Wed, January 02, 2013 Turnagain Pass Avalanche Forecast

Wed, January 2nd, 2013

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

Considerable (3)

Alpine Above 2,500'		Considerable (3)
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

This deep slab problem has already shown itself to be very active during the storm cycle. Now that the precip and wind has lessened, the likelihood of natural avalanche activity will decrease but human triggered avalanches will remain a serious problem. The longer we wait to jump onto steeper terrain, the less likely we will be to trigger a deep avalanche. As recently as yesterday we saw large avalanches triggered by the Department of Transportation. Since that time another 10 inches of snow has fallen in some areas. Some thoughts on the deep slab problem –

– whumpfing and shooting cracks may not be evident

– standard snowpit tests are not suitable for testing deeply buried weak layers

– a lack of observed avalanche activity is not a reliable indicator of potential hazard.

– Waiting 36-48 hours after significant weather changes will decrease the likelihood of triggering (but not eliminate it)

– In some places we have seen the same slope avalanche twice during the recent storm cycle

– Terrain management is the only reliable prevention tool when snow stability is a problem

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

Wind slab may be a problem above treeline today. We haven’t been able to see avalanche activity within the new storm layers because we haven’t been able to access higher elevation areas in the past 8 days. Recent wind and forecasted wind today may be loading up lee oriented slopes.

Weather

Wed, January 2nd, 2013

It’s been a wet and wild week, and it isn’t finished yet. The graphs below show Turnagain Pass snow depth and wind from the recent weather events.

snow graph

wind graph

Today’s weather looks to be mild by comparison. Snow showers are expected today, with 2-3 inches of accumulation. Rain line will be 500 feet. Southeast wind from 30-40mph during daylight hours. Increased precip and wind is expected again tonight. The overall weather pattern is expected to remain active, although not as intense for the remainder of the week.

John will issue the next advisory on Thursday, December 3rd.

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.