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Turnagain Pass Avalanche Forecast RSS

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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Mon, February 17th, 2014 - 7:00AM
Expires
Tue, February 18th, 2014 - 7:00AM
Forecaster
John Fitzgerald
The Bottom Line

The avalanche hazard is CONSIDERABLE today above treeline.   Slabs up to 3′ in depth could be remotely triggered by humans in steep upper elevation terrain.

Below treeline the hazard is MODERATE.   It will be possible for people to trigger loose snow sluffs & isolated pockets of slabs up to a foot in depth in steep terrain in the lower elevations today.

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Mon, February 17th, 2014
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

The late January onslaught of rain and high temps was followed by a period of clear and cold weather.  At the tail end of this January storm a small amount of snow fell in the higher elevations.  That thin layer of snow sat on a stout slick crust for almost ten days.  During that time this layer grew weak.  Between Feb 7th and today over 36” of snow has fallen on top of this weak layer in the higher elevations.  In areas where this weak layer exists, mainly above 3,000’ and in some places above 2,000′, the potential for slabs up to 3’ in depth could release from the weight of a person.

This issue is a tricky one to detect.  Because the distribution of this weak layer is not uniform, it is difficult to know with confidence whether that weak layer is lurking below you or not.  It should be assumed that this combo is present above 3,000’.   This problem reared its ugly head yesterday with multiple parties reporting remotely triggered avalanches throughout the forecast area. Click for Eddie’s avalanche, Twin Peaks avalanche & Tenderfoot (Summit Lake area) avalanche.

Eddie's remote

The best way to manage this problem today is to simply avoid terrain over 35 degrees in the higher elevations.  You might be able to get away with skiing steeper terrain, but it is a roll of the dice given the current conditions.

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

Another modest batch of precipitation will refresh the riding conditions.  It will also require being on the lookout for issues related to storm snow instabilities.

Loose snow avalanches
These will be generally low volume but easy to trigger in terrain over 40 degrees.  This problem is one that becomes more serious when traveling above terrain traps such as trees, gullies and cliff bands.

Storm Slabs & Wind Slabs
It will be possible for humans to trigger newly formed slabs in steep terrain today.  Winds have been relatively light but enough to create new slabs up to a foot in depth.  Sticking to terrain 35 degrees and under, especially on leeward upper elevation slopes will be the best way to avoid this problem today.

Additional Concern
  • Cornice
    Cornice
Cornice
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
More info at Avalanche.org

Cornices continue to grow and build above many starting zones.  Give cornices a wide berth when traveling along ridge crests.  Pay attention to the terrain above you as well.  If you find your group below cornices spread out and only expose one person at a time.

Weather
Mon, February 17th, 2014

In the past 24 hours the mountains around Eastern Turnagain Arm have picked up ~5 € of new snow with ~.3 € of snow water equivalent.   Ridgetop winds have been out of the East at 12 mph with gusts to 38 mph.   Ridgetop temps have averaged in the single digits F and have been gradually climbing overnight into the low teens F.

Today expect snow showers to continue through the morning hours with potential for clearing skies by the afternoon.   Snow accumulations of 2-4 € are possible.   Winds will be light out of the East at 5-10 mph.   Temperatures at 1,000′ will climb into the high teens to low twenties F.

The massive upper level Low pressure system that has been parked over much of the state will continue to bring alternating bands of precip and clear skies until tomorrow.   That system will begin to break down beginning late tomorrow.   Expect more precip and rising temperatures as we head into the middle part of the week.

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Riding Areas
Updated Fri, May 01st, 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
Closed as of May 1. Thanks for a fun, safe season!
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.