Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, January 23rd, 2017 - 7:00AM
Expires
Tue, January 24th, 2017 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

There is a  MODERATE  avalanche danger in the mountains surrounding Turnagain Pass for a variety of avalanche concerns. First, wind slab avalanches around 1 foot thick will be possible to trigger above treeline on slopes that get loaded today and that were loaded over the past two days. Second, on the steeper terrain that has seen little wind effect,  expect to trigger sluffs that could be high volume and run far. Lastly, in the lower elevations (below  2,000′, such as the Placer Valley area), watch for persistent soft slab avalanches 12-18″ thick that could release on a layer of buried surface hoar. Watch for changing conditions. If the approaching storm arrives earlier in the day than forecasted the danger could rise to CONSIDERABLE.

Practice safe travel protocols, always carry rescue gear and please let us know what you see out there!!! Thanks to everyone who sent in observations over the weekend!

Girdwood Valley:  10″ of new snow fell yesterday adding to the 8″ that fell the day before. Slabs and loose snow avalanches (sluffs) both have the potential to be larger due to more snow.  

Summit Lake:  Higher snowfall amounts fell on a generally weaker snowpack.  Please check out the Saturday Summit Summary  HERE.  

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Mon, January 23rd, 2017
Alpine
Above 2,500'
Moderate (2)
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
Moderate (2)
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

Winds are increasing this morning as the next storm approaches. A few more inches of snow are forecasted to fall during the day and there is plenty of soft snow available to transport and to form tender wind slabs in the Alpine. Heavier, wetter snow falling today may make slabs more reactive. In addition, older wind slabs that formed over the weekend may also be triggered on steep leeward slopes. There was one skier triggered slab yesterday on a South facing slope on Lipps. In this avalanche the wind slab was resting on old hard wind crust from the wind event prior to the storm. This combination has been found in steep leeward terrain the past two days. Feel for hollow feeling snow, stiffer snow over softer snow or slab sitting on hard snow and watch for cracks that shoot out from your snowmachine, skis or board. 

Skier triggered slide on Lipps 1.22.17. Photo: Mike Records

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

There is a significant amount of loose snow from not only Saturday’s storm but the snowfall earlier in the week. Expect sluffs to be triggered on slopes approaching 40 degrees. These are likely to be high volume and run fast and far. Sluff management will be key. In Girdwood Valley these will have more volume due to additional 10″ that fell yesterday. 

 

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

A variety of persistant weak layers exist within the snowpack and vary across our region. In most cases these layers have been generally dormant. As more load is added and the slab develops they have the potential to become more reactive. In shallower parts of the area there are developed basal facets and in many locations there is a mid-pack layer of facets from December. At the lower elevations, below 2,000′, a layer of buried surface hoar exists under the last two snowfall events (12-18″ below the surface). Slab avalanches failing on this layer are possible where the snow on top is stiff enough to form a slab. In most locations, the snow is too loose and therefore triggering a slab in unlikely, but it seems the party on Cornbiscuit Saturday may have found one of these lower slopes that did indeed have enough of a slab on this suspected buried surface hoar. The lower terrain in Placer Valley is an area that may have a similar set up. All of these layers are important to remember if we receive a significant load in the next couple of days!!!

Surface hoar layer that was buried on January 13th. Photo from Eddies on January 17th. This layer has been found in a number of locations below 2000′ in the advisory area.

Weather
Mon, January 23rd, 2017

Yesterday was mostly cloudy with snow showers until late afternoon. Girdwood Valley saw consistent snowfall through most of the day with 10″ of low density of snow falling. Turnagain Pass only received an inch and skies cleared in the late afternoon. Winds were light and temperatures were in the teens. Overnight temperatures started to slowly rise and winds picked up early this morning.

Today skies will be cloudy and snow showers are expected with 1-5″ possible. Easterly winds will be 15-25 mph gusting into the 30s. Temperatures will rise into the 20Fs. Tonight the precipitation intensity is forecasted to increase with potential for over a foot or more of snow to fall. There is still some uncertainty about what the temperatures will be and the rain/snow line as the storm continues into tomorrow. Easterly winds will also increase overnight.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 14    1 .2    46
Summit Lake (1400′)  12  0  0 25
Alyeska Mid (1700′)  14  10  .5 49  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 14    ENE 7   19  
Seattle Ridge (2400′)  13 SE    15  22
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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