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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Graham Predeger  
Tuesday, February 2nd 2016
Created: Feb 2nd 6:25 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'
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The Bottom Line

Even though our snowpack is mostly stable in the Turnagain pass region, there are a few outliers that are keeping the danger at MODERATE today as both cornices and glide avalanches continue to act in unpredictable manners.  Fast moving, high volume sluffs and the potential for shallow, fresh wind slabs will also add to today’s concerns.

South of Turnagian Pass harbors a different snowpack structure where we found buried surface hoar responsible for a very large avalanche on Saturday in the Groundhog Creek drainage (Johnson Pass area).  If travelling in these areas recognize that we’ve got a persistent weak layer problem in addition to those listed below.


Primary Concern

It was impressive to stand on top of a ridge yesterday and look around at literally thousands of tracks littering the Turnagain pass area, and to know that is only a fraction of what was skied, hill-climbed and boot-packed last weekend.  Observations yesterday are pointing toward generally stable snow in the heart of the core area, with a couple of exceptions. 

Cornices are growing larger by the day and we have seen several fail naturally over the last few days. This is very indicative that many of these are reaching their tipping point and can fail naturally or be sped along by a skier or snowmachiners added weight.  With any luck these will fail mid-storm or overnight but often times it is a rise in temperature or direct sunlight that weakens the bonds and promotes failure.  Simply avoid time spent below cornices and when travelling along a corniced ridge, stay back much farther than you think necessary to maintain that added margin of safety. 

A cornice failure may cause a slab to pull out on the slope below, even in a relatively stable snowpack.  This appeared to be the case on Lipps, last Saturday.  

Large cornices hang over the SW Face of Magnum.  The horizontal track traversing below the cornice is an example of a very poor route decision.  The much safer option would have been to travel along the shaded ridge, well back from the edge.  photo credit: Josh Varney.


Secondary Concern

In sheltered terrain and mid-slope, where winds have not effected the surface, the snow continues to loosen and facet out.  Sluffs will be fast and have the potential to reach high volume in the alpine.  Don’t get caught off guard by this in steep, alpine terrain.  Getting taken out by your sluff can have very serious consequences in some of the complex and challenging terrain that we’ve seen people travelling to over the last several days.

WIND SLABS:

With 6-8” of loose, unconsolidated snow available for transport above ~2500’, shallow wind slabs could be quick to build and prove tender today.  Keep an eye out for active pluming off ridges as a sure sign of wind slab formation.  Expect any wind slabs forming today to be shallow (6-12”) but tender.

A few wind plumes yesterday were seen transporting the loose, surface snow into shallow wind slabs on Sunburst.


Additional Concern

The more you look around, the more glide cracks you see in Turnagain pass and surrounding areas.  Glide cracks continue to release here and there, without any real discernable pattern.  Best practice continues to be to limit your time spent exposed to glide cracks.  This takes some doing right now, considering the minefield of glide cracks that Turnagain pass currently is.

This glide crack on Cornbiscuit partially released sometime between Saturday afternoon and Sunday afternoon.


Mountain Weather

Yesterday proved to be quite a pleasant day in the backcountry with partly cloudy skies, temps in the low 20’s at ridgetops and winds in the low teens (mph) from the East. 

As fond memories of last weekend’s sunshine and exceptional snow fade into this workweek, we’ll usher in another period of unsettled weather beginning today and ramping up a bit tomorrow.  We can expect a few more clouds today along with an inch or two of snow above about 800’.  Temps are cool this morning but will be warming through the day and may reach the mid-30’s at 1,000’ by this afternoon.  Ridgetop winds are expected to be in the 15-30mph range from the East.

Tomorrow another front will begin to impact our area with potentially a bit stronger winds and more precipitation than what we see today.  

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  26  0  0 92 
Summit Lake (1400')  24  0  27
Alyeska Mid (1700')  28  0  70

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 19   ENE 11  34 
Seattle Ridge(2400')  22  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 25, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: OpenPlease park on road in and leave the turnaround (near outhouse) open for trailers to turn around.
Placer River: Open
Skookum Drainage: OpenSkookum drainage closes to motorized use on April 1 annually as per the Chugach National Forest Plan document.
Turnagain Pass: Open
Twentymile: Open
Seward District
Carter Lake: Open
Lost Lake Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Primrose Trail: OpenPlease STAY ON existing and hardened trail surface through the lower sections of this route.
Resurrection Pass Trail: ClosedClosed for 2016/17 winter season. This is a non-motorized season. This alternates every other year and will open again during the 2017/18 winter.
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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