Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Sat, December 1st, 2012 - 7:00AM
Expires
Sun, December 2nd, 2012 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

ANNOUNCEMENT

Due to inadequate snow conditions and to prevent resource damage, operating or possessing a snowmobile on or within the Seward and Glacier Ranger Districts of the Chugach National Forest is prohibited until further notice.  You can view the official Forest Order for this closure HERE.


BOTTOM LINE

The entire shallow snowpack now consists of weak faceted forms, with surface hoar on top.  Stiffer slabs are becoming harder to find, and the avalanche danger is slowly diminishing.  Continue to be wary of pockets of stiffer snow in steep terrain above treeline where moderate avalanche danger can still be found.  

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Sat, December 1st, 2012
Alpine
Above 2,500'
Moderate (2)
Avalanche risk
Treeline
1,000'-2,500'
Low (1)
Avalanche risk
Below Treeline
Below 1,000'
Low (1)
Avalanche risk
Alpine
Above 2,500'
Avalanche risk
Moderate (2)
Treeline
1,000'-2,500'
Avalanche risk
Low (1)
Below Treeline
Below 1,000'
Avalanche risk
Low (1)
Danger Scale:
No Rating (0)
Low (1)
Moderate (2)
Considerable (3)
High (4)
Extreme (5)
Avalanche Problem 1
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

Pockets of unstable snow may still be present in wind loaded areas at high elevation.  Most slopes where people are skiing have weakened to the point where the entire snowpack is one big weak faceted layer.  This actually makes the backcountry safer now than it was a couple weeks ago, except that it’s easier to tag rocks on the way down…  

The analogy I’ve come up with compares the snowpack to engineering a building.  We all know that we can construct a tall stable skyscraper that can withstand significant stresses from wind and earthquakes.  The strength of that building relies fundamentally on the strength of the foundation.  If you build a skyscraper on top of a weak foundation, failure and catastrophic collapse is likely.  If you make a smaller and lighter building, the foundation doesn’t need to be as strong to support the structure above.  Our snowpack right now is a tent, without any foundation.  The tent itself is inherently weak, but collapse of that tent isn’t nearly as catastrophic as a collapse of the skyscraper.  In fact, the tent will bend when stressed before it breaks and collapses.  The big problem will happen when the next snow storm (new construction) gets placed on top of the tent.  How much weight can that tent support?

Why did the snowpack turn into one big weak layer?  Check out Wendy’s temperature profile graph HERE.  It’s all about weeks of high temperature gradients caused by shallow snow (only 22 inches in November) and cold air temperatures.

temperature gradient

Weather
Sat, December 1st, 2012

The forecasted high wind over the last couple days has not affected the Turnagain Pass region.  Clear, sunny, and cold weather will continue today and through the weekend.  A temperature inversion is still present, making higher elevations warmer than the valleys below.  Portage this morning is reading -18 degrees, while Sunburst at 3812 ft is reading 15 above.  

A pattern change is beginning to show up in the extended forecast.  A chance of snow is predicted for next 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 Sunday morning, December 2nd.

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Riding Areas
Updated Thu, April 01st, 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
Open
Please do not ride along Railroad tracks. Cross tracks at 90 degree angle and clear the right of way.
Seward District
Carter Lake
Open
Lost Lake Trail
Open
Primrose Trail
Open
Resurrection Pass Trail
Closed
Closed for the 2020/21 winter season.
Snug Harbor
Open
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.