Avalanche Advisory

Turnagain Area Avalanche Advisory
Thursday, January 1st 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

The avalanche danger is MODERATE today at and above treeline.  Specific terrain features such as steep, unsupported slopes or cross-loaded gullies are the most likely areas to trigger a stubborn wind slab 2 feet or more in depth.  With persistent weak layers still present in the mid-pack, a wind slab today also holds the potential to step down into one of these layers and could conceivably propagate across steep terrain.

We are back to NO RATING below treeline (<1,000’) as there is not sufficient snow at this elevation band to warrant a danger rating.

 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.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

Happy 2015 from the entire Chugach National Forest Avalanche Center crew!!!  The Center has come a long way from its humble roots as a phone line and basic website in 2002 to what it is today.  We recognize our successes are a direct result of  an amazing community of skiers, sledders and businesses that support avalanche safety.  Furthermore, we owe much of our success and sustainability to the Board members that make up our Friends group, past and present.  Wishing everyone a safe, successful and happy New Year!

Avalanche Problem 1

Sunday afternoon through Tuesday evening brought a warm and windy storm to the core advisory area scouring many ridges of snow, and building dense wind slabs on leeward slopes.  With ridge top winds predominantly from the East, expect West-facing slopes, particularly in the alpine to have that dense, pillowy look, indicative of wind slab (see photo below).  The steeper the terrain today, the more likely you will be to find and trigger a wind slab.  Likely trigger points include areas where the slab thins or near rock outcroppings.  It’s important to keep in mind when dealing with this avalanche problem that wind slabs are notorious for luring skiers well onto a slope before failing, often times above a skier. 

At treeline elevations winds were quite erratic during this storm so expect wind slabs to have formed on a variety of aspects.  It’ll be time well spent today to seek out small test slopes (with zero consequences) on your skin up toward alpine and jump on these hollow-sounding slopes to see how the snow reacts to a skier’s weight.

All signs are pointing toward a storm layer that will stabilize relatively quickly but as always, it’ll be prudent to pay attention to any red flags the snowpack is giving us and practice safe travel protocol both on the ascent and decent today.

Notice the difference in texture between a wind-scoured ridge (safer travel option) and a wind-loaded slope where the slab exists.

Avalanche Problem 2

Though it’s been a full two weeks since we saw peak avalanche activity on a buried surface hoar layer in the Turnagain zone, it’s still proving reactive in snow pit tests.  This last storm added significant weight to these weak layers where wind slabs formed (though not uniform across the landscape), but judging by the lack of natural avalanche activity yesterday it doesn’t appear to have definitively tipped the stress vs. strength balance. Currently dormant in terms of avalanches, the nature of a persistent weak layer is such that it can return to a state of activity as more stress (weight) is added and thus we’ll continue to track and test these buried weaknesses as we ski into a new year.

Mountain Weather

Yesterday was a relatively mild day across the forecast area as the most recent storm ended rather quickly Tuesday night/ Wednesday morning.  Winds dropped off precipitously with a 24-hour average of only 5mph on Sunburst and temperatures hovering around the freezing mark at 1,000’ under mostly cloudy skies yesterday.  Turnagain pass saw just a trace of snow with a few lingering rain showers in the Girdwood Valley during the afternoon hours.

Today will mark the beginning of a pattern change in south-central Alaska as we transition into northern flow.  This boils down to clearing skies and temperatures slowly dropping throughout the day to the mid to high-20’s at 1,000’ before falling significantly overnight.  With this change in flow direction we can also expect a NW wind to kick up in the 18-33mph range at ridge top levels.   No snow accumulation is expected today or throughout the weekend as temperatures continue to drop.  By Saturday, high temperatures are only expected to reach the single digits under mostly sunny skies.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 32   Trace  .1  35
Summit Lake (1400') 30   0  7
Alyeska Mid (1700') 33   0  .01  26


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  26  variable  5 23 
Seattle Ridge(2400')  27  ESE  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, 2019 )

Glacier District
Johnson Pass: ClosedClosed as of 4.3.19
Placer River: ClosedClosed as of 3.20.19 due to lack of snow.
Skookum Drainage: ClosedPlacer access closed as of 3.20.19 due to lack of snow.
Turnagain Pass: ClosedClosed as of 5/6. Thanks for a great season all, see you next winter!
Twentymile: ClosedClosed as of 3.20.19 due to lack of snow.
Seward District
Carter Lake: Closed
Lost Lake Trail: ClosedClosed as of 3.22.19 due to lack of snow
Primrose Trail: ClosedClosed as of 4.3.19 due to lack of snow
Resurrection Pass Trail: ClosedClosed for the 2018/19 season. Next season will be open to motorized use.
Snug Harbor: ClosedClose as of 5.1.2019
South Fork Snow River Corridor: ClosedClosed as of 3.20.19 due to lack of snow.
Summit Lake: Closed

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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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