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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, January 21st, 2016 - 7:00AM
Expires
Fri, January 22nd, 2016 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

Today a MODERATE avalanche danger exists in the Alpine and at Treeline. Triggering an isolated wind slab 6 €-20 € thick is possible on steep wind-loaded features. In places protected from the wind loose snow avalanches could be fast moving and easily knock you off your feet in the wrong place. Identify wind-loaded features, turn around if you see shooting cracks, and be conservative near high consequence terrain. Also avoid slopes with glide cracks and give cornices a wide berth today – both of these hazards are unpredictable.

A LOW avalanche danger exists below 1000′ where triggering an avalanche is unlikely.

If you are thinking of going to Summit Lake, be aware that different avalanche hazards exist within the snowpack. Click HERE to read the Summit Lake Summary from this last weekend.  

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Thu, January 21st, 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

Wind slabs: Over the last few days several wind events combined with over a foot of new snow have created fresh wind slabs up to 20” thick on leeward features. The good news is this new snow is bonding well with the old snow below, however not enough time has passed for this hazard to have completely healed. Wind slabs are likely to be tender and found on slopes steeper than 38°. Trigging an isolated wind slab in the wrong place, like over a cliff or above a terrain trap, could have high consequences.  Should today’s visibility allow for easy access into steeper terrain avoid wind-loaded features, watch for shooting cracks, and choose your terrain wisely.

Cornices: Already large cornices have received additional stress over the last 3 days.  Strong winds have been adding weight to their robust size and could be extra tender today. These backcountry bombs have a tendency to break farther back than expected and can send you for an undesirable ride.  Approach ridgelines with caution and avoid being on or directly below cornices features. 

Yesterday’s poor visibility prevented a view into the alpine, but here’s a photo from Tuesday, Jan.19th, of Tincan Proper. Note the large cornice near the ridge and wind-loaded pillow features. Above photo by Aleph J-Bloom

 

 

An observation yesterday from Seattle Ridge showed good bonding of new snow and old snow – however tender windslabs are suspect in steep terrain. Photo by Wendy Wagner 

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

In places protected by the wind 12” of loose unconsolidated snow could be fast moving in steep terrain. Loose snow can easily knock a person off of their feet or take them for a ride over a cliff or into a terrain trap. Manage your ‘sluff’ by letting loose snow move past you and avoid terrain features with high consequences. 

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

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 as we have seen over the past few days. 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. The new snow has made it harder to see the existing cracks and glide releases in the terrain. 

It is best to give glide cracks a wide berth.  Avoid spending time 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 and bringing the entirety of the snowpack with them. 

Close up comparision of a glide crack on the East face of Seattle Ridge that released suddenly on Jan.16. These glide releases are now covered with fresh snow and harder to see. 

 

Weather
Thu, January 21st, 2016

Yesterday 5 € of new snow was recorded at Center Ridge weather station. Temperatures increased into the low 30’s F at 1000′ causing wet heavy snow to fall along the road. Ridgetop winds were light from the Northeast.

Overnight precipitation stopped and temperatures cooled into the high 20’s.

Today expect valley fog in the morning. Skies are expected to be mostly cloudy. There’s a chance of light snowfall by early afternoon. Expect temperatures to increase into the low 30’s F and wind to be light from the Northeast.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 30   5   0.5   88  
Summit Lake (1400′) 31   0   0   27  
Alyeska Mid (1700′) n/a   n/a   n/a     n/a    

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 25   NE   14   44  
Seattle Ridge (2400′) 26   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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