Wed, March 13, 2013 Turnagain Pass Avalanche Forecast

Wed, March 13th, 2013

Alpine
Above 2,500'

Low (1)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

Low (1)

Alpine Above 2,500'		Low (1)
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

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

We’ve received a few more reports of impressive cornice falls, the exact timing of which is unknown. Without a trigger such as a person, dog, or snowmachine weighting the top of the cornice, failure is unlikely and very difficult to predict. Heat from the sun this afternoon does not look like a big factor today, but it is worth considering that they lose strength as the air temperature gets close to the melting point.

Avoiding unstable cornices is the key to staying safe around them. Try not to spend excessive time underneath them and know what is underneath you when traveling along ridges.

Check out Wendy’s writeup on the large cornice avalanche in Goldpan here.

Goldpan cornice avalanche

Avalanche Problem 2

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 slabs are possible in higher elevation terrain, and the surprise factor and ability to propagate across larger areas could make even shallow wind slabs dangerous in steep terrain. We got one report yesterday from the Portage valley area of a larger but shallow wind slab, the timing is unknown. Wind overnight briefly got strong enough to blow snow around. This concern should remain the exception rather than the rule.

Additional Concerns –

From what we saw yesterday, loose snow will move but I wouldn’t really call it a problem. In steep terrain our team could get the top 4 inches of snow to sluff easily, but volume was low and the moving snow stayed very manageable for a skier.

Wet snow sluffs are possible on south facing slopes late in the day. Again, everything we’ve seen qualifies as manageable, low volume, and slow moving. We have yet to see wet sluffs propagate into larger slab avalanches.

Weather

Wed, March 13th, 2013

Today looks like another day of perfect late winter weather. Sun is in the forecast, with increasing clouds this afternoon transitioning to snow tonight and tomorrow. Wind is light currently and should stay minimal throughout the day. Temperatures are relatively cold, but the sunny skies will help to make the afternoon comfortable and warm. This morning temperatures range from the mid teens in most areas to slightly below zero in the standard cold spots such as Summit Lake and Granite creek.

Tonight, snow is possible but the bulk of the precipitation looks to be in the daylight hours on Thursday.

Graham will issue the next advisory Thurday morning, March 14th.

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.