elevation band, therefore be aware of skiers on slopes above you and travel one at a time under steep terrain.

There is No Rating below 1000’ due to insufficient snow coverage.


Primary Concern

The primary concern today is a one-week old slab (1 – 3’ deep) sitting on a layer of buried surface hoar. Buried surface hoar has been found over the past week throughout Turnagain Pass and Summit Lake above 2000’ on all aspects. This particular combination of weak layer plus slab is known to linger for long periods of time and explains why we are still getting some moderate to hard results in our test pits when we isolate the weak layer. No new signs of obvious instability have been reported since the Sunburst avalanche that buried one skier on December 18th.  This leads us to believe that the weak layer is adjusting to its new load and the overall stability of the snowpack is gradually improving.

The weather forecast today is calling for 3-5" of new snow throughout the day with moderate winds. This new load will contribute to our primary concern by placing additional stress on the weak layer. 

It’s important to realize a MODERATE rating refers mainly to the likelihood of initiating an avalanche and does not take consequences into consideration.  If you were to find just the right trigger point to initiate an avalanche it could propagate across the entire slope, making escape difficult at best.  Because of this we are on the higher risk side of the moderate scale. 

Persistent slabs are most likely to be triggered on steep slopes in thinner areas of the snowpack.  We are advising backcountry users to be smart about terrain choices and to think about the consequences before deciding to ski a steep slope. Take the time to evaluate the terrain and avoid steep slopes with convex rollovers or shallow areas around rocks.  

 


Secondary Concern

Ridgetop winds are expected to be moderate with gusts into the mid twenties today. We have an existing 5 inches of low density snow available for transport and are expected to recieve another 3-5" throughout the day. This is just enough wind and snow to form isolated wind slabs up to 8" deep on leeward aspects.  Terrain features such as ridges, gullies and convex rollovers will be the most likely places to encounter these newly formed pockets of slab. These slabs are expected to be small and isolated, but if caught off guard could be enough to knock you off your feet.  Pay attention to the consequences below and look for obvious signs like shooting cracks, hollow sounds, or smooth pillowy looking features.   


Mountain Weather

Yesterday skies were clear; winds were calm, and temperatures were in the 20’s F.

Overnight winds remained calm, temperatures dipped into the teens, and no precipitation was recorded.

Today temperatures are expected to remain in the high 20’s F at 1,000' and 3-5” of snow is forecasted for today.  Ridgetop winds are expected to increase to 15-25 mph out of the East.

Another 3-6” of snow is expected tonight and could continue through Christmas day. Temperatures are expected to stay in the 20’s F with highs in the low 30’s F near sea level. Winds are expected to remain moderate throughout the evening. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24 0  0 29
Summit Lake (1400') 15 0  0 4
Alyeska Mid (1700') 25 0  0 21

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  21  E 5 24
Seattle Ridge(2400')  22  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: Dec 08, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedRain and snow have fallen in Turnagain Pass this week, but not enough to open for snowmachining. Continue to check back to this site for updates.
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail is expected to 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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