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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Monday, April 6th 2015
Created: Apr 6th 6:06 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'
 Show the Complete North American Avalanche Danger Scale
The Bottom Line

The danger is MODERATE on steep slopes in the Alpine.  Fresh wind slabs 8-12” thick could be triggered on leeward slopes approaching 40º.  North facing slopes are also suspect and have dense slabs 2-3’ thick that could be triggered by skiers and riders.

The danger is LOW at Treeline where avalanches are unlikely.


Primary Concern

Winds will move around the 3-6” of loose snow that is currently sitting in the higher elevations.  Slabs will build as thick as 1 foot on leeward slopes in the Alpine.  With more snow available for transport in the Girdwood Valley expect slabs to be thicker there than on Turnagain Pass.  Another 2+” of snow falling today will help to slightly increase the size of wind slabs.  These slabs will be most sensitive as they are forming.  Be on the lookout for snow that is stiff, feels upside down or produces shooting cracks.  These slabs will exist in small pockets and will become more of an issue if triggered above terrain traps or on large steep (>40º) slopes.


Secondary Concern

Steep north facing slopes in the Alpine have a setup that hold the potential for large avalanches 2-3’ deep to release under the weight of a person or group.  This concern reared its ugly head last week and has since quieted down.  Despite the lack of activity on these deeper layers over the weekend, it is still worth keeping in mind that there exist pockets of dense slab sitting on layers of weak faceted snow. If you find yourself in steep North facing terrain make sure you take precautions to minimize your exposure - travel one at a time, identify escape routes and communicate your decisions and plans well within your group.


Additional Concern

If visibility improves enough for travel in the Alpine, expect terrain sheltered from the wind to have enough loose surface snow to produce low to medium volume sluffs.  This will be a minor issue, but like wind slabs will become more serious when travelling above terrain traps such as cliffs, gullies and trees.


Mountain Weather

Over the past 24 hours temps have remained mild with averages in the mid 20s F at ridgetops and low 40s F at sea level.  Precipitation in the form of snow fell yesterday morning with Girdwood Valley receiving 3” and Turnagain Pass picking up just a trace.  Winds were generally light but have picked up into the 20 mph range this morning at ridgetop level.

Today a mix of snow and rain will fall as a large and broad low pressure system moves in from the Bering Sea.  Accumulation will be light during the day with up to 2” expected.  Rain/snow line will be around 1,500’.  Ridgetop winds will be moderate, in the 15-25 mph range out of the East.  Temps will climb into the low 30s F at ridgetops.

The system responsible for stormy weather today will pick up in intensity tonight and into tomorrow.  Snow accumulation will be in the 8-10” range in the higher elevations by tomorrow morning.

Looking further out we can expect a continuation of unsettled weather through the middle part of the week with generally light precipitation through Wednesday.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 33 trace 0 58
Summit Lake (1400') 34 0 0 10
Alyeska Mid (1700') 33 3 .25 33

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 23 ENE 12 35
Seattle Ridge(2400') 25 n/a 17 39

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.


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
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