Fri, March 01, 2013 Turnagain Pass Avalanche Forecast

Fri, March 1st, 2013

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Moderate (2)

Alpine Above 2,500'		Moderate (2)
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

Storm Slabs

Storm Slabs

Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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 recent storm had peak intensity 2 days ago, and dropped more than 2 feet of snow in some areas including Turnagain Pass. It was deep enough on Wednesday to make travel downhill quite difficult. After yesterday’s relatively clear weather that snow should be settled and consolidated to the point that travel is easier.

A handful of large avalanches were caused by that storm, including a large natural that crossed the Portage road. All the major avalanche programs in our region were doing explosive avalanche reduction work. After the storm ended yesterday, explosive triggers were only causing small to medium avalanches occasionally, with nothing deeper than the recent storm snow. The picture below shows one of the larger avalanches produced by Seward highway work yesterday.

Colder temperatures and calmer weather will be acting to bring stability to the recent storm snow, but it still deserves a cautious approach today.

Avalanche Problem 2

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 larger avalanches that we’ve seen this week are suspected to be a result of deeper weak layers at the late January crusts. The good news is it remains a less likely problem to encounter. The bad news is it remains a tough problem to predict and avoid 100% of the time, even for the experts.

The buried crusts can be found in some areas at mid elevations between roughly 1900 and 3000 feet. As those layers get deeper with each storm, the likely places to trigger deeper layers will be from shallow points that have been partially scoured by wind.

Weather

Fri, March 1st, 2013

Storm totals yesterday morning reached near 2 feet of snow and up to 2 inches of water equivalent in some areas. Areas such as Girdwood, Grandview, and Portage got more snow. Summit lake got less, but still enough to cause concern.

In the last 24 hours temperatures have cooled off a few degrees, wind has dropped, and precipitation ended by the afternoon.

Today, a weak low pressure is spinning in Prince William Sound which may bring a few inches of snow. Snowfall will end tonight and the weekend will bring a clearing trend. Expect temperatures in the 30s and light wind.

Fitz will issue the next advisory Saturday morning, March 2nd.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/28/22	Turnagain	Avalanche: Turnagain Pass – late May wet slab cycle	CNFAIC Staff
05/21/22	Turnagain	Avalanche: Magnum, Lipps and Tincan	CNFAIC Staff
05/17/22	Turnagain	Avalanche: Sunburst	CNFAIC Staff
05/17/22	Turnagain	Observation: Tincan Ridge	Joe Kurtak
05/11/22	Turnagain	Avalanche: Cornbiscuit and Magnum west faces	CNFAIC Staff Forecaster
05/07/22	Turnagain	Observation: Granddaddy	Kit Barton
04/29/22	Turnagain	Observation: Sunburst wx station	AS/ MM/ AM/ NH
04/28/22	Turnagain	Observation: More Turnagain Pass/Summit Lake wet slab activity	Alex Marienthal
04/27/22	Turnagain	Observation: Magnum	Sykes / Buttrick Forecaster
04/27/22	Turnagain	Observation: Girdwood/Summit/Turnagain Road obs	A S

Riding Areas

Updated Wed, June 01st, 2022

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 as of May 1 per Forest Plan.
Placer River	Closed	Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage	Closed	Closed as of April 1st per Forest Plan.
Turnagain Pass	Closed	Closed as of June 1st.
Twentymile	Closed	Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake	Closed	Closed as of May 1 per Forest Plan.
Lost Lake Trail	Closed	Closed as of May 1 per Forest Plan.
Primrose Trail	Closed	Closed as of May 1 per Forest Plan.
Resurrection Pass Trail	Closed	Closed as of May 1 per Forest Plan.
Snug Harbor	Closed	Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor	Closed	Closed as of May 1 per Forest Plan.
Summit Lake	Closed	Closed as of May 1 per Forest Plan.