Avalanche Advisory

Turnagain Area Avalanche Advisory
Wednesday, January 1st 2014 7:00 am by Graham Predeger
ARCHIVED ADVISORY - All advisories expire after 24 hours from the posting date/time.
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The Bottom Line

A warm winter storm overnight will ring in the New Year with CONSIDERABLE avalanche danger today where human triggered avalanches will be likely.  Wind slab and storm slab avalanches will be of great concern throughout the day as this new weight overloads buried weak layers.  Cautious route finding and conservative decision-making will be essential if travelling in avalanche terrain.  

 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.
3 Considerable Treeline / 1,000'-2,500' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
3 Considerable Below Treeline / Below 1,000' Travel Advice: Dangerous avalanche conditions. Careful snowpack evaluation, cautious routefinding and conservative decision-making essential.
Avalanche Problem 1

This latest storm to hit eastern Turnagain Arm is the first substantial shock to our snowpack this season.  With .9 inches of snow water equivalent (SWE) and 90+ mph gusts at ridge top weather stations in the Turnagain pass area, rapid loading will create dangerous avalanche conditions.  Above treeline, wind slab avalanches up to 3’ deep (unmanageable for a skier or snowmachiner) are likely to be triggered by a human today.  In areas below treeline there is some uncertainty as to how reactive this storm snow will be in areas protected from the wind.  Do not ignore obvious red flags today.  Recent avalanches, whoomphing of the snowpack and shooting cracks area all bulls eye clues of dangerous avalanche conditions!

                              Shooting cracks: An obvious red flag!

Of note, the Girdwood Valley looks to have received significantly more water weight that Turnagain Pass with Alyeska’s weather station (at 2800 feet) reading over 2” of water in the last 18 hours since the storm began.  


Avalanche Problem 2

Our snowpack to date is comprised of weak faceted snow above the ground, a series of crust/ facet combinations and a 12-20” slab that encompasses the entirety of December’s meager snowfall. This weak foundation of snow that has continued to prove reactive, just received a substantial shock with last nights storm over a short timeframe.  Like a hung-over NYE partygoer, the mountains will be grumpy and unstable today.  It is very likely that the December drizzle crust/ facet combination will either be overloaded by new snow and wind or, brought dangerously close to its tipping point today.  It will be wise to avoid avalanche terrain and let the mountains adjust accordingly over the next 24-36 hours.  

Mountain Weather

Don’t let the relative lack of weather in Anchorage fool you.  Yesterday was an active day in the eastern Turnagain Arm region.  Above freezing temperatures and rain at sea level transitioned to a rain/snow mix at 1,000 feet during the day light hours.  After dark Easterly winds began to pick up in earnest with the Sunburst weather station registering a 93mph gust at 6PM.  As of 6AM this morning we have about 8” of heavy, wet snow on the ground at Turnagain Pass.  This should bode well in weighting those pesky alder down!

Today we can expect continued unsettled weather as this latest storm dissipates.  Winds will be moderate out of the southeast and temperatures look to be similar to yesterday with rain at sea level, gradually cooling with elevation.  Another 2-8” of heavy, wet snow is expected above about 600’.

Some December stats below:

We end 2013 with a SWE that is only 20% of average for December.  With yesterday’s precip we narrowly missed the podium ending the month with 3.3” of water for the month, good enough for 4th place. Numbers below are from the Turnagain Pass SNOTEL Station (1880’).

Top 5 lowest December SWE from 1983 till 2013:

1st  1984 – 0.5”
2nd  2011 – 1.3”
3rd  1985 – 3.1”
4th  2013 – 3.3”
5th  2009 – 4.2”

Average December SWE is 16.2”

Snow Depth: 
Dec 31 2013 at midnight was 30”
Average for past 10 years is 64” (Data only goes back to 2004)

*The above numbers were calculated with SNOTEL data from the NRCS.

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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