Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, January 6th, 2016 - 7:00AM
Expires
Thu, January 7th, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

Today the danger at Treeline and above Treeline is  MODERATE. The likelihood of triggering a Wind Slab avalanche  2-4′ deep is possible above 1000′. These slabs are most likely to be triggered on steep  leeward  slopes. Large fresh cornices loom above much of this same terrain and should be avoided. For the periphery of the core Turnagain advisory zone (Girdwood Valley and south towards Summit Lake) where the overall snowpack is thinner elevated caution is advised. There are still buried weak layers that have been reactive and could produce a Deep Slab avalanche.

Human triggered avalanches are possible today. Don’t let the sunshine effect decision-making.  Identify steep terrain and areas of concern, evaluate the snowpack carefully, watch for signs of instability and practice safe travel techniques.

Below 1000′ the danger is LOW.  

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Wed, January 6th, 2016
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

With sustained winds averaging in the mid-50’s mph on Sunday (and gusts to 101mph on Sunburst)  2-4′ thick wind slabs are possible on steep leeward slopes, particularly above treeline; though it is worth recognizing that strong winds such as these have a tendency to load slopes far below ridgelines, creating a mid-slope avalanche problem. There was significant cross-loading as well. Identifiying where the winds deposited the snow is crucial. Look for pillowed snow, listen for hollow sounds and pay attention to stiff snow under your skis, snowboards or snowmachines. Watch for shooting cracks and remember even a small pocket of wind slab in steep terrain can have high consequences. Wind slabs are notorious for letting you travel out onto them and then breaking above you. Evalute carefully before commiting to steep terrain from above or below.

Avalanche Problem 2
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Sustained winds, relatively warm temps and moist snow have continued to grow large cornices.  These have the potential to fall naturally or be triggered by the weight of a person or machine and can be very dangerous. Travel under or on them should be avoided. They have the tendency to break farther back from the ridge than expected and can trigger an avalanche on the slope below by adding a lot of weight quickly. As you approach ridgelines and the entrances to backcountry bowls make sure you aren’t accidently traveling on overhanging snow. 

Additional Concern
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

In some parts of the advisory area now sitting under 5-7′ of settled storm snow is a layer of old faceted snow on top of the Thanksgiving Rain Crust. This still needs to be a consideration as you travel into the backcountry today. This is a low probability, very high consequence set-up.  It is important to use safe travel practices and do not overload slopes with multiple skiers, boarders or snowmachines. Limiting your exposure time spent underneath large paths such as those that effect areas like Johnson Pass and the Lynx Creek drainage.  In addition we have limited snowpack information from Johnson Pass and Lynx Creek but we know that the snowpack is shallower. The surface hoar that developed prior to Christmas may be buried and preserved especially near the creek. Watch for signs of instability: recent avalanches, shooting cracks, collapsing and whumpfing. Pay attention to snow depth and trigger points. Deep slabs are most easily triggered from shallow spots where the weight of the traveler can more easily effect the weak layer. 

NOTE:  In areas such as Summit Lake, the snowpack is shallower and harbors more weak layers under the recent storm snow.  See Wendy’s observation and write-up from a snowboarder-triggered avalanche (Saturday) that failed on a buried surface hoar layer that ran on a mellow (28-30 degree) slope.

 

Weather
Wed, January 6th, 2016

The stormy weather moved out yesterday, skies cleared and winds died down. The winds were Easterly in the morning 15-25 mph, gusting in the 50’s and then shifted to the west and have been light overnight. Temperatures were in the mid 20Fs at ridgeline and 30Fs at 1000′.  There was a cooling trend overnight.  

Today will be mostly clear and sunny as we have a break inbetween storms. Temperatures will be in the mid 20Fs to mid 30Fs. Winds will be light and Westerly. The clouds will build again this evening and there is chance of snow showers overnight and tomorrow. The next Low is forecasted to move into the Gulf and effect the forecast area into the weekend.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30   0   0   85  
Summit Lake (1400′)  27 0 0  27
Alyeska Mid (1700′)  32 0 0  32

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 24   ENE   15   56  
Seattle Ridge (2400′) 25    n/a n/a   n/a  
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Riding Areas
Updated Mon, December 02nd, 2019

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

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

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