Sun, December 03, 2017 Turnagain Pass Avalanche Forecast

Sun, December 3rd, 2017

Alpine
Above 2,500'

High (4)

Treeline
1,000'-2,500'

High (4)

Below Treeline
Below 1,000'

Considerable (3)

Alpine Above 2,500'		High (4)
Treeline 1,000'-2,500'		High (4)
Below Treeline Below 1,000'		Considerable (3)

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

The first significant storm of the season is on the doorstep this morning, and it’s a warm one. Temperatures have begun to climb and winds are picking up from the East. A moisture laden band of snow is on the way from the Gulf and between 10 – 20″ of snow is expected today with another 10 – 20″ tonight above 1,000′. This is just what the snowpack needs – a big warm storm to hopefully stomp out the shallow, weak and precarious existing snowpack. Not only will this ‘rapid loading’ event be enough to create natural avalanches in itself, the loading will occur on a VERY weak snowpack making it that much easier for avalanches to release.

Again, travel in avalanche terrain during this storm is NOT recommended – in fact, today is a great day for Christmas shopping!

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During the past several days we have seen widespread human triggered avalanches due to our current snowpack structure. The set up is relatively simple, a slab averaging 12 – 20″ thick is sitting precariously on a layer of weak facets. Skiers have been able to trigger multiple avalanches from ridges and areas hundreds of feet away – this is how touchy we are talking. With a new load of snow on the way piling up on the existing slab, we can expect the balance to be tipped and widespread natural avalanches breaking near the ground.

Pre-storm snowpack structure from Sunburst at Turnagain Pass:

Tincan Common on Dec 1st – Skiers along looker’s right hand ridge, out of view, remotely triggered these three pockets while descending (Victoria Lytle photo)

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Weather

Sun, December 3rd, 2017

Yesterday, the mountains saw mostly overcast skies and light snow showers. Turnagain Pass picked up 1″ of snow in the past 24 hours and the upper elevations of Girdwood 2-4″. Winds during this time were 10-15mph gusting in the 30’s and temperatures in the mid 20’s F at treeline and the low 30’s at sea level.

Today, expect a potent storm day. Around 1+” of rain is expected to fall below 1,000′ and possibly 1,500′, this translates to 10 – 20″ of snow at the higher elevations. Tonight we could see another 1+” of rain and another 10 – 20″ of snow. Winds will be Easterly in the 30-50mph range with gusts to 80mph or more. Temperatures should climb to 30F on the 3,500′ ridgelines and 40F at sea level.

Monday, snowfall should taper off and temperatures cool slightly as the storm moves out. We may get a slight bit of visibility Monday afternoon before another front pushes in and a chance for additional snow on Tuesday. This week will be quite active weather wise. Stay tuned!

*Center Ridge SNOTEL is reporting erroneous temperature data. See Turnagain Pass DOT weather station for accurate temperature at 1000′.

**Seattle Ridge weather station anemometer is covered with rime is not operating at this time.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	*30	1	.1	16
Summit Lake (1400′)	29	1	.1	10
Alyeska Mid (1700′)	30	3	.48	19

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	NE	19	57
Seattle Ridge (2400′)	25	**n/a	**n/a	**n/a

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
05/28/22	Turnagain	Avalanche: Turnagain Pass – late May wet slab cycle	CNFAIC Staff
05/21/22	Turnagain	Avalanche: Magnum, Lipps and Tincan	CNFAIC Staff
05/17/22	Turnagain	Avalanche: Sunburst	CNFAIC Staff
05/17/22	Turnagain	Observation: Tincan Ridge	Joe Kurtak
05/11/22	Turnagain	Avalanche: Cornbiscuit and Magnum west faces	CNFAIC Staff Forecaster
05/07/22	Turnagain	Observation: Granddaddy	Kit Barton
04/29/22	Turnagain	Observation: Sunburst wx station	AS/ MM/ AM/ NH
04/28/22	Turnagain	Observation: More Turnagain Pass/Summit Lake wet slab activity	Alex Marienthal
04/27/22	Turnagain	Observation: Magnum	Sykes / Buttrick Forecaster
04/27/22	Turnagain	Observation: Girdwood/Summit/Turnagain Road obs	A S

Riding Areas

Updated Wed, June 01st, 2022

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 as of May 1 per Forest Plan.
Placer River	Closed	Closed as of April 25th due to insufficient snow coverage.
Skookum Drainage	Closed	Closed as of April 1st per Forest Plan.
Turnagain Pass	Closed	Closed as of June 1st.
Twentymile	Closed	Closed as of April 6th due to insufficient snow coverage.
Seward District
Carter Lake	Closed	Closed as of May 1 per Forest Plan.
Lost Lake Trail	Closed	Closed as of May 1 per Forest Plan.
Primrose Trail	Closed	Closed as of May 1 per Forest Plan.
Resurrection Pass Trail	Closed	Closed as of May 1 per Forest Plan.
Snug Harbor	Closed	Closed as of May 1 per Forest Plan.
South Fork Snow River Corridor	Closed	Closed as of May 1 per Forest Plan.
Summit Lake	Closed	Closed as of May 1 per Forest Plan.