Fri, December 18, 2015 Turnagain Pass Avalanche Forecast

Fri, December 18th, 2015

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

Moderate (2)

Alpine Above 2,500'		Considerable (3)
Treeline 1,000'-2,500'		Considerable (3)
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

Dec.17 Storm Totals:
Turnagain Pass Center Ridge: 13”
Girdwood Midway: 5”
Summit Lake: 3”

Yesterday warming temperatures and sustained Northeast winds have left 1-2’ of upside down storm snow in Turnagain Pass. This snow proved tender yesterday and shooting cracks were observed above 2000’ in places where the snow felt stiffened by the wind. No avalanche activity was reported, but visibility was poor making it difficult to see if any natural avalanche activity occurred.

Today weather conditions will deteriorate again with the arrival of yet another storm that is expected to intensify this evening. Easterly winds will start building this morning along with snow showers by early afternoon. This weather will be adding stress to an already stressed out snowpack. Triggering a slab 2+’ deep will be more likely on unsupported terrain features like steep convex rolls, gullies, and above cliffs. Poor visibility is expected today, but should you choose to travel into the upper elevations, maintain a conservative Jedi mindset. Use stability tests like hand pits or ski pole tests to feel for upside down snow; denser snow sitting on weaker snow. Most of all don’t be tempted by the Dark Side (large open slopes.) Patience you must have!

Shooting cracks observed yesterday on Tincan and a 15″ slab failed easily above the skin track where snow was unsupported.

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

We have been tracking several layers of weak snow formed in early December that are now buried under 3-4’ of snow. Poor visibility and dangerous avalanche conditions have made it difficult to evaluate this problem in the upper elevations where a large trigger, like a snowmachine, could find a sweet spot. This is one of the those low likelihood/high consequence problems that is unlikely to occur naturally and is not manageable. This is one more reason to avoid large steep slopes until the snowpack can adjust to its new load.

Weather

Fri, December 18th, 2015

Yesterday a total of 13 € of new snow was recorded at the Turnagain Pass Center Ridge weather station. Sustained moderate winds from the Northeast became light yesterday, but not until most of the snow had already fallen. Temperatures warmed to above freezing, and rain/snow line reached 1200′ by mid afternoon.

Overnight no new precipitation was recorded, winds remained light, and temperatures cooled just below freezing (32F) at sea level.

Today Easterly winds are expected to start building this morning with the arrival of more snow. Snow showers will intensify by this evening and could bring another 1′ of new snow by tomorrow. Temperatures will be hovering around 32F making it possible for rain at sea level.

*Weather station data is taken from 6am yesterday to 6am today. Yesterday’s storm totals were calculated with the addition of yesterday wx station snow totals.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	30F	4	0.4	49
Summit Lake (1400′)	28F	1	0.1	17
Alyeska Mid (1700′)	31.5F	0	0.03	34

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24F	NE	11	36
Seattle Ridge (2400′)	27F	n/a	n/a	n/a

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 Mon, May 15th, 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	Open	Chugach NF staff will be assessing daily after May 15th. Please keep machines on the snow and avoid brown spots to keep this area open as long as possible.
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.