CNFAIC LogoCNFAIC Logo

Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Thursday, February 12th 2015
Created: Feb 12th 6:44 am
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'
 Show the Complete North American Avalanche Danger Scale
Alpine Air Alaska Inc
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.


Primary Concern

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.

 


Secondary Concern

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: May 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

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.


USFS SNOW AND AVALANCHE HOTLINE (907) 754-2369
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
© 2017 Chugach National Forest Avalanche Information Center. All rights reserved.
FCNFAIC