Mon, February 11, 2013 Turnagain Pass Avalanche Forecast

Mon, February 11th, 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

Sustained 40-60 mph winds on Saturday (two days ago) helped to form large dense wind slabs in many areas. Most of the new snow that fell over the weekend is well bonded to the old snow surfaces. In areas that received wind loading this bonding is not as good and it is easy to find “upside down” snow on ridgelines, in starting zones and above cross loaded gullies. While these slabs have been reluctant to move under the weight of a snowmachine or skier, they still warrant respect, as they are large in size and able to do damage to a person once released. Avoiding starting zones above 35 degrees, wind affected snow above terrain traps and isolated areas below treeline that have these slabs will be your best bet today.

Avalanche Problem 2

Cornice

Cornice

Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.

More info at Avalanche.org

The winds and snow that formed wind slabs over the weekend also helped to increase the size of cornices. Always give cornices a very wide berth. When approaching from below try to envision what would happen if that cornice you’re looking up at came towards you. When traveling above cornices in the higher elevations, always avoid the edge. If you can’t see what is below you or a cornice is looming above you it’s probably time to back off. Try to view cornices from the side to see where the ground is and where the snow is overhanging & unsupported. Heating from the sun combined with an absence of wind could increase the likelihood of cornices releasing today.

Additional Concerns

Loose Snow Avalanches

Several inches of light density snow will be found on the surface today. The potential for relatively small shallow loose snow avalanches exists. These will become a greater problem in steeper terrain. Avoiding these surface slides in steep terrain above cliff bands and gullies will help to minimize your exposure to this hazard.

Deep Slabs

We are still monitoring the weak snow at the base of the snowpack that formed in the first part of the season. Above 2,000 feet and in areas with less overall snow this problem is more pronounced. While it is unlikely to trigger a deep slab today, it can’t be ruled out. Assess the terrain you are on and ask yourself some questions. What is the overall snow depth? Are there potential trigger points where the snow is shallow? Continuing to follow good travel habits, i.e. only putting one person at a time on a slope and using true islands of safety will help to mimimize your exposure to this problem.

Weather

Mon, February 11th, 2013

The mountains around Turnagain Pass have picked up 2-4″ of new snow with .2-.3″ of water in the past 24 hours. The Girdwood Valley has had up to 6″ of new snow with .3-.6″ of water. Winds at 3,800′ have averaged in the high teens out of the E and SE and temperatures have been in the low 20s F.

Veering winds have slowed down this morning and temps are on the decline. Light snow is falling at sea level.

Snowfall will taper off this morning. Ridgetop winds will be light, blowing 10-15 mph out of the W and NW. Temperatures at 1,000′ will be around 30 degrees F and skies will be clearing through the morning hours.

The next chance for snow will come tonight and into tomorrow morning, with generally low amounts expected.

________________________________________________________

Graham will issue the next advisory tomorrow morning February 12th.

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.