Tue, December 20, 2016 Turnagain Pass Avalanche Forecast

Tue, December 20th, 2016

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

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

A touchy snowpack was observed over the weekend as 12”-14” of new snow fell incrementally over a four-day period in Girdwood, Turnagain Pass and Summit Lake. This new snow arrived with moderate to strong Easterly ridgetop winds, which have redistributed the snow above treeline creating varying slab depths 1-2 feet thick. Several weak layers are sitting below this slab and are suspect right now in the alpine. A widespread layer of weak faceted snow remains our primary layer of concern and was the culprit in many skier triggered avalanches over the weekend. Yesterday an observation from Sunburst showed propagation potential on a layer of buried surface hoar (buried Dec.15th) which is sitting on a wind hardened bed surface along some ridgelines.

Approach your day with a cautious mind-set and be skeptical of all avalanche terrain (slopes steeper than 30 degrees) in the upper elevations. Obvious signs like cracking, wumpfing sounds, or recent avalanche activity are an immediate sign that the snow is unstable. However you may not see these signs until its too late, so remember our current poor snowpack structure is considered guilty until proven innocent. If you find yourself being tempted into bigger terrain this week keep your consiquences in mind:

Small terrain = small avalanches = relatively manageable
Larger terrain = larger avalanches = unmanageable

A handful of human triggered avalanches occured mid-storm on Sunday 12-18 on Tincan and Eddies. Slab depths are now thicker (12-20″) since the storm subsided and triggering this layer will take more force and could break unexpectedly once onto the slope.

If headed to Summit Lake on the Kenai natural avalanche activity and skier triggered avalanches were observed over the weekend. Check out this observation from Tenderfoot where touchy wind slabs are sitting on a very thin and weak foundation. Photo of Butch Mountain (SW aspect) taken on Dec.17 by Mike Ausman.

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

Expect cornices to be sensitive and easy to break off. They are also likely to trigger a slab avalanche below. If you choose to walk a ridgeline today, give these a wide berth and be aware of people below you

Additional Concern

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

“Sluff” may be fast moving on steep terrain features where the snow is loose and unconsolidated like in the trees. Be aware of terrain features that could have high consequence if knocked off your feet.

Weather

Tue, December 20th, 2016

Snow showers yesterday brought 1-2 € of new snow throughout the day. Easterly winds were light and temperatures averaged in the low to mid 20Fs. Overnight temperature dropped into the teens and winds were calm.

Today expect mostly cloudy skies and scattered snow showers. A chance of 1-3 € of snow is possible. Winds are expected to be light and temperatures in the mid to low 20F’s.

A clearing trend is in the forecast for the next few days bringing cooler temperatures (teens and single digits F) and the possibility of gap winds for the Eastern Kenai Mountains.

PRECIPITATION 24-hour data (6am – 6am)

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	25	1	.1	29
Summit Lake (1400′)	18	2	.2	9
Alyeska Mid (1700′)	27	trace	.08	19

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	20	ENE	4	19
Seattle Ridge (2400′)	23	ESE	3	9

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.