Fri, March 08, 2013 Turnagain Pass Avalanche Forecast

Fri, March 8th, 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

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

Strong winds accompanied with new snow have combined to create dense slabs 2-3′ in depth in many areas. With sustained winds averaging well over 30mph across the forecast area, expect to find wind slabs on a wide variety of aspects especially in the upper elevations. Strong winds tend to deposit snow in the form of wind slabs further down slopes than normal. While bonding of the new snow to the old snow is generally good, rapid loading caused by high winds is enough of a factor to create unstable conditions. Pay attention to the makeup of the snow your are traveling on; if it feels punchy or sounds hollow and you’re in steep terrain, back off.

Additional Concerns

Storm Snow

Storm snow unaffected by wind will be more of a concern around the Girdwood Valley, where snowfall amounts are closer to a foot. Less snow fell on Turnagain Pass and in the Placer Valley. In general this storm started out windy and warm which allows for good bonding between the old snow surface and this newest slab. Slopes with more than 10 inches of new snow should be treated as suspect today.

Persistent Slabs

Yesterday my partner and I found a weak layer of snow below a crust to be somewhat reactive in tests. This interface was about 30″ below the surface and could pose a problem at mid elevations. This is not a widespread problem but is worth keeping in mind as new snow avalanches have some potential to step down to older buried weak layers.

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

Cornices have gained in mass in the past 24 hours. Natural cornice breaks are possible today. Give cornices plenty of room today, as they will be very sensitive to human triggers. Cornices have the potential to trigger slab avalanches after falling and impacting slopes. We have seen cornices to be a problem lately during and after storms.

Weather

Fri, March 8th, 2013

In the past 24 hours strong winds out of the East have averaged 43 mph with gusts as high as 110mph at the Sunburst station (3,880′). The peak intensity of winds occurred around 8pm last night. Winds are still blowing in the 30mph range at ridgetops this morning, which is plenty of wind to transport snow. Snowfall amounts have varied across the forecast zone with the Girdwood Valley picking up to 14″ of new snow with 1.4″ of water, Turnagain Pass getting 8″ of snow with .6″ of water and Grandview picking up a rain snow mix with a few inches of snow and .2″ of water. Freezing levels have hovered around the 500-1,000′ level.

Today expect another 3-6″ of new snow and winds to continue to blow in the 30 mph range out of the Southeast with gusts to 50mph. Temps at 1,000 will be around 33 degrees F.

Light snowfall will continue tonight and taper off by tomorrow. Lingering clouds and precip will then stick around through tomorrow prior to high pressure setting in by Sunday.

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Kevin will issue the next advisory tomorrow morning, March 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 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.