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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, January 14th, 2017 - 7:00AM
Expires
Sun, January 15th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The avalanche danger is CONSIDERABLE  on upper elevation slopes. Human triggered wind slabs 1-2′ thick are likely on leeward terrain and natural avalanches are possible. In areas  unaffected by winds and receiving less snow  the danger will be  MODERATE  where small shallow storm slabs and sluffs in the new snow may be triggered on the steeper slopes.    Girdwood Valley received twice as much snow as Turnagain Pass.

Ice climbers and hikers:  In Portage Valley and other areas where climbing routes and trails sit under avalanche paths, be aware that debris from a naturally occurring slide above may run to these lower elevations.

Check out the Saturday Summit Lake Summary HERE.  

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Sat, January 14th, 2017
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
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

New snow (6+ inches at Turnagain and 12+ inches in Girdwood Valley) combined with moderate winds speeds ESE-ENE 15-25 (gusting to 40 mph) in the last 24 hrs have formed fresh, sensitive wind slabs on leeward slopes. Wind slabs may be 1-2′ thick. These slabs will be sitting on a variety of old surfaces and may not bond well. Slick wind crusts and soft facets covered most of the terrain prior to the storm. Places where the new snow landed on the slick crusts will be especially suspect. Look for new cornice formation, pillowed and drifted snow and cracking. Winds speeds have mellowed this morning but are expected to pick back up this afternoon. Watch for wind transporting snow and avoid travel underneath actively loading slopes as naturals will be possible. 

 Photos: National Avalanche Center 

 

 

Yesterday afternoon. 1.13.17, Snow starting to drift and crack. 

 

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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

In areas unaffected by wind new snow can still act as a slab especially in Girdwood where more snow fell. In addition temperatures warmed up overnight and the storm snow may be slightly upside down with heavier snow over lighter snow. The question during and right after a storm is “How well is the snow bonding to the old snow surface it landed on?” As noted above with the wind slabs, the storm snow landed on a variety of surfaces including slick wind crusts and may not initally bond well. Stepping off the skin track or jumping off your snowmachine to do quick hand pits will be a great tool for determining new snow depth and bonding. Also be on the lookout for loose snow avalanches in the steep terrain where the storm snow may not stick to old surfaces at all. Avoid terrain traps i.e. places where shallow avalanches could pile up more deeply and look for cracking.

As always practicing safe travel protocol is key:

1) Expose only one person at a time

2) Group up in safe zones 

3) Have an escape route planned 

4) Pay attention to other groups. This could be a busy holiday weekend! 

Additional Concern
  • Glide Avalanches
    Glide Avalanches
Glide Avalanches
Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.
More info at Avalanche.org

Glide cracks have been slowing opening this week; though we have not seen/heard of any new cracks releasing. Keep an eye out for cracks, which is difficult with new snow and wind, and limit time underneath them. Main Bowl is one of the spots where glide cracks threaten terrain that is commonly traveled.

Weather
Sat, January 14th, 2017

Yesterday snow fell throughout the day with intensity picking up late in the afternoon. Winds were easterly 15-20 mph with gusts into the 30s and 40s. Temperatures were mostly in the 20Fs with a band of warm air at road level in Turnagain Pass in the 30Fs. Overall temperatures warmed slightly overnight and winds speeds dropped.  

This morning the skies are clearing on Turnagain but snow showers continue in Girdwood. These are forecasted to taper off to partly cloudy skies. Colder air will move in this afternoon with westerly winds to 15-25 mph. Temperatures will drop into the single digits tonight. The next storm system is forecasted to arrive tomorrow with another round of snow into Monday.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 33    7  .6 40  
Summit Lake (1400′)  21  3 .4    14
Alyeska Mid (1700′)  28  13  1.4  35

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  22 ENE   18   40  
Seattle Ridge (2400′)  24  SE  15  29
Observations
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Riding Areas
Updated Wed, December 11th, 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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