Avalanche Advisory

Turnagain Area Avalanche Advisory
Tuesday, March 13th 2018 4:48 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

CONSIDERABLE avalanche danger remains above 1000' on all aspects. Large slab avalanches 2-4+ feet thick are likely to be triggered on slopes steeper than 30 degrees. These may be triggered from a distance or from the bottom of a slope. Cautious route finding and conservative decision-making are essential.

MODERATE avalanche danger exists below 1000’ where triggering a large slab avalanche is possible in areas with avalanche terrain like Portage Valley and Placer Valley.

A skier remotely triggered an avalanche on the skin track in Summit Lake yesterday - see Saturday's Summit snowpack and avalanche summary and observations from yesterday HERE. 

 Show the Complete North American Avalanche Danger Scale
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely


Very Large


Yesterday there were 3 reports of skiers and snowmachiners triggering avalanches across the region. A party of skiers triggered two avalanches on Sunburst, one on a deeper buried weak layer. The skier involved in the deeper avalanche was caught, carried, deployed their airbag and ended up off of the debris. A snowmachiner remotely triggered a slab in Grandview and a skier remotely triggered a slide from the skin track in Summit Lake. Today triggering a large and unmanageable slab avalanche 2-4' thick remains our primary concern. Various layers of old faceted snow and buried surface hoar sit under the 2-4 feet of storm snow from Friday. These persistent weak layers have been well documented and are wide spread across our region. During the window of sunshine yesterday some folks ventured out into steeper terrain with no incident while at the same time others were triggering avalanches. Recreating in steeper terrain is a gamble at this point with high consequences if the house wins... 

If you are headed out into the backcountry today things to keep in mind are:

  • The mountains are still adjusting to the several feet of new snow that fell four days ago and there is poor snowpack structure
  • Warming in the afternoon yesterday may also have played a factor in the avalanches being triggered. If the skies clear pay attention to changing conditions.
  • Avalanches can be triggered from the flats or remotely from an adjacent slope - be extra cautious to avoid being in a runout zone 
  • Stick to slopes less than 30 degrees and ease into steeper terrain slowly. Evaluate the consequences if the slope releases; where will the debris go?
  • Listen for whumpfing (collapsing) in the snowpack, look for shooting cracks but realize you may not see signs of instability before the slope releases. 

Sunburst avalanches from below. Photo: Conor Roland

Sunburst avalanches from a different view. The upper one is harder to pick out. 

 Grandview avalanche that was triggered from below, lookers left side.  Photo: Sebastian Landry


Remotely triggered avalanche in Summit Lake. Photo Patrick McCormick

Additional Concern

Wet Loose

Loose Wet Avalanches: Several inches of low-density snow fell this weekend. Wet snow or rain falling could trigger loose wet avalanche activity especially at lower elevations. Radiation from the sun, if it clears later in the afternoon, could also be factor today.  Look for small loose wet sluffs on Southerly aspects in steep rocky terrain. On upper elevation slopes unaffected by rain, wind or sun loose dry avalanches (sluffs) are also possible in steep terrain. 

Wind slabs: Shallow wind slabs formed on some leeward features yesterday due to moderate Easterly winds in the Alpine. Triggering a wind slab will likely be shallow, but could step down to a deeper layer of the snowpack and create a much larger and more dangerous avalanche. 

Cornices: Cornices have grown and are suspect for breaking while traveling along ridgelines. Give these an extra wide berth and minimize any time below them. Cornice falls can trigger avalanches on slopes below.

Natural loose wet activity on Seattle Ridge in the afternoon yesterday. 


Mountain Weather

Yesterday was mostly cloudy in the morning and became mostly sunny by the mid to late afternoon. Temperatures were in the 20Fs to low 30Fs. Easterly winds were blowing 5-15 mph gusting into the 30s in the morning and calmed down in the afternoon. Overnight temperatures cooled slightly and then started rising in the early morning. Clouds moved in and Easterly winds were light. 

Today will be mostly cloudy with snow/rain showers, 1-4" of snow possible and rain below 800'. There is a chance of some clearing in the late afternoon. Temperatures will be in the high 20Fs to high 30Fs. Winds will be Easterly 5-15 mph with gusts into the 20s. It is forecast to be mostly cloudy overnight with a chance of snow showers. 

Tomorrow looks to mostly cloudy in the morning with clearing in the afternoon, light Northwest wind and temperatures in the high 20Fs to mid 30Fs. The next system moves into the area Thursday. Timing and details are still uncertain.

*Seattle Ridge anemometer (wind sensor) rimed over and not reporting

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  29 1    0.1 90 
Summit Lake (1400')   27   1    0.1 36 
Alyeska Mid (1700')  28  1    0.12 82 


RIDGETOP 24-hour data (6am - 6am)

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  20  ENE  14 38 
Seattle Ridge(2400')  23 n/a*   n/a* n/a* 

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).

Winter snowmachine use open/closed status and riding conditions updates

Riding status is not associated with avalanche danger. An area will be open to motorized use in accordance to the Forest Management Plan when snow coverage is adequate to protect underlying vegetation. Backcountry hazards including avalanche hazard are always present regardless of the open status of motorized use areas.

(Updated: Mar 15, 2018 )

Glacier District
Johnson Pass: Open
Placer River: OpenPlease avoid private property and AKRR job site at Luebner Lake. Cross railroad tracks if needed, do not ride down tracks, it is illegal.
Skookum Drainage: OpenCross railroad tracks if needed, do not ride down tracks, it is illegal. FYI, Skookum drainage closes to Snowmachines on 4/1 as per the Chugach NF plan.
Turnagain Pass: Open
Twentymile: OpenCross railroad tracks at designated spot as you leave the parking area.
Seward District
Carter Lake: Open
Lost Lake Trail: Open
Primrose Trail: Open
Resurrection Pass Trail: OpenResurrection Pass trail is open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Open
South Fork Snow River Corridor: Open
Summit Lake: Open

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The information in this advisory is from the U.S. Forest Service, which is solely responsible for its content. This advisory describes general avalanche conditions and local variations always occur. This advisory provided by the Chugach National Forest, in partnership with Friends of the Chugach National Forest Avalanche Information Center.

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