Sat, February 09, 2013 Turnagain Pass Avalanche Forecast

Sat, February 9th, 2013

Alpine
Above 2,500'

High (4)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

Considerable (3)

Alpine Above 2,500'		High (4)
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

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

The winds have begun cranking up into the 60 mph range this morning at ridgetops. Light density snow that fell two days ago combined with new snow will get blown around to form sensitive wind slabs today. Yesterday multiple parties reported seeing good bonding between the newest storm snow/wind slab and the old snow surfaces. The reactivity of the surface snow will increase today and will be most easily triggered as new slabs are forming. With potentially very rapid loading occurring today (50+ mph winds and up to 12″ of new snow forecasted), these slabs will be very sensitive to human triggers.

A general lack of persistent weak layers in the upper snowpack will focus my attention on the interface between yesterday’s snow surface and today’s new snow. The exception to this are very isolated pockets of surface hoar that were observed on Tuesday. With high winds expect loading to occur further downslope than normal as well as in the lower elevations.

Storm Snow

Below treeline an additional 6-8″ of new snow on its way will build slabs on a slick and hard crust that will be easy to trigger. While these storm snow slabs will be smaller than new wind slabs they are worth looking out for today. Watch for these slabs to be most easily triggered on steep rollovers in the lower elevations.

Be on the lookout for the most obvious signs of unstable snow: avalanches, shooting cracks and “whoompfing”/collapsing. If and when you are seeing these signs this is nature screaming in your ear, “Hey, it’s time to back off and turn around!”

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 problem has not shown itself in the form of an avalanche in almost a month. While this lack of activity is an encouraging sign, there is still weak snow at the base of the snowpack, primarily above 2,000′ in elevation. While the chance is remote for a deep slab avalanche to occur today, it is still worth remembering what is deep down in the snowpack. Relatively smaller avalanches initiated in the upper snowpack have the potential to step down in older layers of snow near the ground. This problem has a greater potential to show itself in areas of more shallow snow as evidenced here.

Weather

Sat, February 9th, 2013

A generally calm day in the mountains yesterday has given way to increasingly high winds this morning as a large and well organized low pressure center moves towards the region. Snow has begun to fall and ridgetop temps are currently in 20s F.

The NWS has issued the following warning:

…HIGH WIND WARNING REMAINS IN EFFECT UNTIL 4 PM AKST THIS
AFTERNOON FOR PORTAGE VALLEY AND TURNAGAIN ARM…

* LOCATION…PORTAGE VALLEY AND TURNAGAIN ARM.

* WIND…SOUTHEAST 45 TO 65 MPH WITH GUSTS TO 85 MPH.

* TIMING…STRONG WINDS WILL CONTINUE THROUGH EARLY THIS
AFTERNOON. WINDS WILL BEGIN TO DIMINISH LATE THIS AFTERNOON.

Wind will be the major player in creating dangerous avalanche conditions in the mountains today. New snow will play a close second in this equation. Snow fall amounts should be in the 6-12″ range and temps at 1,000′ will be in the low 30s F

Winds should back off slightly by this evening and snowfall should continue overnight and into Sunday.

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Wendy will issue the next advisory tomorrow morning February 10th.

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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.