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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Thursday, February 26th 2015
Created: Feb 26th 6:16 am
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
2 Moderate Alpine Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
1 Low Treeline Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline
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The first annual SNOWBALL is tomorrow, Friday Feb.22. A "more formal than normal" night of music, door prizes, raffle and fun is on the schedule at the Taproot. Please join the Friends of the Chugach National Forest Avalanche Information Center and Alaska Avalanche School in an effort to support local avalanche education and information! Tickets are one sale TODAY through Taproot Events Calendar Page.


The Bottom Line

Today in the Alpine the avalanche danger is MODERATE where triggering a slab 1-3’ thick is possible in steep terrain. This is a high consequence "scary MODERATE" problem that is possible in terrain with slope angles over 35°. Below 2500’ the danger is LOW, where a supportable crust has formed on the surface. 


Primary Concern

As we move away from the most recent loading event last weekend the likelihood of triggering an avalanche is on the decline. A well-documented weak layer of facets beneath a 1-3’ slab can still be found, it has not disappeared, but the stability appears to be improving with time. No new weather events have added additional stress in the last five days and the lack of obvious instability (like no recent avalanches or widespread collapsing) point towards the weak layer slowly adjusting to its load. In test pits however, we are still finding a high likelihood of propagation, and if enough force is applied in just the right spot it could initiate a high consequence avalanche. 

This can be a tricky problem to manage in our heads as we find snow conditions in the Alpine feeling very much like the dense Chugach powder we so often associate with a stable Maritime snowpack. Just because someone skied a steep slope does not mean steep slopes are safe. Careful snowpack evaluation is recomended; getting a closer look underneath the slab could help remind you that a weak layer is lurking below.

Triggering a slab will be more likely on well-connected steeper slopes (> than 35°.) Trigger points are likely to be in thinner areas of the snowpack near rocks and along convexities of steep rollover features.

Be sure to practice safe travel habits. Constantly identify safe spots, move between islands of safety one at a time, and always have an escape zone in mind.  


Additional Concern

Today daytime temperatures and expected to be in the mid to high 30’s and if cloud cover or fog roll in, this could increase the insulating affect and start breaking down the surface crust below 2500’. If you find warm temps causing you to sink into bottomless loose snow, avoid steep terrain where wet avalanches might be possible. This avalanche concern is unlikely, but is worth mentioning as our thin mid elevation snowpack battles with spring like conditions. 

The photo below was taken from the uptrack at Seattle Ridge yesterday as a dense valley fog began lifting late in the afternoon. 


Mountain Weather

Yesterday a thick valley fog burned off later in the day and winds were calm. Temperatures were in the mid 20’s F most of the day with a spike mid day in the low 30’s F at mid elevations.  

Overnight temperatures dropped into the low 20’s F. Ridgetop winds were 10 mph out of the Southwest on Seattle Ridge. No new precipitation was recorded in the last 24 hours.

Today skies will be mostly sunny at higher elevation, and patches of valley fog are likely along Turnagain arm. Temperatures will be warm, in the mid 30’s F along ridgetops, with light to moderate winds out of the Southeast. Tonight cloud cover should move in and temperatures look to remain warm throughout the evening.

Our next chance for precipitation is Friday night into Saturday as a low-pressure system tracks in our direction from the Aleutians. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 24  40 
Summit Lake (1400') 22 
Alyeska Mid (1700')  24 23 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 20  N/A  N/A  N/A 
Seattle Ridge(2400') 20  Var.  12 

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: Feb 22, 2015 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThe CNF is in a sad state of affairs this winter in terms of motorized use. A drive over Turnagain pass in late-February looks like the monsoon season of September/ October. Though unprecedented, Rangers have not given up hope yet on a snowmachine season.... Remember March 2014??? 5 feet of snow in 5 days! This is Alaska afterall!
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: Closed
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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
© 2015 Chugach National Forest Avalanche Information Center. All rights reserved.
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