Thu, January 03, 2013 Turnagain Pass Avalanche Forecast

Thu, January 3rd, 2013

Alpine
Above 2,500'

High (4)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

Considerable (3)

Alpine Above 2,500'		High (4)
Treeline 1,000'-2,500'		Considerable (3)
Below Treeline Below 1,000'		Considerable (3)

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 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 a skier on Tincan triggered a large avalanche and fortunately avoided burial. This was a very destructive avalanche, pulling out most of the snowpack on this slope. For info and photos of this avalanche click here, here and here. Stay tuned for more info on this avalanche.

During times of intense precip, like today, the likelihood of triggering deep slabs goes up. As storms subside the likelihood will go down. The high consequences, however, do not change.

The fact remains, and will remain for a long time, that weak layers near the ground are still weak. All it takes is finding a spot where the slab is less deep, i.e. where we can impact the layer more easily, and large destructive avalanches will occur. These trigger points are often very difficult to detect. The usual warning signs of recent avalanches, shooting cracks or whoompfing may not present themselves before it’s too late.

Observations from New Years Eve allowed us to see areas above treeline that have been greatly affected by high winds. Some areas have been scoured to the ground while other areas are holding massive slabs. With such a great variety of slab depths at the upper elevations, the potential to find a trigger point is now greater. The best way to manage this problem today is to avoid terrain that is steep enough to slide.

Avalanche Problem 2

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

With up to 10 inches of new snow and 50 mph winds forecasted, expect wind deposited new snow to be sensitive to human triggers today. The likelihood of getting wind slabs to release will be higher today than deep slabs. However, the potential for relatively shallow avalanches to step down into deeper layers make this a problem not to be trifled with. Below treeline and in sheltered areas, new storm snow unaffected by winds will also be a problem to look out for.

Weather

Thu, January 3rd, 2013

In the past 24 hours snowfall amounts have been in the 2-3″ range, ridgetop winds have averaged 35 mph out of the East and temps have remained mild, with freezing levels hovering around the 1000′ level.
Snowfall will pick up in intensity this morning and into the daytime hours, with total accumulations of up to 10″ possible during the day. Ridgetop winds will be 50-60 mph out of the SE, and temps at 1000′ will be in the low 30s F.
The general pattern of unsettled weather will continue through the weekend. Look for precip to continue and a gradual cooling trend to set up as we move into next week.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/22/23	Turnagain	Avalanche: Tincan	Nick D'Alessio
05/12/23	Turnagain	Avalanche: Tincan, Sunburst, Magnum, Cornbiscuit	Heather Thamm
05/07/23	Turnagain	Observation: Tincan – Bear Tracks	CNFAIC Staff
05/05/23	Turnagain	Observation: Seattle Ridge	AS/ WW Forecaster
05/02/23	Turnagain	Observation: Cornbiscuit	Schauer/ Sturgess Forecaster
05/02/23	Turnagain	Observation: Seward Hwy Turnagain Pass	Joel Curtis
04/30/23	Turnagain	Observation: Magnum	Ayla, Kit Crosby, Barton
04/29/23	Turnagain	Observation: Tincan	John Sykes
04/28/23	Turnagain	Avalanche: Taylor Pass/Pastoral	Schauer/ Creighton Forecaster
04/28/23	Turnagain	Avalanche: Tincan	Andy Moderow

Riding Areas

Updated Thu, June 01st, 2023

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	Closed May 15.
Placer River	Closed	Closed May 15.
Skookum Drainage	Closed	Will close to motorized use on April 1, 2023 per the National Forest Plan.
Turnagain Pass	Closed	Will close on June 1.
Twentymile	Closed	Scheduled closure May 1.
Seward District
Carter Lake	Closed	Scheduled closure May 1.
Lost Lake Trail	Closed	Scheduled closure May 1.
Primrose Trail	Closed	Scheduled closure May 1.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Closed	Extended opening until May 15.
South Fork Snow River Corridor	Closed	Scheduled closure May 1.
Summit Lake	Closed	Scheduled closure May 1.