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Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 31st 2018 4:26 am by Aleph Johnston-Bloom
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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BROUGHT TO YOU BY
The Bottom Line

The avalanche danger remains MODERATE above 1,000' for triggering a slab avalanche 1-3' thick. Slopes with signs of wind loading will be the most suspect for triggering an avalanche. Additionally, watch for easily initiated loose snow avalanches (sluffs) on steep slopes. 

 


 Show the Complete North American Avalanche Danger Scale
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.
1 Low Below Treeline / Below 1,000' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

There were a couple reports of people triggering small slabs on wind-loaded slopes yesterday, one skier and one snowmachiner. The 1-2' of snow that fell at the end of last week loaded a layer of widespread surface hoar, that was buried on January 21st. There were a number of human triggered avalanches over the weekend but overall the storm snow has only been acting as a slab in areas that were affected by wind. This continues to be the case.  The slides yesterday occurred in the Johnson Pass area and on Eddies.  One group investigated and found that the weak layer in the slide they triggered was the January 21st buried surface hoar underneath wind-affected slab.  This is a good reminder that despite the cold and clear weather now slowly faceting away the slabs; there is still the possibility of finding and triggering lingering slabs in leeward terrain today.  Remember that the surface hoar is lurking underneath the recent snow and it's important to assess areas affected by wind. Slabs can be deeper in loaded areas. Pay attention to slopes where the snow feels stiff, looks pillowed or sounds hollow and watch for shooting cracks. A small slab in the wrong terrain could have high consequences. 

Small slab in the Johnson Pass area, intentionally triggered in a 'sled cut' yesterday. 

It is important to keep this snowpack structure in mind today on slopes with wind-affected snow. Buried surface hoar could be underneath. 

These avalanches occurred on Eddies Saturday and were remote triggered from the ridge. They were noted again yesterday by a party in the area that had a ski cut produce a slab, 16" deep and 30' wide in similar terrain, that ran to the bench below. Photo: Joe Engel

 


Avalanche Problem 2

Dry Loose

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

As the cold weather continues to loosen and facet the surface snow, loose snow avalanches (sluffs) are becoming larger and faster by the day. Watch out for and manage your sluff in steep terrain features protected from wind.


Additional Concern

Deep Persistent Slabs

Triggering a deep slab is becoming unlikely, but is still not out of the question above 3000'. In the high elevation snowpack there are a variety of weak layers in the mid pack and near the ground. Because of this poor structure, there is still a chance of triggering a deep slab if you find the wrong spot. The most likely trigger spots are in thin areas in the snow cover, often near rocks, or where the slope rolls over. 

 


Mountain Weather

Yesterday was clear and sunny. Temperatures were in the single digits to mid teens. Winds were easterly and picked up a little in the afternoon gusting as high as 20 mph. Overnight the skies became partly cloudy. 

Today skies will be mostly to partly cloudy. Winds are forecast to be calm and temperatures will be in the mid to high teens. Skies will become clear again overnight. 

This weather pattern will persist into the weekend with more sunshine, cold temperatures and calm winds. From the NWS, the "blocky" pattern aloft maintains it`s hold over the regional weather pattern. There is still discussion of a pattern shift but a lot of uncertainty about timing and how much it will impact this region. 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880')  14  0  0  65
Summit Lake (1400')  4  0  0  18 
Alyeska Mid (1700')  10  0  0  52 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') NE   8 20 
Seattle Ridge(2400')  11  ESE  9 19 

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 06, 2018 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: ClosedClosed as of April 20th
Placer River: ClosedClosed as of April 17th
Skookum Drainage: ClosedClosed as of April 1st.
Turnagain Pass: ClosedClosed as of May 7th. Happy summer, see ya when the snow flies!
Twentymile: ClosedClosed as of April 13th
Seward District
Carter Lake: ClosedClosed as of 4/27
Lost Lake Trail: ClosedClosed as of April 13th
Primrose Trail: ClosedClosed as of April 13th
Resurrection Pass Trail: ClosedClosed as of April 20th
Snug Harbor: ClosedClosed as of 4/27
South Fork Snow River Corridor: ClosedClosed as of April 13th
Summit Lake: ClosedClosed as of April 20th

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
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