Sat, December 08, 2012 Turnagain Pass Avalanche Forecast

Sat, December 8th, 2012

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

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

Snowfall totals in the mountains are expected to be 10-18 inches today, with another 10-16 inches tonight. East wind at ridgetops will be 50-75mph. If this proves true, avalanche danger will reach HIGH sometime late today. Fresh snowfall and high wind will create wind slabs at upper elevations. The timing of the storm may catch people off guard as they try to use the Saturday opportunity before the accumulation gets too deep. With the blizzard warning in effect and a very weak base snowpack, it will not take a lot of snow for avalanche conditions to change quickly. Watch the changes as they happen today and be prepared to find a safe route back to the car before it gets too dangerous.

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

As the storm snow and wind slabs build, they will be resting on top of all the junky facets and surface hoar that built over the last month of cold dry weather. This is a really bad combination, and the first test in quite a long time. Everything about this setup is screaming bad news. All the new snow will fall on 2 feet of collapse-prone ball bearings. We can expect avalanches to behave more dangerously than normal, breaking at the new/old snow interface or at the ground and running far and fast. Propagation potential today will depend on the temperature of the storm (the density of the snow) and the intensity of the wind to build cohesive slabs. Even a small amount of cohesiveness in this new layer will allow for widespread connectivity of the slab.

If you can’t already tell, I’m pretty worried about the storm today!

Weather

Sat, December 8th, 2012

Yesterday was a cloudless and calm day in the mountains. This morning, temperatures have risen up to 10 degrees in some areas and wind is reaching into the 30s at the ridgetops. As of 6am snowfall has not started in Turnagain Pass or Girdwood, but radar in Prince William Sound is starting to show the precipitation approaching.

The blizzard warning is active across our region starting at 10am, so confidence in this storm is high. Expect snow – 10-18 inches today, and 10-16 inches tonight with 1.5 inches of water equivalent. East wind is expected to blow 50-75mph at the ridgetops. Temperatures will remain below freezing today, with slightly warmer temperatures tomorrow in coastal areas such as Seward and Whittier.

The weather that happens today will drive the overall avalanche danger. What you see is what you get, so pay attention if you want to play in the mountains today. New snow approaching 1 foot depth will take us into dangerous avalanche conditions where trying to outsmart the problem will become impossible.

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 Sunday morning, December 9th.

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 Sat, September 23rd, 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	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Placer River	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Skookum Drainage	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Turnagain Pass	Closed	Scheduled opening on the Wednesday before Thanksgiving per Chugach National Forest plan. Subject to adequate snow cover.
Twentymile	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Seward District
Carter Lake	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Lost Lake Trail	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Primrose Trail	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Resurrection Pass Trail	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Snug Harbor	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
South Fork Snow River Corridor	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.
Summit Lake	Closed	Scheduled opening per Chugach National Forest plan December 1. Subject to adequate snow cover.