Avalanche Advisory

Turnagain Area Avalanche Advisory
Friday, December 12th 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

The avalanche danger is LOW today across the forecast zone.  Our snowpack has had 3 days to adjust to the warm, wet storm earlier in the week.  Recent cooler temperatures have acted to lock the snowpack up tight at mid elevations around treeline. In the upper elevations (above ~2,500’) the snowpack is exhibiting good strength, low potential for avalanches to propagate and a good structure with the lack of a persistent weak layer. Human-triggered avalanches will be unlikely today though LOW danger does not mean NO danger. 

Concerns today will come in the form of all the other hazards associated with backcountry travel right now.  This includes cornices, glide cracks and early season hazards such as rocks, stumps, open water, etc.

Below treeline (1,500 and lower) there is not enough snow cover for avalanches to be of concern.

 Show the Complete North American Avalanche Danger Scale
1 Low Alpine / Above 2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
1 Low Treeline / 1,000'-2,500' Travel Advice: Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.
0 NO RATING Below Treeline / Below 1,000'
Special Announcement

Thanks to everyone who came out last night for the 2nd installment of our free Fireside Chat series!  We'll be back in Girdwood on Thursday December 18th for the next session covering the very important topic of human factors and decision making in the backcountry.  Check the calendar for more details and other up-coming events!

Avalanche Problem 1

Snow pit test results and some substantial slope testing are pointing toward a snowpack that is gaining strength and losing energy in the upper elevations as we put time between now and the (Dec. 7-9) warm storm of earlier this week.  Perhaps the most significant slope test in the backcountry yesterday was observed when a large cornice block failed unintentionally landing on a steep (~40 degree) slope pulling out only a small slab.  Without investigating fully, this is where I’d expect to find isolated pockets of stubborn wind slab in the 12" range.  If entering steep, committing terrain just below ridges today, practice safe travel protocol and good situational awareness identifying both safe zones and escape routes. An avalanche today is unlikely large enough to bury a person but moving snow could be enough to knock you off your skis or sweep you into a terrain trap.

We have observed widespread surface hoar growth throughout the Turnagain zone over the last 2 days.  Though not an issue today, this is sitting on a variety of surface types and could prove problematic if buried in-tact.  We'll be mapping this layer carefully with subsequent storms.

Early season hazards and a tenacious rain crust in the mid elevations (consistency of skiing over a coral reef) are legitimate concerns and require careful travel in order to avoid injury.  Boot-packing in the 1,000 – 1,500’ elevation band was by far the most hazardous part of our tour yesterday due to ice, early season hazards and a lack of snow.

Avalanche Problem 2

My partner and I witnessed 2 separate human triggered cornice failures in a matter of a half hour on the Tin Can ridge leading up to Hippy bowl yesterday.  Cornices in our region are fairly well developed for this early in the season.  Recognize them, and give them an extra WIDE BERTH if travelling on corniced ridges.  This holds true today and always!

                               2 separate cornice failures resulted from skiers traversing the ridge.  Hippy bowl on Tin Can.

Additional Concern

Being nearly impossible to predict or forecast glide avalanche failure, your best bet will be to simply avoid exposure to glide cracks entirely.  This avalanche concern is like a wild Horse; it has the ability to be tame through the entire season and melt out benignly or, release catastrophically without warning unleashing a fury of destruction.

Mountain Weather

The welcomed cooling trend continued yesterday across our region with all the weather stations (except Whittier) reading below freezing temperatures and dipping to the low 20’s F.  A lack of wind allowed a persistent fog bank to embed from the Anchorage bowl down Turnagain arm and south over Turnagain pass.  Just a trace of snow was observed on vehicles in Girdwood yesterday morning, really just precip particles associated with a low fog bank.  Above the fog (roughly 1,900’) the sky was blue, winds were calm and the atmosphere stable.

Weather looks to be quiet again today with weak surface flow likely not pushing the fog out of the region.  It’ll likely be another grey day at sea level but if you are fortunate enough to be in the mountains today, sunshine abounds above the low cloud deck!  We may see a small bump in temperatures to the high 20’s F at 1,000’ with ridgetop winds remaining in the single digits from the east.  No precipitation is expected today. 

Our next best chance for winter-ish weather appears to be tomorrow afternoon and into Sunday with a significant low tracking across the north Pacific today.  There appears to be plenty of moisture associated with this system and temps appear to be hovering right around the freezing mark.

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

  Temp Avg (F) Snow (in) Water (in) Snow Depth (in)
Center Ridge (1880') 21  .1   18
Summit Lake (1400')  19
Alyeska Mid (1700')  24  0 .1  11.8 


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

  Temp Avg (F) Wind Dir Wind Avg (mph) Wind Gust (mph)
Sunburst (3812')  21  W  5  13
Seattle Ridge(2400')  23 SE   3

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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