Mon, December 17, 2012 Turnagain Pass Avalanche Forecast

Mon, December 17th, 2012

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

Low (1)

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

Danger Scale:

No Rating (0)

Low (1)

Moderate (2)

Considerable (3)

High (4)

Extreme (5)

Avalanche Problem 1

Persistent Slabs

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

More info at Avalanche.org

The persistent weak layers that make up the lower half of our snowpack are becoming more stubborn to trigger but the very nature of these means they can persist long after any significant wind or precipitation. All it takes is the right trigger in the wrong spot to unleash a destructive slide. Keep this in mind as you travel through the mountains today and for the rest of the season, as this weak layer is widespread and likely to be with us for a while. Below treeline from the ground up, our snowpack is one persistent weak layer (buried surface hoar and facets of varying sizes). This does not pose a concern until we see significant wind or precipitation at these lower elevations to form an overlying slab.

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

This past weekend our snowpack has proven reactive to a skiers weight with several skier triggered wind slabs both on Tin Can and the SW aspect of Sunburst. These were all triggered between 2700-3000’ in wind-loaded terrain on west and southwest aspects. I don’t expect this slab to build much in the coming days given there is very little snow available for transport, but a skier or snowmachiner may still be able to trigger small avalanches in specific areas or large avalanches in isolated areas of big terrain. Continue to travel through the mountains with heightened concern today and do not disregard the red flags the mountains give us. Recent avalanches and loud whumphing are two you may expect to see today.

Weather

Mon, December 17th, 2012

Temperatures have begun to rise from yesterdays sub-zero lows but it’ll feel anything but warm in the backcountry today as you can expect a brisk north wind in the 17-35mph range for much of the day. Tomorrow looks to be our only chance to pick up a few flakes as winds become SE and a weak low pressure moves over Kodiak, but don’t expect much as the track appears to be well south of us. Looking out toward the weekend, models suggest a continuation of cold and dry conditions over southcentral Alaska… Don’t shoot the messenger!

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).

Wendy will issue the next advisory Tuesday morning, December 18th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/06/20	Turnagain	Avalanche: Pastoral Peak, north face	Andy Duenow
04/10/20	Turnagain	Avalanche: Wolverine	Mike Records
04/10/20	Turnagain	Observation: Eddies lookers right shoulder	Matt Yoder
04/09/20	Turnagain	Observation: Bench Peak	Mike Records
04/04/20	Turnagain	Observation: Tincan	Anonymous
04/04/20	Turnagain	Observation: Pete’s North	Anonymous
03/26/20	Turnagain	Avalanche: Tincan – Proper (SW facing)	CNFAIC Staff
03/26/20	Turnagain	Avalanche: Seattle Ridge	W Wagner Forecaster
03/25/20	Turnagain	Avalanche: Sunburst Uptrack @ 2000′	J. Boisvert
03/24/20	Turnagain	Observation: Turnagain – Road Observations	W Wagner Forecaster

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