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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, December 10th, 2012 - 7:00AM
Expires
Tue, December 11th, 2012 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Above treeline, a CONSIDERABLE avalanche danger will linger today.   The 10+ inches of snow combined with high wind over the weekend built very touchy wind slabs on top of the super weak snow from November.   We found the wind slabs to be very reactive to human trigger yesterday with remote and sympathetic avalanches in numerous places.   This trend is likely to diminish slightly today, but conservative terrain management   will still be important.

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Mon, December 10th, 2012
Alpine
Above 2,500'
Considerable (3)
Avalanche risk
Treeline
1,000'-2,500'
Moderate (2)
Avalanche risk
Below Treeline
Below 1,000'
Moderate (2)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Considerable (3)
Treeline
1,000'-2,500'
Avalanche risk
Moderate (2)
Below Treeline
Below 1,000'
Avalanche risk
Moderate (2)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Wind Slabs
    Wind Slabs
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

The storm snow by itself didn’t seem to be creating very reactive or connected avalanches yesterday.  Adding wind loading to the mix built the stiffness and tension required to build a slab.  Wind loaded areas steeper than 35 degrees should be approached with caution today.  Any areas with this combination in high consequence terrain should be avoided completely.  Check out the observations from yesterday for some more examples of skier triggered wind slabs.

Likelihood – human triggered likely

Trend – decreasing since yesterday

Distribution – Widespread above treeline

Size – small to medium

Watch a video of the avalanche in the picture HERE.

Avalanche Problem 2
  • Storm Slabs
    Storm Slabs
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.
More info at Avalanche.org

Below treeline where wind did not affect the new snow, the snowpack behaves differently.  We found very little difference in density between the fresh light powder and the underlying weak facets.  However, I wouldn’t rule out the possibility of finding unstable storm snow below treeline.  If you find the right combination of an open steep slope at lower elevation, it may be able to avalanche as a slab or as a loose sluff.  This should be less dangerous than the wind slabs found up higher. 

Weather
Mon, December 10th, 2012

The storm Saturday to Sunday morning dropped about 10 inches across Turnagain Pass.   Winds were strong from the east, reaching gusts over 70mph.  

Today looks like calm weather that won’t contribute to avalanche problems.   A chance of snow is in the forecast with little accumulation.   Light wind and mild below freezing temperatures in the mountains.   The next chance of significant snow looks to be Wednesday.  


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).  

Wendy will issue the next advisory Tuesday morning, December 11th.

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Riding Areas
Updated Tue, April 20th, 2021

Status of riding areas across the Chugach NF is managed by the Glacier and Seward Ranger Districts, not avalanche center staff. Riding area information is posted as a public service to our users and updated based on snow depth and snow density to prevent resource damage at trailhead locations. Riding area questions contact: mailroom_r10_chugach@fs.fed.us

Area Status Weather & Riding Conditions
Glacier District
Johnson Pass
Open
No parking in turnaround at end of the road near the outhouse.
Placer River
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Skookum Drainage
Closed
The Skookum Valley is closed to snowmachines. This closure occurs annually on April 1 as per the CNF Forest Plan.
Turnagain Pass
Open
Twentymile
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Lost Lake Trail
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Primrose Trail
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Closed for the 2020/21 winter season.
Snug Harbor
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South Fork Snow River Corridor
Open
Summit Lake
Open

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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.