Avalanche Advisory

Turnagain Area Avalanche Advisory
Saturday, December 12th 2015 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

CONSIDERABLE avalanche danger exists today above treeline.  An average of 12 to 24 inches of new snow since Thursday combined with moderate to strong winds in the alpine have created dangerous avalanche conditions.  Human-triggered avalanches 2-4’ deep will be likely in upper elevation, leeward terrain where fresh wind slabs sit on top of weak, faceted snow.  A rule of thumb for today is that you can expect the avalanche hazard to increase with elevation.

At and below treeline there is a MODERATE danger.  The new snow is showing signs of good bonding where it’s been unaffected by wind, though keep in mind we are still within 24 hours of the end of the storm and heightened avalanche conditions do exist on specific terrain features.

 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

The Chugach National Forest will open Turnagain Pass to motorized use TOMORROW, Sunday December 13th.  Scroll to the bottom of this page for more information on other riding areas in the Chugach National Forest.  If you head out, please ensure everyone in your group is carrying avalanche rescue gear and knows how to use it! 

Interested in how people make decisions in avalanche terrain? Montana State University's Snow and Avalanche Laboratory, is leading a project they hope will bring about a better understanding of those risk-taking decisions with a smartphone app.  Click here for more info, to participate and submit YOUR Alaska data to this international research project.  Snowmachiners, click here.

Avalanche Problem 1

New snow in quick storm bursts over the last 3-days have deposited from 4 to 24 inches of snow onto a layer of weak facets above 1,000’.  It appears that the northern section of Turnagain pass (Eddies, Tin Can, Main bowl and north) have seen the most snow with reports of 20”+ above 2200’.  Add to this winds in the 30’s and gusts in the 40’s and 50’s mph on Sunburst yesterday and we’ve got a recipe for tender windslabs in the 2-4’ range in the Alpine.  This problem is likely to be exacerbated the higher in elevation you go.  Make no mistake; this is not a ‘manageable’ avalanche problem for a skier.  Today would be a good day to seek out and jump on small (no consequence) test slopes keeping a keen eye for the classic red flags (recent avalanches, shooting cracks or whumphing).  If seen, recognize these as a sign to dial your terrain choices way back to seek out lower elevation, lower angle terrain.

With the predominant wind direction from the east and northeast, you can expect west and southwest slopes to be the most suspect for wind slab formation.  Unfortunately this includes much of the popular terrain in the Turnagain zone such as Eddie’s, Tin Can common bowl, CFR, Sunburst, etc.

Avalanche Problem 2

We can’t forget about the weak snow this latest series of storms now rests on.  Cold temps and clear skies last weekend produced a substantial and widespread layer of weak, faceted snow that now sits below 1-2’ of storm snow.  Yesterday’s storm prevented most people from getting into the alpine but observations at treeline show this interface to be bonding well.  I suspect with increased elevation (above 2500’), the weak layer/ storm snow interface could prove troublesome as these layers have a tendency to heal slower in colder temperatures.  There was a report of “a lot of localized whumphing and debris that only looked a day or so old” from Eddies yesterday, though we don’t have info in terms of aspect or elevation but it is suspect that the old snow/ new snow interface may be the culprit.

Again, look for red flags and scale back terrain choices if necessary.  Continue to practice safe travel techniques (ski one at a time and plan for your escape route/ safe zone) and be mindful of other groups in your vicinity while on slope or skin track.

Alders are feeling the weight of our most recent storms on the approach to Sunburst yesterday.

Mountain Weather

Yesterday we saw a short period of intense snowfall over eastern Turnagain arm with the northern side of Turnagain pass again being favored.  Areas such as Girdwood and Portage also saw snow to sea level.  Winds were predominantly from the east in the 20-30mph range, gusting into the 50’s on Sunburst. 

Today, the low pressure over southcentral breaks down and we may see a few lingering flurries but generally a clearing trend through tomorrow.  Temps will be in the mid to high 20’s F at 1000’ and low 20’s at ridgetops with light winds from the SE in the 5-15mph range.  The next front moves into our area late Sunday night/ Monday and brings with it another chance for unsettled weather during the work week.

For the weather geeks out there, take a look at this powerful Bering Sea storm currently impacting the western Aleutian Islands.  Looks like it’ll steer clear of our region but the NWS is saying “This storm will put itself in the top echelon of intense cyclones to impact the Bering Sea...." with a central pressure expected to bottom out in the 920's.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 27 4-6  .4  40 
Summit Lake (1400')  26  1  .1 13 
Alyeska Mid (1700')  28  5  .5 30 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  20 NE  22   53
Seattle Ridge(2400')  23 N/A  N/A  N/A 

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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