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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
Thu, March 21st, 2013 - 7:00AM
Expires
Fri, March 22nd, 2013 - 7:00AM
Forecaster
Kevin Wright
The Bottom Line

The danger rating is higher today, bumped to MODERATE above treeline for fresh reactive wind slabs found yesterday.   We had a number of reports of people finding stiff pockets that popped from the weight of a skier, in some cases causing the skier to go for a ride.  

Besides wind slab, cornices are still a problem and have produced the largest avalanche events we’ve seen the last week.   Loose snow is harder to find since the wind picked up, but some areas may still produce localized sluffing in steep terrain.

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Thu, March 21st, 2013
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
  • 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 wind picked up 2 nights ago with ridgetop stations reading sustained northwest wind to the 20s and gusts over 50mph in some places.  This was enough to produce specific areas of wind slab that can be triggered by a person.  Yesterday we found a small mid slope pocket that collapsed a ~30 foot section with shooting cracks within the 2-5 inch thick stiff wind slab.  Other people reported more serious occurances yesterday including one person who took a 250-300 foot ride. 

Keep in mind that this problem is confined to the surface, meaning it will not step down into deeper layers given the current stability of the snowpack.  However, in terrain with consequences it could be enough to be a hazard if caught off guard. 

Avalanche Problem 2
  • 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

With increased wind we also get increased stress placed on the cornices as they gain mass.  Below is a picture from the Summit Lake region that shows a good example of a large cornice failure.  Also note the pocket of wind slab to the right that doesn’t appear to be directly connected to the section of cornice failure. 

 

Weather
Thu, March 21st, 2013

Cold temperatures and clear skies continue this morning.   Wind has been moderate to strong for the past 36 hours from the northwest.  

Today is the last day of sun in the short-term forecast.   We can expect clouds to build throughout the day.   By tonight snow is back in the forecast, with 2-5 inches predicted.   The storm track is from the west, which is not the typical direction for Turnagain Arm to receive a lot of precipitation.   At this time the weather service is predicting more snow for the Matanuska and Susitna valleys.  

For long term stability, we can expect a dramatic decrease in stability with new snow in the forecast.   Our current snow surface is mostly near surface facets or sun crust, both of which do not allow for quick bonding of new snow.  


Fitz will issue the next advisory tomorrow morning, March 22nd.

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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
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Closed
Skookum Drainage
Closed
Turnagain Pass
Closed
Twentymile
Closed
Seward District
Carter Lake
Closed
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Closed
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Closed
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Snug Harbor
Closed
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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.