Thu, January 10, 2013 Turnagain Pass Avalanche Forecast

Thu, January 10th, 2013

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Moderate (2)

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

Deep slab avalanches continue to be our biggest concern. The number of avalanches that are occurring is low, but the potential size and destructive force is very high. We received another wake up call on Tuesday, as a snowmachiner remotely triggered a very large avalanche on Seattle Ridge where amazingly no one was buried or injured. This avalanche had the potential to do a lot of damage. This is the second such event in the last week.

Clear skies yesterday gave us a chance to look around the Turnagain Pass area. We were able to see a lot of old crowns that have filled in as well as one recent natural avalanche above Seattle Creek that caught our attention. With forecasted weather not likely to change the overall hazard in the coming days, the potential for large destructive avalanches will remain.

Typically a person or snowmachine can affect a weak layer within a few feet of the surface. The new slab formed over the Christmas through New Years period is 6-10 feet in many areas. The most likely places to find a thin spot in the slab is above treeline where winds have created greater variation in slab depths.
Weak layers formed between October and December are widespread. It is safe to assume that almost anywhere you go in the mountains there is a weak layer somewhere below you. This thick slab/weak layer combo is what is allowing for these large avalanches to occur.

Traveling on lower angled slopes and avoiding large open terrain is your best bet for avoiding this unmanageable problem today.

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

Light to moderate winds have created small pockets of shallow new wind slab. Light density snow resting on the surface will get blown around easily today. The consequences of this problem increase in steep terrain and above terrain traps.

Weather

Thu, January 10th, 2013

In the past 24 hours temps have remained in the 20s F, winds have been light to moderate averaging in the teens/twenties out of the E and SE with gusts to 38mph. Light snow has begun to fall on Turnagain Pass and in the Girdwood Valley this morning.

In the mountains today we should expect to see light snowfall mainly in the morning with a few inches of accumulation possible. Ridgetop winds will be out of the SE averaging 15-20mph and temps at 1000′ will be in the mid 20s F.

The extended outlook calls for light precip each of the next 3 days with temps warming as a series of weak low pressure systems move through the area.

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Wendy will issue the next advisory tomorrow morning, January 11th.

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.