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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   Wendy Wagner  
Sunday, February 10th 2013
Created: Feb 10th 6:33 am
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.
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The Bottom Line

A CONSIDERABLE avalanche danger exists above treeline this morning as yesterday’s storm slowly exits the Eastern Turnagain Arm area. Triggering a wind slab avalanche 1-2+’ deep formed during very strong east wind over the past 36 hours is the main concern. Additionally, watch for looming cornices that could be teetering on the brink. Below treeline there is a MODERATE danger where warm temperatures may loosen the snow surface and wet loose and wet slab avalanches could be possible.


Primary Concern

Yesterday’s storm turned out to be a Girdwood Special with storm totals above treeline between 1-2’ while Turnagain Pass picked up only half that, 6-12” depending on elevation. A hand full of natural avalanches were seen and reported despite low visibility. These were above treeline and mostly garden variety wind slabs in the small to medium category. Seattle Ridge's cross-loaded gullies on the east face flushed out small slabs and sluffs but debris stopped before hitting the lower angle runnout zones. Below treeline no avalanche activity was seen as the new snow was quite warm and sticky.  Even though Summit Lake only squeaked out a few inches that area was still able to produce natural avalanches thanks to the strong NE winds.

Today, the strong east wind is on the decline but still blowing moderate which is enough to build slabs. Watch for these to be fairly touchy and just beginning the mending process. They most likely will be 1-2+ feet in depth and found off ridgelines, rollovers and cross-loaded in gullies and sub-ridges. If you see cracking in the snow around you it will be a bull's eye clue that slab is unstable. With the potential for lifting clouds and travel in the upper elevations, remember even a small avalanche triggered can be dangerous if one gets washed into a terrain trap (i.e., over a cliff or into a gully).

Below treeline:  There is between 5-10" of medium to dense powder on top of multiple crust layers. Yesterday the powder was sticking quite well to the crust, but if the dense snow becomes saturated today with rising temperatures and a creeping up of the rain/snow line, wet loose and wet slab avalanches will be possible above the crust.

Deep slab:  We are continuing to track the weak snow near the ground. This is buried 4-8’+ deep, gaining strength and not likely to be triggered by a person in many areas in the Turnagain Pass and Girdwood Valley. But that said, shallow areas remain in these regions and Summit Lake, being shallower in general,  harbors more of a concern. There are a couple great observations demonstrating these locations HERE and HERE.

 


Secondary Concern

With over 24 hours of warm temperatures, snow and strong east wind cornices continue to grow. A few of these broke off yesterday triggering shallow wind slabs below. Keeping an eye for what is above you and giving these guys a wide berth will be prudent as they could be close to the tipping point.


Mountain Weather

Obscured skies, snow and strong wind that dominated Saturday has persisted overnight. Sunburst weather station at 3,800’ recorded hourly averages in the 40’s and 50’s mph from the east with gusts in the 90’s. Storm totals (with a rain/snow line ~300’) from the past 36 hours, ending this morning at 6AM are:

Turnagain Pass (1880')       6" snow - 0.6" water eq.
Alyeska Mid (1700')          18" snow - 1.3" water eq.
Alyeska Top (2800')      18-24" snow - 2.2" water eq.
Summit Lake (1400')        2-3" snow - 0.2" water eq.

Today the strong east ridgetop winds will back down significantly to the 20-30mph range and shift to a more south and southwesterly direction. Snowfall should linger off and on adding around 1-3 additional inches. Temperatures are mild, 32 at 1000' and 23 at 3800', and should decrease slightly through the day.

Tomorrow we have a break in clouds and precipitation. Temperatures should cool off and skies clear. Could be a very nice day before another system looks to push clouds and flurries our way Tuesday/Wednesday.

 


 

Fitz will issue the next advisory tomorrow morning, February 11th.

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 16, 2017 )

AREA STATUS WEATHER AND RIDING CONDITIONS
Glacier District
Johnson Pass: Closed
Placer River: Closed
Skookum Drainage: Closed
Turnagain Pass: ClosedThanks all for a safe and fun season on the Chugach NF! Stay tuned for the 2017/18 season. #playsafe #snowtosealevel
Twentymile: Closed
Seward District
Carter Lake: Closed
Lost Lake Trail: Closed
Primrose Trail: Closed
Resurrection Pass Trail: ClosedResurrection Pass trail will be open to snowmachine use during the 2017/18 winter season.
Snug Harbor: Closed
South Fork Snow River Corridor: Closed
Summit Lake: Closed

Subscribe to the Turnagain Area Avalanche Advisory:

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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