Sat, January 26, 2013 Turnagain Pass Avalanche Forecast

Sat, January 26th, 2013

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

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

The last couple days have brought steady stiff wind, and combined with light snowfall it has created a subtle stiffer layer of snow on multiple aspects. Yesterday we took a closer look at a couple small windslabs on the south side of Tincan. The small, isolated windslabs were becoming less likely to trigger. There is no persistent weak layer associated, but the subtle structure differences in the layering are just enough to make it break at an interface 1 foot deep.

This kind of windslab is manageable in the right terrain. It should be expected near ridges, under cornices, and may be easy to trigger the small low volume pockets. The manageability of this problem is directly related to the terrain. If you get surprised in steep, high commitment terrain it could very well be dangerous.

Cornices are building and may be unstable. One of the small slabs at Tincan was triggered by a naturally failing cornice. We can expect other cornices around the region to be large and easy to collapse under the weight of a person, snowmachine, or dog.

Avalanche Problem 2

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

The deep slab is getting to be less of a problem. However, the high consequence of a large deep slab avalanche is still affecting my own travel decisions despite the low probability of triggering one at this time. Causing one today will require the right combination of a steep slope and shallow trigger point.

Weather

Sat, January 26th, 2013

Temperatures have dropped dramatically over the last 2 days, and despite sunny weather today, it’s going to be a cold one. The highest temperature we see this morning is 10 degrees in Portage and it drops as you get to higher elevations. Above 3000 feet is negative temperatures.

Wind has been strong and steady at the ridgetops and in Turnagain Arm recently, a trend which will continue today. The wind chill factor up high will be quite cold. We can expect snow plumes blowing off the mountains, building windslabs and creating cornices. Some areas will see a strong northwest wind through channeled terrain.

Below treeline the combination of recent thawing temperatures and the deep freeze yesterday has created a solid supportable crust from 0-1500 feet elevation. There is good skate skiing potential on the crust today around Turnagain Pass.

Wendy will issue the next advisory Sunday morning, January 26th.

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 Mon, October 26th, 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
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