Sun, November 24, 2013 Turnagain Pass Avalanche Forecast

Sun, November 24th, 2013

Alpine
Above 2,500'

Moderate (2)

Treeline
1,000'-2,500'

Low (1)

Below Treeline
Below 1,000'

Low (1)

Alpine Above 2,500'		Moderate (2)
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

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 heard of one human triggered avalanche yesterday. This was in Turnagain Pass on a SSW facing slope of Sunburst. It was triggered by a skier that was ski cutting the slope. The avalanche ran to the valley floor – around 1,000ft. A photo of the crown is below. A few more details HERE.

Photo: Corky Still

It has been just over two days now since we received a foot of heavy snow on top of a 10″ thick layer of faceted snow. There was widespread avalanching during and right after the storm on Friday along with one skier triggered avalanche on Tincan. The culprit weak layer was the Nov 10 faceted snow. Facets are a common persistent weak layer and hence the use of the ‘persistent slab’ icon above. From the report on Sunburst, it sounds like this was a classic case of a wind slab over facets.

Image below is the Tincan skier triggered slide from Friday, Nov 22nd. (more details with the above link)

Though the snowpack is stabilizing, it is doing so slowly. The addition of 1-3″ of new snow should not tip the balance but any recent wind loading could. For anyone getting out today onto the steeper slopes, I’d suggest having your escape route planned in case the slab releases. Steering clear of any recent wind deposited snow will be a good bet as well. The poor structure is there in most locations above treeline – as you can see by the snow profile below – and though the slab is slowly deteriorating, making it harder to trigger, it is still there for now.

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

Winds are slated to kick back up today from the east/southeast – blowing moderate (15-30mph). This, combined with a possible 3″ of new snow as well as existing snow to transport, should be enough factors to form fresh wind slabs. These likely will be shallow and sitting on a variety of surfaces. As always, be suspect of areas with wind deposited snow. These often have the tell-tale signs of a smooth rounded surface and hollow feeling.

Weather

Sun, November 24th, 2013

A somewhat weak weather system will be moving over us today from the southeast. Cloud cover has set in and between a trace to an inch of snow has fallen as of 6am this morning. Temperatures have increased overnight with mountain tops approaching 20F and sea level areas are in the low 30’s. Winds have increased from the east/southeast and are blowing ~15mph with gusts to 30mph.

Today we are expecting 1-3″ of light snow (up to .3″ water) above treeline. Temperatures should remain in the mid 20’s at treeline and winds continue to blow in the 15mph range with gusts to 30 from the east. Basically, a mild snow/weather day with limited visibility. A chance for freezing rain exists at sea level.

Monday, we should see skies clear up as we have a break between systems. Winds should continue from the east but settle down and temperatures remain mild in the 20’s.

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.