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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, November 21st, 2016 - 7:00AM
Expires
Tue, November 22nd, 2016 - 7:00AM
Forecaster
Aleph Johnston-Bloom
The Bottom Line

The    avalanche danger is  CONSIDERABLE  in the Turnagain Pass area on all aspects at elevations near and above treeline.  Human triggered slab avalanches over a foot deep are LIKELY and it is possible they could release on slopes as low angle as 20-25 degrees.  This problem is due to a widespread layer of buried surface hoar underneath recent snow. Additional snow and the wind last night may have made this set-up even more hazardous. Natural avalanches are possible. Cautious route-finding and conservative decision-making are essential.  

At lower elevations, in the trees, a  MODERATE  danger exists where triggering a slab avalanche is possible in open areas or debris running into this zone from an avalanche above is possible.

***The Summit Lake area on the Kenai looks to have a similarly unstable snowpack. Weekly summaries will begin on December 2nd.

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Mon, November 21st, 2016
Alpine
Above 2,500'
Considerable (3)
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
Considerable (3)
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
  • 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

More human triggered avalanches occurred yesterday with reports coming in from both Tincan and Sunburst, including the slope below Taylor Pass sliding. The buried layer of surface hoar continues to be the problem layer. It sits below the new snow from Thursday and has a few additional inches added from the weekend. Slabs have been soft and releasing while people are riding them as well as being triggered remotely from above or the side. With all the snow available for transport and an increase in wind speeds last night the slabs could be even more developed today, stiffer and more hazardous. Slab depths near ridgelines and in leeward areas could be deeper.  Look for cracking in the snow, whumpfing and recent avalanche activity. Low angle slopes have been releasing which is a common with buried surface hoar. Pay attention to slope angle and what the terrain you traveling on is connected to, above and below. Avalanches were triggered onto and close to the skin track on Tincan both Saturday and Sunday.  Please think about where you put skin tracks in and when you are descending make sure you are not skiing or riding on top of other people. 

The new snow and wind will also make it harder to tell what slopes have slid already and wind slabs may be sensitive and exacerbate the problem. Today is another day to be conservative.  Remember the buried surface hoar is widespread and is a persistent weak layer. This means it doesn’t heal/settle quickly and can be reactive for extended periods of time. 

Backlit cross section of snow on Sunburst that shows the buried surface hoar. Photo W. Wagner

Looking up the skin track towards Tincan Common. Low angle avalanche from Saturday below the skin track. 

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

The winds have ramped over night gusting into the 40’s from the ENE. The light fluffy snow that we have enjoyed over the weekend will easily blow around and create fresh sensitive wind slabs that may or may not be sitting on the buried surface hoar. Wind slabs could be reactive either way and may make the slopes with surface hoar even more prone to avalanche.  It will be important to 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. Remember recent wind is a RED FLAG and means something has changed. This is another reason to be conservative today.  How are the mountains channeling the winds? Are slopes being wind loaded?  Can you tell if the slopes are top loaded or cross loaded? Has the wind blown and affected the snow in the trees? 

Photo: National Avalanche Center

 

Weather
Mon, November 21st, 2016

Yesterday was mostly cloudy with snow showers and a few windows of clearing. The winds were light and temperatures were in the low 20Fs. Overnight the winds picked up from the ENE blowing in the 20s and gusting into the 40s. Temperatures rose to the high 20s. 2-5 inches of snow fell in the last 24 hrs.  

Today will be mostly cloudy with a chance of snow showers tapering off in the afternoon. 0-2 inches of snow possible. Winds will be in the 20s and gusty. These should also taper off during the day. Temperatures will be in the high 20Fs.  

There is a clearing trend Tuesday into Thanksgiving Day with sunshine forecasted, light winds and temperatures in the 20Fs. An unsettled pattern returns over the weekend with a chance of snow.  

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880′) 27   5   .4   21  
Summit Lake (1400′)  27  1 .1    3
Alyeska Mid (1700′)  28  2.5  .2  5

RIDGETOP 24-hour data (6am – 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812′)  22  ENE  22  44
Seattle Ridge (2400′)  23 N/A (sensor rimed)     N/A (sensor rimed)      N/A (sensor rimed)  
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Riding Areas
Updated Mon, October 26th, 2020

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
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Closed
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Skookum Drainage
Closed
Turnagain Pass
Closed
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Carter Lake
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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.