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 16th, 2017 - 7:00AM
Expires
Tue, January 17th, 2017 - 7:00AM
Forecaster
Heather Thamm
The Bottom Line

The avalanche danger is MODERATE today in the mountains surrounding Turnagain Pass at all elevations and on all aspects. Wind slab avalanches will be possible to trigger on slopes over 35 degrees that have been loaded by winds. These slabs are expected to be relatively soft, in the 1-2′ thick range and could be lower on slopes due to cross-loading. Northern aspects and areas with a shallow snowpack are suspect of deeper instabilities where a triggering a slab up to 2-3′ thick is possible.  

Ice climbers and hikers:  In Portage Valley and other areas where climbing routes and trails sit under avalanche paths, be aware that debris from a natural avalanche above is possible.  

*In the Girdwood Valley, where more snow fell on Friday, there is a heightened danger as a slab avalanche triggered could be 2-3′ thick on wind loaded slopes.  

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Mon, January 16th, 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

Yesterday afternoon only a trace of new snow fell, but blowing snow was observed most of the day and weather stations in Turnagain Pass reported moderate Easterly winds 15-30mph during most of the day light hours. This was in addition to moderate Easterly winds that coincided with about 10-12” of new snow the day before. Yesterday’s winds were from the SE on Seattle Ridge and NE at Sunburst, which may have caused slightly different loading patterns on each side of the road. In general Western aspects will be more loaded, but cross loading will range from NW to SW slopes where triggering a wind slab 1-2’ thick will be possible today on slopes steeper than 35 degrees. Several inches of low density snow has fallen overnight without much wind and this may make it challenging to see wind loading patterns. As you travel today be on the look out for obvious signs like shooting cracks and be aware of terrain that may have high consiquences. These slabs are likely to be soft and could be lower on slopes where cross loading may have occurred. 

Red Flags to look for:

  1. Recent Avalanches
  2. Cracks that shoot out from your snowmachine, skis or snowboard
  3. A transition from soft snow to stiffer feeling snow when climbing to exposed areas or higher elevations affected by winds
  4. Texturing of the snow surface (may be difficult to see with a few inches of new snow) 

 ***Loose snow sluffs are also possible on the steeper slopes and these could run further than expected.

Avalanche Problem 2
  • 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

Northern aspects remain suspect of deeper instabilities where 1-2’ of new snow is sitting on a shallow snowpack with poor structure. Yesterday an observations confirmed evidence of two natural avalanches (occurring some time between 1/13-1/14) on the North facing slopes of Sunburst. Several snow pits on adjacent NW slopes revealed poor structure with some propagation potential in deeper layers of the snowpack. This structure is more common on the Southern end of Turnagain Pass (Magnum to Johnson Pass) where a much shallower snowpack exists. It will be in these areas where triggering a slab in a deeper layer of the snowpack may be easier and possible on any aspect.  

In the lower elevations below 2000’ buried surface hoar is sitting below 8-12” of new snow. Multiple observers yesterday found this layer on Tincan and Eddies. The Alaska Avalanche School found evidence of two small soft slab avalanches on Tincan, possibly remote triggered mid-storm two days ago. These were small, only a foot deep and 20’ wide, but were also on small terrain features. In the lower elevations it may be possible to trigger a soft slab on steep unsupported terrain features or along gully’s. This could be more of a concern below treeline in places like Portage or Placer Valley, where ice climbers and hikers should be aware of the terrain above and avoid being in the run-out of large steep slopes.

A North aspect adjacent to one of two crowns found on the North side of Sunburst. Tests results were mixed, but found propagation potential in a uniform layer of facets sitting between two wind slabs 16″ below the surface. 

 

Two small soft slabs at 1400′ on Tincan that likely released on 1/14 near the end of the storm. Observers dug pits near by and found buried surface hoar to be the weak layer. Prior to this storm buried surface hoar was found below 1500′ in many places throughout Turnagain Pass. 

 

 

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

Yes, we are still concerned about glide cracks releasing. Most of the cracks we know about are in areas rarely traveled. The exception is in -1 Bowl (Main Bowl) in the Seattle Creek drainage where glide cracks threaten terrain commonly traveled. Keep an eye out for cracks, which can be difficult with new snow, and limit time underneath them.

Weather
Mon, January 16th, 2017

Yesterday skies were overcast becoming obscured by mid afternoon. NE ridge top winds averaged 15 with gusts in the 30’s mph mid-day becoming light from the NW by the evening. Temperatures averaged around 15F cooling to 10F by late evening. Yesterday afternoon to this morning 3-4 € of new snow was recorded at Center Ridge and at the mid way station at Alyeska. Other areas of the Pass only received a trace total overnight.

Today an additional 1-3 inches of snow could fall by late morning with scattered snow showers in the afternoon. Winds will remain light from the NW and temperatures will be around 10F dropping near 0F by this evening.    

Cold arctic air over mainland Alaska is expected to bring subzero temperatures to Southcentral, Alaska through the remainder of the week. Skies will be clear with a light Northwest winds.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 14   4   .3   45  
Summit Lake (1400′) 9   1   .2   15  
Alyeska Mid (1700′) 12   5   .35    43

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′) 12   ENE   10   35  
Seattle Ridge (2400′) 9   SE   12   46  
Observations
Recent Observations for Turnagain Pass
Date Region Location
12/10/19 Turnagain Avalanche: Tincan and Sunburst from the air
12/10/19 Turnagain Observation: Tincan
12/08/19 Turnagain Avalanche: Tincan
12/06/19 Turnagain Avalanche: Sunburst
12/04/19 Turnagain Observation: Sunburst
12/03/19 Turnagain Observation: Hippy Bowl
12/01/19 Turnagain Observation: Tincan, All elevations
12/01/19 Turnagain Observation: Tincan
11/30/19 Turnagain Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge
11/29/19 Turnagain Observation: Sunburst Ob #2
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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