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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Heather Thamm  
Wednesday, November 30th 2016
Created: Nov 30th 6:07 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.
0 NO RATING Below Treeline / Below 1,000'
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Special Announcement

TONIGHT!!!


The Bottom Line

The avalanche danger will start out as MODERATE in the alpine, and could easily increase to CONSIDERABLE throughout the day depending on how much snow falls. Triggering a slab 1 - 3 feet thick will become likely if we receive the higher snowfall amount, up to 15 inches. Cautious route choices and conservative decision making will be essential to adapt to today's changing weather. 

Expect a MODERATE avalanche danger today at treeline where triggering a storm slab up to 1' thick is possible depending on snowfall amounts.


Primary Concern

A low pressure system in the Eastern Gulf will combine with cool Northern arctic air over Southcentral Alaska today. There is a “fair amount of uncertainty on snow amounts” impacting Turnagain Pass, but expect snow totals to be anywhere between 5-15 inches.  Moderate Easterly winds (10-25mph) are also expected which could easily increase the avalanche danger throughout the day especially if snowfall intensifies. It will be important to adapt your travel plans to changing weather conditions and be on the lookout for any signs of instability; shooting cracks, whumphing sounds, or recent avalanches.

Don’t forget what this snow is falling on. A reactive layer of buried surface hoar from Nov.16 lies below 1-2 feet of old snow. This widespread layer exists on all aspects and has been the culprit in dozens human triggered avalanches over the last two weeks including the most recent on Sunday Nov.27 in Seattle Creek area. Today’s weather has the potential to re-load this weak layer increasing the likelihood for human triggered avalanches. Slab depths could be as thick at 1.5-3 feet thick depending on snowfall amounts. Cautious route choices and conservative decision making will be essential today.

Buried surface hoar is still a very visible layer and continues to be reactive in tests pits. Photo taken at 3200' on a SW aspect of Tincan on 11/27 by Aleph Johnston-Bloom


Secondary Concern

Today’s new snow will be falling on weak old snow; snow that has been 'faceting' due to cold temperatures this week. The combination of wind and the possibility of higher snowfall totals (up to 15") could produce storm slabs 1’ thick both in the alpine and at treeline.

 


Additional Concern

Watch for glide cracks and remember to limit time under these, there have been a handful that released last week. *Several cracks have been opening in popular terrain like Tincan’s Common bowl and the SW face of Sunburst.


Mountain Weather

Yesterday was cold and clear. Temperatures were in the single digits and light to moderate ridgetop winds made for a  windchill of -5F to -20F below zero. Winds varied from North to Southwest and no new precipitation was recorded. 

Today 5-15 inches of snowfall (up to 0.5 inches of water) is expected today in the upper elevations of Turnagain Pass. Temperatures will start out cold and warm up in to the 20F’s  throughout the day. Easterly ridgetop winds are expected to be moderate (10-25mph.)

Tonight and tomorrow more snow is expected throughout the region. Its hard to say how much will impact our area, but temperatures are staying cool enough that it should all fall as snow.    

***We are happy to report as of 3pm yesterday Sunburst Weather Station is back online!

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 0 17 
Summit Lake (1400')
Alyeska Mid (1700')

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 5***  Variable***  6***  27*** 
Seattle Ridge(2400') NW  11  39 

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: Nov 18, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedOnly a few inches of snow sits at the motorized lot, not enough to open for snowmachining at this time. Updated Nov. 18, 2017
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

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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
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
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