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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Monday, December 14th 2015
Created: Dec 14th 5:31 am
3 Considerable Alpine / Above 2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
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.
2 Moderate Below Treeline / Below 1,000' Travel Advice: Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.
 Show the Complete North American Avalanche Danger Scale
Special Announcement

Join CNFAIC forecasters for a Free Avalanche Rescue Workshop on Sunday, December 20th at Turnagain Pass!! This is a great opportunity to practice beacon searches, learn strategic shoveling techniques and more. This workshop is open to everyone and anyone, novices and experts. We will meet from 11:00-12:30 at the motorized parking lot. See you there!


The Bottom Line

Another round of snowfall with upwards of 6" overnight and strong wind is keeping the avalanche danger at CONSIDERABLE in the upper elevation start zones. Expect wind slab avalanches around a foot thick to be easily triggered on wind loaded slopes. A MODERATE danger exists below 2,500' for these same avalanches in areas the wind is affecting the snow. At all elevations, watch for loose snow avalanches on steep slopes.


Primary Concern

After a brief break in storms yesterday, another pulse of moisture added 5-6+" of new snow last night, with an additional 2-3" expected today. It's starting to look like winter up at the Pass! Yesterday also was the 1st time in over 18 months that enough snow covered the ground to allow the Chugach National Forest to open to motorized use. Many, many folks were out enjoying the day as well as testing the slope stability. After a good thumping by snowmachines, we only had one report of a sled triggered avalanche. This was remotely triggered in 2nd Bowl (Junior's Bowl). If anyone has additional information regarding any other avalanche activity please send us a quick note HERE.

Avalanche conditions today will be mainly confined to storm snow issues. These are:

WIND SLABS: Strong winds blew from a generally East direction last night accompanying the snowfall. With the new snow plus plenty existing snow available for transport, watch for any slope that has been freshly wind loaded. These slabs are likely to be around a foot thick, but do have the potential to 'step down' into deeper layers and trigger a larger avalanche. Watch for cracks that shoot from your snowmachine/skis/board and areas with a smooth rounded surface texture - these are signs that a wind slab is present and could slide if the slope is steep enough.

SLUFFS: Sluffs on steep slopes should be expected within today's light snow.

Again as Heather pointed out yesterday, the snowpack is dramatically thicker on the North end of the Turnagain Pass. With that said, the South side of the Pass is slowly filling in. Photo below is from Mike Records from the Silver Tip area:

 

The motorized lot on opening day 2015/16.


Secondary Concern

Under the 16-30" of storm snow from the past 5 days sits both a layer of Buried Surface Hoar (BSH) and a layer of Near Surface Facets (NSF). Although one of these layers may be the culprit for the avalanche yesterday, we cannot say that for certain since we were not able to investigate. We do know stability tests are showing mixed results, with the general theme of no reactivity. Although it is becoming unlikely to trigger a large avalanche breaking 2+' down, it is not out of the question and something to keep in the back of our heads.

A look at a layer of BSH at 3,100' on a SW aspect - you can see the 'thin gray' line in the middle of the snow (Photo credit Andy Moderow, report HERE). This layer is not found everywhere and since it can be a problem layer for avalanche activity, we are tracking it.
 


Mountain Weather

Yesterday afternoon skies clouded over, Easterly winds picked up and snow began to fall as a quick moving system rolled through. Between 5-6" of snow fell overnight with Easterly winds averaging in the 30's and 40's mph. Temperatures have climbed slightly and are sitting near 20F on the ridgetops and near 30F at sea level.

Today, intermittent snow showers will linger with mostly cloudy skies. We may pick up an additional 2-3" in favored areas. Winds have decreased this morning and will be in the 5-15mph range from the East.

Tuesday night through Thursday another round of snowfall is expected as a strong low-pressure moves into the gulf.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 23  0.4   41 
Summit Lake (1400') 21  0.2   14 
Alyeska Mid (1700') 24  0.42   35

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  17 NE  32  66 
Seattle Ridge(2400') 19  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 15, 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

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
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