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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Saturday, February 28th 2015
Created: Feb 28th 5:36 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.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
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The Bottom Line

The avalanche danger is MODERATE in the Alpine today.  2’ slabs could be triggered in steep terrain.   These slabs have the potential to propagate across slopes and be large enough to carry, injure or bury a person.  

The danger is LOW at Treeline, where a crust caps the surface and avalanches are unlikely.


Primary Concern

A long dry spell back in late January created a layer of weak faceted snow that has now been buried by several storms.  These storms produced several slabs that now average 2 feet in thickness in the Alpine.  The combination of slab over weak layer can be found consistently above 2,500’.  The two areas that are most unstable are:

Steep terrain between 2,500-3,000’.  The slab/weak layer combo is sitting on a firm crust in this elevation band.  The slab is thinner in this lower half of the Alpine, making it easier to impact the weak layer.  Parties continue to report collapsing in this elevation band and test results point to continued unstable snow in this zone.

Steep terrain with a Southerly component.  A stout sun crust formed over 10 days ago in this terrain and has slabs in the 1 foot range sitting on it.  We have seen sporadic natural activity in this type of terrain recently and mainly on the periphery of the forecast area.

While it has been 7 days since the last loading event, the nature of a persistent weak layer is that is can remain active for a long time.  If you’re considering getting into committing terrain keep in mind that you may find the most unstable snow well below starting zones.  Because of this it will be important to pick lower angle terrain (35 degrees or less) and slopes that provide escape options along the way.


Secondary Concern

A few inches of new snow will fall by the evening hours in the higher elevations.  Very shallow slabs in the 6” range will form and be sensitive to human triggers in steep (40 degrees and over) terrain.  This is not a significant hazard but is worth keeping in mind if you are travelling above terrain traps such as cliffs, gullies, or trees.


Mountain Weather

The past 24 hours brought mild temperatures and increasing cloudiness to the area.  Winds were light out of the East and no new precipitation fell.

Today expect cloudy skies with light snow in the afternoon.  Snow accumulation will be light, in the 1-2” range.  Temperatures will be mild with ridgetops climbing into the high 20s F and a rain/snow line around 1,000’.  Ridgetop winds will be out of the East at 5-10 mph.

The thin band of moisture that will deliver a quick shot of snow will be replaced by high pressure by Sunday morning.  A large low pressure system will move across the Bering Sea and connect with a low in the North Pacific in the early part of next week, bringing the next chance for precipitation on Tues night.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33 0 0 40
Summit Lake (1400') 29 0 0 6
Alyeska Mid (1700') 27 0 0 23

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 30 E 7 26
Seattle Ridge(2400') 31 NW 13 28

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: Feb 22, 2015 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThe CNF is in a sad state of affairs this winter in terms of motorized use. A drive over Turnagain pass in late-February looks like the monsoon season of September/ October. Though unprecedented, Rangers have not given up hope yet on a snowmachine season.... Remember March 2014??? 5 feet of snow in 5 days! This is Alaska afterall!
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: Closed
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

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
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