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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
Sat, March 22nd, 2014 - 7:00AM
Expires
Sun, March 23rd, 2014 - 7:00AM
Forecaster
Kevin Wright
The Bottom Line

Confidence in the overall stability of our snowpack is increasing each day.  It has been a full week since the end of the last storm.  Since then we saw a typical rash of avalanches immediately following the storm.  The last few days people have really started skiing on steep terrain, without triggering the deep slab that has concerned us.      

Overall, we are starting to feel pretty good about our stability, but a twinge of doubt for the possibiltity of triggering a deep slab in steep complex terrain is preventing a low danger rating for now.  Our current stability is good, but it’s not as good as it can get.
 
A MODERATE danger can be found in some areas above treeline in steep terrain >35 degrees for deep persistent slab and wind slab.  Everywhere else the danger is  LOW.
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Sat, March 22nd, 2014
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
  • 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

This problem is increasingly becoming unlikely, but the hazard associated with it could be dangerous if triggered.  The storm snow from last week has now settled to about 3+ feet of hard consolidated snow.  This slab is strong and difficult to trigger, but it sits at an interface that sometimes shows poor bonding to the older layer below it.  

The deep slab is most likely to be triggered from a shallow area where the slab tapers down to 1 foot deep or less.  Alternatively a large trigger like multiple skiers or a snowmachine could initiate through a deeper portion of the slab.  

Photo – Typical steep terrain with deep slab avalanches evident from the storm and large cornice features.

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

We got a report of a small wind slab triggered in Pastoral a couple days ago.  Click here for observation.  An east wind was loading up westerly aspects.  Today it is possible to find stiff aging wind slab that could pop when traveled on.  Keep this in mind, especially in steeper terrain.

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 are big and mature this time of year.  As people get onto steeper terrain the cornice factor becomes more significant.  In some steep areas they are a mandatory nuisance to be negotiated.

Remember to scope out a safe entrance that avoids a blind approach onto overhanging cornice features.  Take a rope for a safe belay if you think your chosen line can’t avoid cornice exposure.  

Weather
Sat, March 22nd, 2014

The last storm ended more than a week ago.  High pressure and sunny skies have dominated the weather pattern since then.  We had some moderate wind on Thursday that blew some snow around.

We are looking at another calm sunny day ahead of us.  Temperatures will start out cold this morning, ~10 degrees at valley floor and ~20 degrees at the ridgetops.  The sun will quickly warm things up to the high 30s in the afternoon.  East wind to 10mph.

Sun will stay in the forecast into mid week.  No major storms are on the horizon as the Rex block continues to dominate weather over Alaska.

Observations
Recent Observations for Turnagain Pass
Date Region Location
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04/04/20 Turnagain Observation: Pete’s North
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03/25/20 Turnagain Avalanche: Sunburst Uptrack @ 2000′
03/24/20 Turnagain Observation: Turnagain – Road Observations
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.