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Avalanche Advisory

Turnagain Area Avalanche Advisory
Sunday, March 4th 2018 5:32 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 1000’ on all aspects. Lingering wind slabs (up to a foot thick) will be possible to trigger along with a larger slab avalanche (up to 2' or more thick) that breaks in weak layers deeper in the snowpack. Sunshine today may trigger small wet loose avalanches on steep Southerly aspects. 

**If headed South of Turnagain Pass be aware of recent avalanche activity in Summit Lake and Lost Lake areas. Click HERE for the Summit Summary and click HERE for several observations from Lost Lake. 


 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

Elevated avalanche danger exists in many areas of Southcentral Alaska including Lost Lake on the Kenai, the Western ChugachHatcher Pass, and parts of the Alaska Range. Recent natural and human triggered avalanches have occurred this week due to new snow and strong winds region wide; more snow is expected in the Anchorage and Mat-Su areas this weekend.


Avalanche Problem 1

Persistent Slabs

Almost Certain
Very Likely
Likely
Possible
Unlikely

Chance

Historic
Very Large
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Size

Finding and triggering a slab avalanche that breaks in weak snow 1-2+' deep in the pack remains a concern. This could be in the form of a lingering wind slab or a much older slab that sits on weak layers in the mid-pack. Although today's clear skies should reveal a dusting of new snow from yesterday, this is likely only enough to obscure a generally variable and wind affected surface through the region. With a longer sunny day ahead, here are the things to keep in mind:

Lingering wind slabs:  Strong Northwest winds impacted the region last week and due to unusual wind loading patterns, formed hard wind slabs on a variety of aspects. Watch for steep areas harboring stiff snow over softer snow and cracks that shoot out from you. Old wind slabs can be found along ridgelines and in steep rocky terrain, but also mid-slope in cross-loaded gullies. Even a small slab can have high consequences in steep and committing terrain. 

Persistent slabs:  Several weak layers sit in the middle and base of the snowpack and as recent as last Tuesday, skiers triggered a large 'persistent slab' in the Summit Lake area. This problem has shown to be more pronounced on the Southern end of Turnagain Pass and Summit Lake where the snowpack is shallower (areas to the North, such as Crow Pass, could also be suspect). Wednesday, during the wind event, numerous large avalanches released naturally near Silvertip Creek and in Summit Lake, most likely due to winds overloading these various weak layers. In short, buried 1-2 feet deep are facets sitting on a crust at the mid-elevations and buried surface hoar at the higher elevationsWhumpfing has been widely reported in the mid elevation band region-wide. If headed out for a long day in the mountains, remember these layers are there and no red flags may be present before a slab releases. 

Solar warming/effects:  Sunshine today along with light winds may allow for enough warming to initiate small wet loose avalanches on steep Southerly aspects. Warming may also cause slabs to be more reactive; something to keep in mind as we choose our late afternoon terrain.  


A wide angle view of Sunburst, Magnum, Cornbiscuit and Lipps - it may be March, but a generally thin snow cover remains

 

Weak layers in the snowpack at the mid-elevations on the South end of Seattle Ridge

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Mountain Weather

Overcast skies and snow flurries were over the region yesterday, with a trace of snow accumulating. Temperatures were in the upper 20'sF at 1,000' and around 20F along ridgelines. Ridgetop winds were light and variable during the day before shifting Northwesterly overnight and picking up to the 5-10mph range. Temperatures also cooled to the teens overnight with colder air moving in.

Today, Sunday, we are expecting mostly sunny skies with light Northwest ridgetop winds (5-10mph). Temperatures are expected to rise to 30F at 1,000' and to the mid-20'sF along ridgelines. 

Tomorrow, Monday, clouds move back in with another chance for snow flurries (little accumulation). The big news is later this week, a larger low-pressure system is forecast to move into the Gulf of Alaska. This could bring a much better chance for snowfall to the Turnagain area and Western Prince William Sound. Stay tuned!

 

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 28  trace  68 
Summit Lake (1400') 18  28 
Alyeska Mid (1700') 23  trace   0.02 60 

 

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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812') 16   21
Seattle Ridge(2400') 20  NW    20 

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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