Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, November 28th, 2015 - 7:00AM
Expires
Sun, November 29th, 2015 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

CONSIDERABLE avalanche danger exists both in the Alpine and at Treeline. Due to a four day rain event wet saturated snow up to 3′ thick could be triggered below 2500′. At higher elevations heavy snow is sitting on top of cold weak snow below making it possible to trigger a large slab avalanche up to 4′ thick on all aspects. Avoid steep slopes and high consiquence terrain features. Careful snowpack evaluation, cautious route finding and conservative decision-making are essential skills if venturing into the mountains today.  

No Rating below Treeline (below 1000′) means there is currently not enough snow to produce an avalanche at this elevation band.    

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Sat, November 28th, 2015
Alpine
Above 2,500'
Considerable (3)
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
Considerable (3)
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
  • 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 three days 4″ of water fell in the form of rain at lower elevations in Turnagain Pass. Rain/snow line fluctuated between 1800’ and 2500’ leaving the snow saturated with water. Several large wet avalanches were observed along the Seward Highway and Portage Valley over the last two days. Warm temperatures will persist today making it possible to trigger a wet avalanche on steep terrain features. Avoid this hazard by choosing low angle terrain away from large slopes and terrain traps. 

*If temperatures drop below freezing this concern will stabilize quickly as water drains and the slab strengthens in the mid elevation zone. 

Debris from a wet avalanche in Portage Valley. This avalanche likely released on the morning of Nov.27th.

Avalanche Problem 2
  • 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

Strong Northeast winds topped out at 109 mph on Sunburst weather station yesterday morning. Windslabs over 4’ thick on leeward aspects and crossloaded terrain features are a concern for today in the upper elevation zone. Avoid smooth pillow shaped snow on steep slopes and convexities. Even small features if steep enough could break well above you and have plenty of volume to bury a person. Obvious clues like shooting cracks and whumpfing sounds may not be present today making this avalanche problem difficult to identify. 

Additional Concern
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

In the upper Alpine above 2500’ weak faceted snow that formed during a cold snap has been covered up by 4’ of heavy snow creating an upside down snowpack. Last week observations showed a large variation in the distribution of this weaker snow below. It is likely that Northern aspects will harbor the bulk of this problem, but until more information is gathered much uncertainty exists as to how well this new snow has bonded with the older less stable snow below it. This is just one more high consequence reason to avoid steep terrain today. 

Weather
Sat, November 28th, 2015

A very wet and warm storm passed through Southcentral Alaska leaving the region with above freezing temperatures and high-sustained winds for multiple days. In Turnagain Pass rain/snow line reached 2500′, Easterly ridgetop winds maxed out above 100mph and 4 € of water fell over a three-day period.  

Showery weather in the form of mixed rain and snow is expected today and into the weekend with rain/snow line moving to 1000′. Temperatures will hover just above freezing (32F) and begin to cool slightly by this evening. Easterly ridgetop winds 20-30mph are also expected to depreciate by early evening.  This pattern will continue through the weekend with patches of clear sky at times.  

*Seattle Wx Station wind data is currently not available.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 32F   0   1.4   25  
Summit Lake (1400′) 33F   0   0.2 10  
Alyeska Mid (1700′) 34F   0   2.0    13.5

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 26F   NE   23   98  
Seattle Ridge (2400′) 28F   *N/A   *N/A     *N/A    
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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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