Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, February 12th 2015 7:00 am by John Fitzgerald
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is MODERATE in the Alpine and Treeline elevations.  Slabs up to 10” in depth could be triggered in steep terrain.  These slabs have the potential to run far on steep sustained slopes.  Wet loose avalanches will also be easy to trigger on steep slopes at all elevations today.

 Show the Complete North American Avalanche Danger Scale
2 Moderate Alpine / Above 2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
2 Moderate Treeline / 1,000'-2,500' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
0 NO RATING Below Treeline / Below 1,000'
Avalanche Problem 1

This week has brought much welcomed new snow to the area.  Snowfall amounts have been variable, with greatest amounts near Turnagain Arm and lesser amounts in the Girdwood Valley and as you head South along Turnagain Pass.  Winds have been in the moderate range.  What this leaves behind is a high degree of variability in the newest slab.

A layer of very weak snow below this slab is much more uniform throughout the forecast area.  A 3 week dry spell created this layer of mostly facets.  This layer is sitting on a stout crust in the lower and mid elevations.  

On Turnagain Pass you will encounter soft slabs 6-10” in depth depending on location.   Yesterday skiers remotely triggered slabs from up to 100 yards away.  Tests yesterday showed the potential for avalanches to propagate across slopes (see video below).

In the Girdwood Valley older wind slabs (4-8” thick) which formed almost a week ago sit on this weak layer.  These older wind slabs are concealed by 6” of storm snow.  This makes it more difficult to detect these slabs.

While slabs are not very thick, they do have the ability to connect across terrain features and produce enough volume to injure or bury a person.  This issue becomes more pronounced on broad, open and complex terrain.

What does this all boil down to?  Staying off of terrain over 35 degrees including slopes connected to steeper terrain will be the best way to avoid triggering slabs today.


Avalanche Problem 2

Warm temperatures, occasional sunshine and loose surface snow will combine to make wet loose avalanches another snowpack issue to manage today.  Avoiding steep sunlit slopes will be the best way to manage this concern.  While volume may be low initially, steep sustained slopes hold the potential to produce higher volume far running wet loose avalanches capable of carrying or injuring skiers and riders.  This issue becomes even more pronounced when terrain traps such as cliffs, gullies, glide cracks or trees are below.

Rollerballs and shallow wet loose avalanche activity on Lipps yesterday (Feb 11, 2015).  Expect more of the same today.

rollerballs on Lipps

Mountain Weather

Over the past 24 hours we have seen temperatures on the rise with ridgetop stations averaging in the mid to high 20s F.  Winds have kicked up on Seattle ridge into the 15 mph range in the early morning hours with other stations showing light winds.  A trace to an inch of snow fell on Turnagain Pass.

Today expect showery conditions, with periods of flurries and occasional clearing.  Snow accumulations will be light, in the 1-2” range.  Rain/snow line should hover around the 1000’ level.  Temps will remain mild as warm air pushes up from the South, keeping ridgetop temps in the high 20s to low 30s F range.  Winds will be out of the East at 10-15 mph.

The extended outlook is calling for continued unsettled weather.  A broad area of circulation around the Gulf of Alaska will deliver generally light precipitation and warm temps through the weekend.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 30 1 .1 36
Summit Lake (1400') 29 1 .1 9
Alyeska Mid (1700') 31 0 0 26


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 25 E 3 27
Seattle Ridge(2400') 26 N/A 11 30

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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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