Mon, January 14, 2013 Turnagain Pass Avalanche Forecast

Mon, January 14th, 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 greatest concern. This most recent load of snow, while dense, is probably not enough to drastically increase the likelihood of triggering these large and destructive avalanches. The weak layers formed in October and November are now buried 4-10 feet in many areas, and are getting more difficult to impact with the weight of a person or snowmachine.

Areas to avoid today are trigger points in upper elevation starting zones, where those weak layers are only covered by 1-3 feet of slab. If you’re able to hit one of these spots, the potential for avalanches to propagate across large areas remains very high. What this means is that the chances of starting one of these avalanches is low to moderate but the consequences are very high. Human triggered deep slab avalanches in the past two weeks have produced impressive amounts of debris, and still warrant our attention.

Avalanche Problem 2

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

With a gradual rise in temps over the past 2 days, we have an “upside down” scenario in the upper layers of the snowpack. Pit tests at treeline yesterday on Tincan revealed this weakness and showed potential for propagation across slopes. AKDOT was also able to trigger many avalanches around Bird Flats and Girdwood in the storm snow yesterday. While the storm snow totals were higher in these areas, the general trend of warming over the past 48 hours is similar in both places. Expect this problem to resolve itself more quickly than the deep slab problem.

Weather

Mon, January 14th, 2013

In the past 24 hours Turnagain pass has received ~8″ of new snow with .8″ water. Winds have been light to moderate out of the East averaging in the teens with gusts to 49 mph. Temps at 1800′ have been around 32 with temps at ridgetops in the mid twenties.
The biggest news in weather is that the forecasted rise in temperature and heavy precip did not come to fruition on Turnagain Pass. The Girdwood Valley has seen almost twice the amount of precip in the past 24 hrs.
Look for precip to taper off today and temps to start gradually dropping with freezing levels descending to sea level by tonight.
The extended outlook calls for a break in precip later today into Tuesday with snowfall returning by midweek. Temps will be significantly cooler through the next 3 days.

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Wendy will issue the next advisory tomorrow morning, January 15th.

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/25/22	Turnagain	Observation: Sunburst	Hannah Smith
11/25/22	Turnagain	Observation: Sunnyside / Seattle Ridge	Matti Silta
11/25/22	Turnagain	Observation: Sunburst	John Sykes
11/25/22	Turnagain	Observation: Tincan Trees	Andy Moderow
11/25/22	Turnagain	Observation: Tincan	Galen Hecht
11/25/22	Turnagain	Observation: Top of Seattle Ridge uptrack	Nick Crews
11/24/22	Turnagain	Avalanche: Sunnyside/Main Bowl	Andy Moderow
11/23/22	Turnagain	Avalanche: Seattle Ridge	John Sykes Forecaster
11/23/22	Turnagain	Observation: Tincan Trees	Brooke Edwards
11/23/22	Turnagain	Observation: Tin Can Common Bowl	Melanee Stiassny

Riding Areas

Updated Sat, November 26th, 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	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Placer River	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Skookum Drainage	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Turnagain Pass	Closed	The Forest has issued a closure order for Turnagain Pass due to inadequate snow cover for resource protection. Conditions will be monitored daily. Between 16-20” of snow exists at the parking lot. The scheduled opening would have been the Wednesday before Thanksgiving per Forest Plan.
Twentymile	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Seward District
Carter Lake	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Lost Lake Trail	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Primrose Trail	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
South Fork Snow River Corridor	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.
Summit Lake	Closed	Scheduled opening Dec 1st per Forest Plan, contingent upon adequate snow depth for forest resource protection.