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ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Wed, March 6th, 2013 - 7:00AM
Expires
Thu, March 7th, 2013 - 7:00AM
Forecaster
Kevin Wright
The Bottom Line

In the absence of sun today, the danger will be generally LOW.   Warmer temperatures are expected for low elevations today, and combined with a small amount of rain we may see some minor wet loose activity below treeline.   Above treeline we are still finding a lot of mature overhanging cornices that can fail spontaneously at random times.   Overall our snowpack right now is strong, with only a couple weak anomalies that are very difficult to trigger by a person.  

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Wed, March 6th, 2013
Alpine
Above 2,500'
Low (1)
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
Low (1)
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
  • 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 throughout the region are getting to be very large in most areas, including Turnagain Pass.  The largest natural avalanches in the last 5 days have been as a result of cornice falls.  In Haines a heli-ski guide was killed over the weekend when his party collapsed a cornice.  We got a report of a natural avalanche in the Placer river region yesterday that may have been a cornice failure.

Cornice safety relies on managing exposure.  This means you should limit the time you spend directly underneath overhanging features, especially if temperatures are warm or they are in direct sun exposure.  Traveling directly on ridge tops can be safe, as long as you give a wide berth to any overhanging sections.  When standing on a ridge it can be very difficult to know how far back a cornice might break.  In general, the breaking point is much further back than you might expect. 

The good news related to cornices is that they are one of nature’s best slope stability tests.  We get a lot of information from cornice failures when the slope underneath gets pummeled by thousands of pounds of hard cornice chunks.  Based on our observations of cornice failure, the current snowpack is showing minimal reactivity to large triggers.  This means that backcountry travelers are unlikely to trigger a slab avalanche in the backcountry today.

The one recent exception was a cornice that triggered a deep slab on the mid elevation ice crust in steep terrain in the Girdwood valley on Sunday.

Avalanche Problem 2
  • Dry Loose
    Dry Loose
Dry Loose
Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
More info at Avalanche.org

Yesterday’s sunny skies were hammering southerly slopes with solar radiation.  Temperatures overall were not much above freezing, so the warming effect was minimal but still noticeable.  Some direct south facing slopes at low elevation showed a small amount of loose wet avalanche activity.

Sun is not in the weather forecast today, but temperatures are expected to reach into the low 40s at sea level.  This may be enough to melt the surface crusts and cause more minor loose avalanche activity by the afternoon. 

Weather
Wed, March 6th, 2013

Yesterday was sunny and calm with mild temperatures.   Our last big shot of moisture was 6 days ago, and the snowpack has been settling and strengthening since then.  

Today, rain and snow is in the forecast.   Actual amounts predicted are very minor, leading me to believe that new precipitation today will not have a significant effect on the avalanche danger.   The rain/snow line is predicted at 700 feet today.   Temperatures may reach into the low 40s at sea level.   Expect light wind to 15mph from the south.  

Tomorrow a larger storm system is moving into our region with high wind, rain, and snow forecasted.   We can expect the avalanche danger to increase for Thursday and Friday as a result of this coming storm.


Graham will issue the next advisory on Thursday, March 7th.

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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.