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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Tue, April 19th, 2016 - 7:00AM
Expires
Wed, April 20th, 2016 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is  CONSIDERABLE  today below 2500′ due to an active glide avalanche cycle. Destructive glide avalanches are occurring daily across the region and its important to  avoid being under the runout of glide cracks.  In addition to glide avalanches, natural wet loose avalanches are possible today.  In the Alpine where the avalanche danger is generally  LOW,  be aware of blowing snow that could form small isolated wind slabs in steep terrain.

***Travel is not recommended in avalanche terrain on the West (motorized side of Turnagain Pass).

*ATTENTION HIKERS:  Summer use areas crossing under avalanche terrain should be avoided due to the possibility of natural avalanche activity. Byron trail in Portage Valley and Crow Pass are two examples of trails with dangerous avalanche terrain above.

AVALANCHE OUTLOOK for Wednesday, April 20th:  

Wednesday looks to be very similar to today. In general all the avalanche instabilities that have been mostly confined to the 1000′-2500′ elevation band may slowly creep into the Alpine and become more of an issue as temperatures remain warm with periods of rain and sun. Be aware of wind slabs and wet snow in the alpine, where the avalanche danger could increase to  MODERATE.

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Tue, April 19th, 2016
Alpine
Above 2,500'
Low (1)
Avalanche risk
Treeline
1,000'-2,500'
Considerable (3)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Low (1)
Treeline
1,000'-2,500'
Avalanche risk
Considerable (3)
Below Treeline
Below 1,000'
Avalanche risk
No Rating (0)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • 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

In the Treeline zone (1000’-2500’) the avalanche hazard remains complex due to glide avalanches that threaten access to safer snow in the Alpine. Our biggest concern remains focused on the motorized uptrack where two large glide avalanches recently on Repeat Offender including one shortly after 5:30pm yesterday. Considering how many more cracks threaten this zone, we are recommending that people not travel on the uptrack or in runout areas along Seattle Ridge.

On the non-motorized side of the road be aware of new cracks forming in popular terrain, like the West face of Cornbiscuit and Magnum. Our message remains the same: AVOID being under glide cracks and respective runout zonesTo be in the wrong place at the wrong time when a glide releases could likely be deadly.

Photo on right side was taken yesterday afternoon. This new glide avalanche occurred within the last two days and more glides threaten the uptrack.

 

 

 Close up of glide cracks above the uptrack on Seattle Ridge.

Avalanche Problem 2
  • Wet Loose
    Wet Loose
Wet Loose
Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
More info at Avalanche.org

Over the last few days wet loose avalanche activity has slowed down in Turnagain Pass due to a deeper freeze in the mid elevation band. However outside of our core advisory zone, in Portage Valley, natural avalanche activity has been observed in steep channeled terrain along the Byron Glacier Trail. Extra caution is warranted in this particular area and leaving the established trail is very dangerous. Today there is possibility of both rain and sun, both of which will increase the potential for natural wet loose avalanche activity in this particular zone.

In the mid elevation zone where wet snow is falling on a hard surface triggering wet loose activity will be likely on steep terrain where the surface snow is wet. If the sun makes an appearce today small natural wet loose activity will be possible on solar aspects in the alpine. Pay attention to snow depths; wet ‘sluffs’ will be proportional to the amount of snow that falls today.  

 Video taken on 4/17 by a public observer who witnessed an avalanche close to the Bryon Glacier trail while hiking. 

Additional Concern
  • 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

In the Alpine there is currently not a lot of snow available for transport, but 2-3” of new snow is expected today. This combined with 20-30mph winds could form small isolated wind slabs on steep features in the alpine. Blowing snow and soft-pillowed shaped formations are clues that wind slabs are forming. 

Cornice fall – Where cornices are large be skeptical of their stability. Recent cornice fall has been observed, and in some area these features are gigantic. Give them lots of space and don’t hang out underneath one. 

Weather
Tue, April 19th, 2016

Yesterday skies were mostly sunny and daytime temperatures reached the mid 50F’s near sea level. At Center Ridge Weather station (1880′) daytime temperatures were in the mid 40F’s and overnight temperatures hovered just above freezing. Easterly Ridgetop winds were light increasing the moderate overnight.

Today Scattered rain showers are expected throughout the day with mostly cloudy skis, but periods of sun are always possible. Rain/snow line will be around 2500′ with an addition 0.2 € of (snow water equivalent) expected today, 2-3 € of snow in the alpine. Ridgetop winds, averaging 20-30mph, will be from the East.   Daytime high temperatures for 1000′ are expected to be around 45F and overnight lows in the mid 30F’s.

Similar temperatures and showery conditions are expected tomorrow, before another possible window of clear skies on Thursday.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 38   1   0.1   108  
Summit Lake (1400′) 37   0   0   25  
Alyeska Mid (1700′) 37   trace   0.18   93  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 29   NE   11   32  
Seattle Ridge (2400′) 31   SE   14   35  
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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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