Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, December 19th 2013 7:00 am by Kevin Wright
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

Pockets of CONSIDERABLE avalanche danger may be found today.  Watch for areas with deeper storm snow and wind driven slabs.  Last night's storm is clearing today, but residual avalanche danger will linger as our weak base adjusts to the new load.  

During the fading daylight yesterday afternoon a couple small natural avalanches were noted along the Seward Highway.  This was at the very beginning of the stormy weather. 

 Show the Complete North American Avalanche Danger Scale
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.
Special Announcement

Join us tonight at Alaska Mining and Diving Supply for an Avalanche Safety Technology Workshop where we’ll be discussing and demoing some of the latest avalanche rescue technology including Avalanche Airbag packs and three antenna beacons.  As always, any CNFAIC workshop is FREE to the public!

Avalanche Problem 1

There was a lot of low density snow available for wind transport before this storm, and all the new storm snow came in cold.  Storm totals are in the range of 9-12 inches, with wind slabs probably reaching twice that depth.  Water content of the storm snow was around 0.6-0.9 inches (Snow Water Equivalent).

Wind was predominately from the East and Southeast at our Turnagain Pass ridgetop stations.  Expect the majority of wind loading to be on West aspects with crossloading on North and South.  

This cold storm should be compared to the one we got over the weekend.  In that storm we had a little more snow, but we saw a number of skier triggered avalanches.  We can expect the same today, with possible warning signs like whoomphing (collapsing) and shooting cracks.  Conservative decisions are justified today as the snowpack adjusts to the increased stress. 

Avalanche Problem 2

Storm slabs and wind slabs will be the evident surface layers, but the weak interfaces that may fail today could be older and deeper.  The freezing rain crust was one of the most reactive weak layers from last weekend.  It may show itself again today.  Below that rain crust we still have well developed facets on the ground.  Fortunately, digging a full depth pit to look at all those layers is easy with our shallow snowpack.  

Mountain Weather

Yesterday temperatures started a dramatic rise.  Portage had one weather station increase 56 degrees in the last 24 hours, from -25 F yesterday to 31 F this morning.  Ridgetop stations continue to read colder temperatures  - less that 20 degrees through the snowfall.

Snowfall and wind are the big news for us today.  Mid elevations in Girdwood and Turnagain Pass have about 9 inches of fresh snow overnight.  Wind was strong during the snowfall, reaching gusts to 64 mph on Sunburst and 56 mph on Seattle ridge.  

The blizzard warning for yesterday has expired, and the snowfall and wind are diminishing.  Some clearing this afternoon is expected.

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: Oct 05, 2019 )

Glacier District
Johnson Pass: ClosedClosed
Placer River: ClosedClosed
Skookum Drainage: ClosedClosed
Turnagain Pass: ClosedClosed
Twentymile: ClosedClosed
Seward District
Carter Lake: ClosedClosed
Lost Lake Trail: ClosedClosed
Primrose Trail: ClosedClosed
Resurrection Pass Trail: ClosedClosed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor: ClosedClosed
South Fork Snow River Corridor: ClosedClosed
Summit Lake: ClosedClosed

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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.

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