Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 13th 2016 7:00 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is MODERATE today at and above Treeline where cornices are looming large over wind-loaded terrain.  In addition, triggering a wind slab 1-3’ in depth is possible on steep (greater than 35 degrees), leeward, upper elevation slopes.

At Treeline, the terrain is littered with glide cracks right now, some of which have avalanched to the ground over the last several days, these pose an unpredictable and potentially very hazardous threat.

Below Treeline the danger is LOW where triggering an avalanche is unlikely.

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

 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.
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.
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Avalanche Problem 1

Today at Treeline (the 1,000’ – 2,500’ elevation band) on all aspects, pay attention to and avoid glide cracks. These can lead to glide avalanches that are very unpredictable.  Weather and other triggers such as humans or even explosives that we associate with other dangerous avalanche problems don’t seem to effect glides in the same way.  There is no discernable pattern to predict a failure as they tend to fail naturally and on their own schedule. Warm temperatures can trigger them and so can cooling temperatures. Cracks can form and release in seconds or days later or sometimes a glide crack won’t release at all, and benignly just fill back in with snow.  

Glide cracks are best to be given a wide berth.  Limit your exposure time spent underneath and if skiing or riding in terrain with glide cracks, try and map them out before your travels so as not to end up directly on top of or inside one.  Remember, when these do fail, they tend to be destructive, failing to the ground bringing the entirety of the snowpack with them. 

Glide crack on Petes North. Photo: Sean Fallon

Avalanche Problem 2

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 on the slope below when they fall. Travel under or on them should be avoided. Remember they have the tendency to break farther back from the ridge than expected. 

Image from the National Avalanche Center


Additional Concern

We saw substantial winds over the weekend (30 – 70 mph from the east) that actively stripped windward slopes and built stiff wind slabs in the alpine.  These may be in the 1-3’ range today and are most likely to be triggered in steep, leeward terrain. Wind loaded slopes are visibly fat right now, be on the look out for shooting cracks, hollow feeling or sounding snow and stiff snow over softer snow. Remember a small pocket of wind slab in can be very hazardous in high consequence terrain. 

Mountain Weather

Yesterday was mostly overcast with a few breaks in the clouds. There were light snow showers, highs were in the mid-20Fs to mid 30Fs. Winds were light and variable.

Today will be mostly cloudy with snow showers throughout the day. New snow accumulation of around 1-3 inches possible. Temperatures will be in the low 30Fs to mid-20Fs.  Winds will be light and shift from east to north. Snow showers continue overnight with a drying trend into tomorrow.

Thursday is forecasted to be mostly sunny and slightly cooler with light northerly winds as we see a break in the active weather pattern that has been affecting the region.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 29   1 .1   86
Summit Lake (1400')  30  0  0  25
Alyeska Mid (1700')  31  1  .06  62


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25  NE*  10*  41* 
Seattle Ridge(2400')  26 n/a  n/a   n/a

*Sunburst anemometer stopped recording at 2 pm yesterday. Wind data is from 6am-2pm.

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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.

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