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Turnagain Area Avalanche Advisory
Wednesday, December 5th 2018 5:44 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger remains MODERATE above 2500’ in the Alpine. As easterly winds continue, triggering a wind slab in steep terrain will be possible. Additionally, triggering a slab avalanche 1-3’ thick, releasing on buried surface hoar, is still possible though trending to a lower likelihood.


 Show the Complete North American Avalanche Danger Scale
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'
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Avalanche Problem 1

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Sustained moderate winds from the east have been blowing for four days and will remain, to varying degrees, over the region again today. These winds have redistributed the snow and formed wind slabs and not-so-fun crusts is many areas; see Monday's field report from Turnagain HERE. Wind slabs could be found in steep terrain and could be hard enough, and stubborn enough, to allow a person on to them before popping loose. Look for stiff, pillowed snow, cracking and listen for hollow, drum-like sounds. 

Wind effect along Sunburst Ridge looking north toward Tincan Ridge.


Avalanche Problem 2

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

At the upper elevations we are keeping tabs on a thin layer of buried surface hoar sitting 1-3' below the surfaceAn observer Sunday found this layer to still be reactive in a snowpit on Sunburst right around 2500'. Monday at 3100' on Sunburst there were no results testing this layer but it was very easy to spot laid over in the snowpack. Side note, this layer was unreactive last week at 3,150' on Tincan as well. The concern is finding a slope with buried surface hoar that is still intact, upright and reactive enough that it propagates into an avalanche. At this point obvious signs of instability may not be seen but some lingering suspicion is advised even as the likelihood decreases. As always use safe travel protocol and choose terrain with consequences in mind. For example, where is the avalanche path and where would I end up if the slope slides? 

 

Pastoral Peak, looking east from Sunburst through Taylor Pass. Note the crown of a large avalanche under the rock band on Pastoral - earthquake triggered slab on Nov 30th. This avalanche likely released on the Nov. 23 buried surface hoar. 

 

Surface conditions below 1,500' at Turnagain Pass.


Mountain Weather

Yesterday:  Mostly cloudy to obscured skies were over the area. Ridgetop winds over the past 24 hours have been moderate (10-20mph) from the east with gusts up to 40mph. Temperatures have climbed overnight and sit in the mid 30'sF at 1,000' and the upper 20'sF along ridgetops this morning.

Today:  Partly cloudy to cloudy skies are expected with a chance for a few raindrops below 1,500' and snowflakes above 1,500'. No measureable precip is forecast. Ridgetops winds will remain easterly in the 15-20mph range with gusts to the 40's. Temperatures should remain warm, with daytime highs up to 38F at 1,000' and 30F along ridgetops. 

Tomorrow:  Unsettled warm weather is forecast to continue with rain and snow showers picking up Thursday afternoon and intensifying on Friday. Our friends at the NWS said this about the upcoming system "The track of the storm favors western Prince William Sound/eastern Kenai Peninsula for some of the heaviest precipitation with strong east to southeast upslope flow. Warm air accompanying the low means most of this will be in the form of rain". The rain/snow like for Friday looks to push into the 2,000' plus range. 

 *Seattle Ridge wind sensor is rimed over. Alyeska Mid Wx Station and Summit Lake Snotel snow depth sensor are not functioning.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33  0.1  13 
Summit Lake (1400') 29  5 (estimate) 
Alyeska Mid (1700') 32  trace  0.23  0.2 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  NE  15  42 
Seattle Ridge(2400') 28  *no data  *no data   *no data  

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 01, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed November 21 due to inadequate snow conditions. #hopeforsnow
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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
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