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Avalanche Advisory

Turnagain Area Avalanche Advisory
Forecaster:   John Fitzgerald  
Friday, March 8th 2013
Created: Mar 8th 5:51 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

The avalanche hazard is CONSIDERABLE above treeline on wind loaded slopes and below cornices.  Natural avalanches are possible in the upper elevations, where expert travel skills are necessary today.  Below treeline the hazard is MODERATE where a new load of storm snow will be possible for a person or snowmachine to trigger.


Primary Concern

Strong winds accompanied with new snow have combined to create dense slabs 2-3' in depth in many areas.  With sustained winds averaging well over 30mph across the forecast area, expect to find wind slabs on a wide variety of aspects especially in the upper elevations.  Strong winds tend to deposit snow in the form of wind slabs further down slopes than normal.  While bonding of the new snow to the old snow is generally good, rapid loading caused by high winds is enough of a factor to create unstable conditions.  Pay attention to the makeup of the snow your are traveling on; if it feels punchy or sounds hollow and you're in steep terrain, back off. 

 

                                                 Additional Concerns

Storm Snow

Storm snow unaffected by wind will be more of a concern around the Girdwood Valley, where snowfall amounts are closer to a foot.  Less snow fell on Turnagain Pass and in the Placer Valley.  In general this storm started out windy and warm which allows for good bonding between the old snow surface and this newest slab.  Slopes with more than 10 inches of new snow should be treated as suspect today.

Persistent Slabs

Yesterday my partner and I found a weak layer of snow below a crust to be somewhat reactive in tests.  This interface was about 30" below the surface and could pose a problem at mid elevations.  This is not a widespread problem but is worth keeping in mind as new snow avalanches have some potential to step down to older buried weak layers. 


Secondary Concern

Cornices have gained in mass in the past 24 hours.  Natural cornice breaks are possible today.  Give cornices plenty of room today, as they will be very sensitive to human triggers.  Cornices have the potential to trigger slab avalanches after falling and impacting slopes.  We have seen cornices to be a problem lately during and after storms.


Mountain Weather

In the past 24 hours strong winds out of the East have averaged 43 mph with gusts as high as 110mph at the Sunburst station (3,880').  The peak intensity of winds occurred around 8pm last night.  Winds are still blowing in the 30mph range at ridgetops this morning, which is plenty of wind to transport snow.  Snowfall amounts have varied across the forecast zone with the Girdwood Valley picking up to 14" of new snow with 1.4" of water, Turnagain Pass getting 8" of snow with .6" of water and Grandview picking up a rain snow mix with a few inches of snow and .2" of water.  Freezing levels have hovered around the 500-1,000' level.

Today expect another 3-6" of new snow and winds to continue to blow in the 30 mph range out of the Southeast with gusts to 50mph. Temps at 1,000 will be around 33 degrees F.

Light snowfall will continue tonight and taper off by tomorrow.  Lingering clouds and precip will then stick around through tomorrow prior to high pressure setting in by Sunday.

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Kevin will issue the next advisory tomorrow morning, March 9th.

 

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

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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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