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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, February 18th 2018 5:53 am by Wendy Wagner
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

The avalanche danger is MODERATE above 1,000' on all aspects. Human triggered slab avalanches 1-2' thick or more remain possible. These could be either shallow old wind slabs or larger slabs that break in old weak layers deeper in the snowpack. 

The Summit Lake area has seen more avalanche activity over the past week. Take a look at the Summit Summary HERE. 


 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.
Special Announcement

Hatcher Pass users - dangerous avalanche conditions exist in this area and several very close calls have occurred over the past few days. Please see the Hatcher Pass Avalanche Center forecast before heading that way.

Thank you to all the folks that joined CNFAIC yesterday for our 'beacon practice and avalanche rescue workshop' at Turnagain Pass! Plus, big thanks to AMDS for hosting and providing a post-workshop BBQ!

      


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Triggering a slab avalanche up to 2' or more remains our main concern for folks getting out into the backcountry on this nice holiday weekend. These slabs are becoming difficult to trigger as time passes, but the possibility for a large and unmanageable slide remains. The most likely place to find these are slopes that have not seen significant traffic this season. Several layers of buried surface hoar and weak faceted snow exist in the snowpack. Between 1 and 2' below the surface is the Jan 21 layer of buried surface hoar with weak facets directly below. This layer continues to show signs of reactivity. Yesterday a group in the Seattle Creek drainage (Main Bowl/1st Bowl area) reported widespread collapsing and cracking, presumably in the Jan 21st weak layer, at the mid-elevations.

Another thing to keep in mind is days are getting longer, allowing the sun to warm up Southerly slopes. Adding to this, a warm air mass moved in last night. These warmer temperatures can add to the instability of slabs that sit near the breaking point. The main point it, don't let the mountains lure you into thinking the snowpack is stable.


Avalanche Problem 2

Wind Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
Large
Small

Size

Lingering old wind slabs are scattered around the mountains. Although on the stubborn side, some of these slabs could still be triggered by a person. They are likely to be relatively hard and could break above you. The recent warm temperatures may also help to reactivate them. Watch for stiff snow over softer snow, pillowed surfaces and cracks in the snow that shoot out from you.

Wind slab avalanche, likely snowmachine triggered, from several days ago in 2nd Bowl in the Seattle Creek drainage.



Additional Concern

Deep Persistent Slabs

Above 3,000' in the Alpine, several old weak layers of facets and buried surface hoar sit near the ground and in the mid-pack. This structure is most pronounced in places with a thin overall snow cover, such as the South end of Turnagain Pass and the Summit Lake area.  As you plan your day, keep in mind that there are deeper persistent layers that could 'wake up' if you find a trigger spot in a shallow area. 


Mountain Weather

Mostly sunny skies with thin high clouds were over the region yesterday. Ridgetop winds were light and variable. Temperatures climbed at the upper elevations in the afternoon due to solar radiation along with a very warm air mass streaming in. Sunburst weather station at 3,812' reported 35F at 5pm and remains above 30F this morning. 

For today, partly cloudy skies are expected along with a chance for a few flurries this afternoon (trace accumulation possible). Ridgetop winds should increase slightly to ~5-10mph from the South and East. An inversion is in place this morning and temperatures in valley bottoms are between 5-15F, which are expected to increase to the low 30'sF through the day. Temperatures will remain warm at the mid to upper elevations.

For tomorrow, President's Day, a return to sunny skies and light winds are forecast. The middle of the week may see an increase in NW winds, yet the mostly clear skies should remain. 

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32  64 
Summit Lake (1400') 13  24 
Alyeska Mid (1700') 23  57 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 29  SW  19 
Seattle Ridge(2400') 29  16 

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
If you have comments or questions regarding CNFAIC operations or winter recreation management, please email staff@chugachavalanche.org
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