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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, January 11th 2016
Created: Jan 11th 6:47 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.
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
The Bottom Line

Today we have a CONSIDERABLE avalanche danger at the Alpine elevations in, and surrounding, Turnagain Pass. Wind slab avalanches 1-2' feet thick will be likely for people to trigger on slopes around 35 degrees and steeper. Cornices are also expected to be touchy today and could trigger an avalanche below. Areas at the Treeline elevations have a MODERATE danger for wind slabs in exposed locations as well as glide avalanche potential. 

*If skies clear today for travel above treeline, careful snowpack evaluation and cautious route-finding are recommended. The most likely place to trigger an avalanche will be where winds have loaded, or are actively loading, slopes. 

In areas such as Summit Lake, the snowpack is shallower and harbors more weak layers. Click HERE to read Saturday's Summit Lake Summary. 


Primary Concern

After two warm Pacific storms moved through over the weekend, it seems we will get a break in weather for the next few days. Precipitation and snowfall totals from Friday through this morning are listed below. The numbers are in 'water equivalent'. The rain/snow line has been fluctuating between 1,000' and 2,000' during this three-day stretch.

                             Friday       Saturday     Sunday                                 STORM TOTAL
Turnagain Pass      1.1      +      0.4       +    1.4        =        2.9" water equivalent (~20" dense snow)
Girdwood Valley     0.7      +      1.2       +    0.8        =        2.7" water equivalent (~20" dense snow)
Summit Lake             0      +      0.1       +    0.1        =        0.2" water equivalent (~2" dense snow)

Due to very limited visibility yesterday, we do not have information for the Alpine elevations. We can expect however, with dryer snowfall (adding 10-12" yesterday) at these higher elevations and strong winds, natural wind slab avalanches, as well as cornice falls, were occurring. With the possibility for clearing skies today, things to watch for will be wind slab avalanches and cornices. Keep in mind:

- Easterly ridgetop winds are forecast to remain strong enough to transport snow above treeline today (20-30mph)

- Although winds are generally Easterly, they can be channeled by the terrain and load, or cross-load, a variety of aspects

- Watch for, and steer clear of, slopes being actively loaded

- Watch for smooth rounded surfaces and hollow feeling snow, stiff snow over softer snow

- Informal tests, such as sticking your boot (or pole) in the snow to feel if softer snow sits under stiffer snow, can be great ways to assess if there is a wind slab. This should be done on low angle slopes without avalanche potential before venturing onto steeper terrain.


Secondary Concern

Cornices have grown considerably during the past few weeks. Not only do they have the potential to fall naturally, but also to be triggered by the weight of a person or snowmachine. They can also trigger an avalanche below and, all in all, be VERY dangerous. Travel under or on them should be avoided. And remember, they have the tendency to break farther back from the ridge than expected. 


Additional Concern

Glide cracks have been appearing throughout Turnagain Pass over the last couple weeks. As you travel through the backcounty this week, pay attention for large open cracks in the snow, 'crevasse looking' features, these can release spontaneously without any warning. Similar to managing cornices, it is best to avoid traveling on or under slopes with glide cracks. 

Photo below was sent to us yesterday from Turnagain Pass. These glide cracks are in the Treeline elevation band (between 1,000' and 2,500'). Although the cracks are slightly obscured by yesterday's snowfall, you can still see them looming. 


Mountain Weather

Yesterday's pulse of moisture ended up being a bit more potent than forecast, as mentioned above. Turnagain Pass saw roughly 10-12" of snowfall above 2,500' and rain at the road elevation. Along with the snow and rain, ridgetop winds were strong, blowing in the 30's and 40's mph with gusts over 70mph. Temperatures were warm, 37F at 1,000' with a rain/snow line hovering right around 1,600' (give or take).

Today we should see skies begin to breakup and precipitation to continue to diminish. Ridgetop winds, on the other hand, are forecast to remain moderate to strong from the East - averaging in the 20-30's with stronger gusts. Temperatures will remain warm as well, in the mid 20's F on the ridgetops and near 35F at 1,000'. 

Tuesday through Thursday it looks like we should have a break between storms. Temperatures are forecast to cool slightly, skies clear off and winds shift to a Northerly direction. Stay tuned.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')   31  1.4  91 
Summit Lake (1400')  35  0.1 27 
Alyeska Mid (1700')  33 0.75  64 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  NE 40  78 
Seattle Ridge(2400') 27  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: Apr 11, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: OpenWide swaths of open river in the Placer Valley. Travel with extreme caution!
Skookum Drainage: ClosedSKOOKUM DRAINAGE CLOSED TO MOTORIZED USE ON APRIL 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: ClosedClosed for the remainder of the 2017 season.
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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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
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