Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, February 13th, 2017 - 7:00AM
Expires
Tue, February 14th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

Heavy snowfall, rain and strong winds are creating a  HIGH  avalanche danger at all elevations in the Turnagain Pass area, this includes Portage, Placer and Girdwood Valley. Travel is not recommended in avalanche terrain where natural avalanches are likely occurring due to rapid loading.  

 

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Mon, February 13th, 2017
Alpine
Above 2,500'
High (4)
Avalanche risk
Treeline
1,000'-2,500'
High (4)
Avalanche risk
Below Treeline
Below 1,000'
High (4)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
High (4)
Treeline
1,000'-2,500'
Avalanche risk
High (4)
Below Treeline
Below 1,000'
Avalanche risk
High (4)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • 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

New snow and wind have combined to create very unstable slabs, 1-3’ thick.  Ridgetop winds from the East (SE to NE) picked yesterday afternoon and ramped up into the 40s and 50s mph overnight with several gusts in the 90s at Sunburst weather station. An additional 5-15″ of snow is forecasted for the higher elevations today and will increase the size of these slabs. These slabs will release naturally in steep terrain and could step down into older layers in some locations. Natural avalanches could run the full length of a slope, thus it will be important to avoid being near any runout zones today. Winds and continued precipitation will make natural avalanche activity likely throughout the day. There is some uncertainty with rain/snowline today. It is already 32F at Center Ridge and raining in Girdwood. Rain may fall as high as 2000′ today and the warming trend is forecasted to continue into tomorrow. Rain on snow will also increase the likelihood of natural avalanche activity at lower elevations. It is important to remember that the heavier, wetter new snow and/or rain is falling on lighter low density snow from Friday’s storm and loading a layer of buried surface hoar and small facets. Avalanche activity is expected at all elevations and aspects. This set up could be a hazard even in the Tincan Trees.

This is not a complicated situation.  Avoidance of avalanche terrain is the only way to “manage” this problem today. 

Sunburst Weather Station this morning. Strong winds and dramatic temperature increase. Note the gusting into the 90s. 

 

 

Avalanche Problem 2
  • 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

Weak snow (facets and depth hoar) in the lower layers of the snowpack continues to be a concern in our advisory area. Today avalanches occurring in the upper layers have the potential to step down and release the entire snowpack in some places. If this does happen the volume will be large and could run long distances. 

Travel in avalanche terrain is not recommended today including being in the runout of a steep slope, like in the flats below Seattle Ridge. 

Question of the day: When will we reach the tipping point to activate these weak layers at the base of the snowpack? 

Weather
Mon, February 13th, 2017

Yesterday started out with clear skies in the early morning. Clouds moved in and precipitation started early afternoon. Snowfall and winds picked up around 2 pm with over a foot of snow falling overnight. Easterly (SE-NE) winds averaged in the 40s and 50s with gusts into the 90s. Temperatures dramatically rose throughout the day starting around 0F or single digits in the morning and rising to the high 20Fs to low 30Fs by late afternoon.  

The storm continues today with another 5-15″ of snow forecasted at upper elevations. Winds will continue to be easterly 20-40 mph with gusts into the 60s. Temperatures will be in the 30Fs in the valleys and the high 20s at ridgetops. The mixing of cold and warm air with the system is causing some uncertainty about the precipitation type and amount. Rain/snowline is hard to determine. There may be rain up to 2000′ or higher or the cold air could stay in place and keep most of the precipitation snow. If you want to read more about it check out the NWS discussion this morning HERE.  

The unsettled weather continues as another a wave of moisture is supposed to impact the area tonight into tomorrow. An additional 1-2′ of snow is forecasted but the temperatures and timing are still uncertain. Stay tuned and think cold thoughts…  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 25   9  1  66
Summit Lake (1400′) 22  2 .4    25
Alyeska Mid (1700′) 23 14  1    62

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  12 ENE    40 93  
Seattle Ridge (2400′)  14  SE 25    59
Observations
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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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