Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, December 2nd, 2016 - 7:00AM
Expires
Sat, December 3rd, 2016 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A MODERATE avalanche danger exists in the mountains surrounding Turnagain Pass at all elevations above 2,000′ and on all aspects. Wind slab avalanches around a foot thick will be possible to trigger on slopes loaded by the new snow from Wednesday night. Larger slab avalanches are also possible in areas less traveled where a weak layer remains in the snowpack 2-3′ deep. Safe travel protocol will be essential today and into the weekend.

***Observations from the Summit Lake area on the Kenai are showing a similar snowpack. Weekly summaries will begin tomorrow morning.  

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Fri, December 2nd, 2016
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
No Rating (0)
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
No Rating (0)
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

A fast hitting and very interesting storm rolled through Wednesday night and into Thursday morning. We were excited to find 12″ of storm snow in the Seattle Ridge parking lot yesterday, but disappointment set in as only 6-8″ was found at the higher elevations. This seemed to be the case with the other ridgelines. In the end, this storm looks to have been a bit more blow than snow. That said, lingering wind slab avalanches are our primary concern today. 

WIND SLABS:  If you are headed out, watch for both older slabs from Wednesday’s storm and fresh slabs if the cold North winds bump up enough to move snow around. Most concerning is that wind slabs could be sitting on the Nov 16 layer of buried surface hoar. If this is the case, a ‘typical’ wind slab avalanche could step down and trigger a much larger slide releasing 2-3′ deep. Keep in mind, these could pop out mid-slope as the Todd’s Bowl image below illustrates. Pay attention to how the snow feels underfoot. Is it stiff? Does it feel upside down i.e. hard over soft? Do you see shooting cracks? Does it feel or sound hollow? Look for recent cornices, wind pillows and drifts. Is a slope cross-loaded or top-loaded? 

Photo below: Natural avalanches in Todd’s Bowl during the tail end of Wednesday night’s storm. It is suspect that buried surface hoar was the weak layer in the two avalanches where the crowns can be seen mid-slope. 

 

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

A layer of buried surface hoar, 1-3′ deep, still remains on many slopes at Turnagain Pass and in the Summit Lake area. During the past two weeks, many popular slopes have avalanched (removing the weak layer), been covered again by snow and folks are skiing and riding them without incident. The trick is: figuring out where it has not avalanched and could it still? Questions to ask as we move into a weekend of clear-ish skies. Safe travel protocol is your best bet out there in case one of these deeper slides occurs.

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

It’s been roughly a week since we have seen or heard of a glide crack releasing – but the cracks continue to widen despite the cold weather. Once again, limiting your exposure under these is highly recommended. 

Weather
Fri, December 2nd, 2016

Partly cloudy skies aloft with valley fog below filled the region yesterday. No precipitation fell during the day. Winds were light from the Southeast. Temperatures were in the mid 20’s F at all elevations with a spike to 30F at 2,000′ mid-day.

Overnight, an inch of snow fell in Girdwood Valley and Turnagain Pass with light easterly ridgetop winds. Today, continued flurries could pile up another inch. Ridgetop winds will shift to the North this morning and increase to 15-25 mph while ushering in a very cold air mass. Temperatures should drop today from ~25F to 10F on the ridgelines.  

Tomorrow and through the weekend, the cold North flow will remain in place bringing partly sunny skies, cold Northerly winds and little chance for precipitation.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 26    1 0.1   23  
Summit Lake (1400′) 23   0   0   4  
Alyeska Mid (1700′) 26   1   0.1   13  

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  23  NE 7   21  
Seattle Ridge (2400′)  25   SE   7   19  
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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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