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Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Thu, November 22nd, 2012 - 7:00AM
Expires
Fri, November 23rd, 2012 - 7:00AM
Forecaster
Kevin Wright
The Bottom Line

We are issuing advisories 5 days a week through November on Sat, Sun, Tue, Thur, Fri.

Bottom Line

Stronger wind overnight, combined with a serious weak layer and recent natural avalanche activity, will keep us at a CONSIDERABLE danger rating above treeline.  We are still finding frequent collapsing in undisturbed snow, which tells us the facets are still weak and ready to fail when stressed.  Any fresh windslab from overnight wind should be approached with a strong sense of caution.

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Thu, November 22nd, 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
  • 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

We found a big piece of the puzzle yesterday in the form of recent natural avalanches.  The presence of naturals underscores the seriousness of the current snowpack.  Sugary faceted snow crystals form the foundation of our snowpack everywhere right now.  They are showing a tendency to collapse when stressed and will avalanche on steeper slopes.  

Turnagain Pass got a small amount of snow on Sunday, which probably added enough stress to cause the avalanche in the picture below.  This is a steep north facing slope on Seattle ridge, and is representative of most of the region.  Similar problems have been found near Portage, Summit, and Eagle River.  

Natural avalanche in Warmup Bowl, north face.

The cold weather combined with such a shallow snowpack is transforming all the snow into weaker faceted crystals.  We are finding a strong temperature gradient everywhere which is made worse by sub-zero temperatures.  In most places you won’t find much of a stiffer slab on top of the weaker snow.  This lack of a slab is preventing a lot of slopes from avalanching for the time being.  When we do get stiffer snow and more stress on top of the delicate foundation, avalanches will be much more likely and dangerous.  

Avalanche Problem 2
  • 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

Wind overnight hit gusts to 30mph at ridge tops.  This is the strongest wind we’ve had in over a week.  If the wind was strong enough to transport the loose surface snow, we could have enough slab to cause problems.  Any stronger or denser snow on top of the super weak facets near the ground is likely to exacerbate our problems.  

Weather
Thu, November 22nd, 2012

Wind overnight is the big news since yesterday.  The last snowfall is now several days in the past, but was enough to cause some snow stability problems in the form of natural avalanches.  The storm hitting Southeast Alaska today is not expected to have a significant effect on Southcentral.  A slight chance of snow showers is possible today.  Wind is expected to increase in some areas this afternoon.  

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Riding Areas
Updated Mon, October 26th, 2020

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
Closed
Placer River
Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Twentymile
Closed
Seward District
Carter Lake
Closed
Lost Lake Trail
Closed
Primrose Trail
Closed
Resurrection Pass Trail
Closed
Snug Harbor
Closed
South Fork Snow River Corridor
Closed
Summit Lake
Closed

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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.