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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
Sun, March 16th, 2014 - 7:00AM
Expires
Mon, March 17th, 2014 - 7:00AM
Forecaster
Wendy Wagner
The Bottom Line

A CONSIDERABLE avalanche danger exists on all aspects and elevations 2,000′ and above. Slab avalanches 3-5′ deep remain possible for a person, group of people or snowmachine to trigger on slopes 35 degrees and steeper. These have the potential to be triggered remotely from ridgelines or the bottom of slopes. Additionally, watch for fresh wind slabs up to a foot deep on West, South and Northerly aspects as the Easterly winds pick up through the course of the day.

At elevations below 2,000′ there is a  MODERATE  danger where 2-5″ of loose snow sits on a snowpack composed of moist snow and crusts.

**These are dangerous avalanche conditions and sticking with conservative travel in avalanche terrain is recommended.  

Safer areas to recreate are in the flats and on slopes less than 35 degrees in steepness – or below 2,000′ and away from runout zones.

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Sun, March 16th, 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
  • Deep Persistent Slabs
    Deep Persistent Slabs
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
More info at Avalanche.org

Yesterday was a classic sunny Saturday after a storm cycle and many folks were out enjoying Winter Part III. Along with this were reports of a handful of large human triggered avalanches. Luckily, no one was reported caught as they were 3-5’+ deep, large and dangerous. Details are limited, but here is what we know:

–  Widow Maker Face (West facing, 2,500′ – Seattle Creek drainage). This avalanche was 5-6′ deep and likely remotely triggered from the ridgetop by a group of riders. More details HERE.

–  Four deep pockets in Tincan’s Hippy Bowl (Southwest facing, 3,500/3,000). These slides are suspected to have been remotely triggered from an adjacent sub-ridge. More details HERE.

–  Palmer Creek (South of Hope). At least one large snowmachine triggered avalanche was reported in this drainage – very little information at this time.

Photo below: Widow Maker avalanche – photo was taken by a person looking North on Seattle Ridge.

 

The avalanche activity noted above is suspected to be failing at the old snow/new snow interface. The new snow consists of the combined 3/10-3/14 storm snow that has settled into a very strong slab around 30″ to 4′ thick (thicker in wind loaded areas). The weak layer is suspected to be a thin 1-2cm layer of old weak snow and buried surface hoar sitting above the late February crust.

Lowering likelihood – high consequences:
The slab is thick enough that triggering the weak layer is difficult and the weak layer is showing signs of adjusting to the new load. However, this set up deserves our respect regardless. The sole reason is the sheer size and destructive power of a potential slide. 
If you haven’t noticed from the reports of yesterday’s activity, these are deep and dangerous avalanches – the kind that if you are caught up in, are likely not getting out of. Conservative terrain management is key once again for a safe day in the backcountry.

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

Ridgetop winds are forecast to pick up to ~20mph from the East by noon today and continue to increase into the 40-50mph range by tonight. Although only around an inch of new snow is expected this afternoon, there is upwards of 4-10″ of loose snow already on the surface available for the wind to transport. With these factors in mind, watch for winds to form slabs near ridgelines, on rollovers or by cross-loading in gullies. These slabs will likely be in the foot deep category and sensitive to human triggers.

Additionally, any wind loading and/or wind slabs triggered could stress buried weak layers and aid in triggering a deep slab.

Weather
Sun, March 16th, 2014

Yesterday was our first clear sky day since last Sunday; between Monday and Friday two storms rolled through bringing 4-5′ of dense snow to the Eastern Turnagain Arm mountains. During the past 24-hours temperatures have averaged in the teens from 1,000′ to 4,000′ and ridgetop winds have been light, 5-10mph, out of the East. Overnight, temperatures have dropped to the single digits above 1,000′ and clouds have begun to stream in.

Today, cloud cover and light snow showers will increase through the day due to a front sliding through from the West. Around an inch of snow is expected by this afternoon with another 3-5″ of low density snow possible overnight. Temperatures will remain plenty cold for snow to sea level – teens at 1,000′.  Winds from the East are slated to pick up this afternoon and by midnight blow in the 50mph range.

Tuesday, light snowfall is expected to continue with up to another 2-4″ accumulating. Winds look to remain strong from the East and temperatures cold enough for snow to sea level.

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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.