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Turnagain Pass Avalanche Forecast RSS

Archives
ARCHIVED FORECAST - All forecasts expire after 24 hours from the posting date/time.
Issued
Fri, March 22nd, 2013 - 7:00AM
Expires
Sat, March 23rd, 2013 - 7:00AM
Forecaster
John Fitzgerald
The Bottom Line

The avalanche hazard will increase to MODERATE this afternoon as new snow and wind build slabs above treeline.   These slabs will be sensitive to human triggers, especially in steep terrain. Below treeline the hazard will remain LOW where snowmachine and skier triggered avalanches are unlikely today.

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Fri, March 22nd, 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

New Wind Slabs

New snow and wind will work together to form wind slabs in the mountains today.  Do you remember what the snow surface looked like yesterday?  I do.  On south aspects (southern half of the compass) the surface was very firm and crusty.  Some areas on south facing slopes were holding a thin layer of loose snow. On north aspects (northern half of the compass) the surface snow was a wild mix of loose snow, firm crusts and slabs.  The overall surface pattern is what we call a potentially poor interface; faceted snow & crusts will behave as weak layers & bed surfaces respectively for avalanches today.  The question you will need to answer is: how big is this new slab?  The bigger the slab, the bigger your problem will be.  If precip totals trend toward the higher end, expect to see pockets of wind slab in the 12″ range today.

Old Wind Slabs
Yesterday my partners and I encountered older wind slabs that were formed by high winds earlier this week (Tuesday night).  Several parties have also reported triggering wind slabs up to 18″ in depth in the past two days.  These older slabs will be harder to trigger today but are worth avoiding, especially in steep terrain.

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

The most recent cornice fall observed in the region occurred in the last 2 days.  These backountry bombs have been dropping sporadically on their own over the past several weeks and have been large enough to do significant damage to a group of people.  New snow and wind will help to increase the sensitivity of aging cornices.  Avoidance is the only way to truly “manage” this type of problem.  Approach ridge crests with caution and don’t move out onto a ridge until you can see the snow below you.  Limiting your time below cornices will also help in avoiding this problem.

Weather
Fri, March 22nd, 2013

In the past 24 hours the mountains around Eastern Turnagain Arm have seen temperatures average 11 degrees F at the Seattle Ridge weather station (2,400′).   Winds at this site have averaged 12 mph out of the SE with gusts to 31 mph.   Precipitation has just begun this morning and stations are just beginning to report snow falling.

Today expect snowfall amounts to be in the 4″ to 8″ range, with greater amounts in the Girdwood, 20 mile and Placer Valleys.   Temperatures at 1,000′ will be in the mid twenties F and ridgetop winds will average 25mph out of the SW.

The extended outlook calls for an active weather pattern to bring more snowfall to the area through the weekend.

_______________________________________________________________________

Wendy will issue the next advisory tomorrow morning, March 23rd.

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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.