Fri, December 30, 2016 Turnagain Pass Avalanche Forecast

Fri, December 30th, 2016

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Moderate (2)

Below Treeline
Below 1,000'

Low (1)

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

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

A quick moving storm is impacting Southcentral currently. We have seen light snowfall overnight with an additional 1-3″ expected today. The big news is however, the WIND… Westerly winds are slated to ramp up into the 30-45mph range with stronger gusts along the ridgelines.

Snowfall Totals so far:
Girdwood Valley: 3-5″
Turnagain Pass: 2-3″
Summit Lake: 3-4″

WIND SLAB AVALANCHES:
With plenty of older loose snow available for transport and a few new inches, fresh wind slab avalanches should be expected. These could release naturally, or be easily triggered by a person. They could be anywhere from a shallow 6″ slab to a thicker, more concerning, 18″ slab. This flow direction is known to load Easterly slopes on Seattle Ridge, such as Repeat Offender. On the East side of Turnagain Pass, this flow often loads Northerly slopes on ridgelines such as Tincan, Sunburst and Magnum.

*Keep in mind that newly wind loaded slopes could overload buried weak layers and a wind slab avalanche could ‘step-down’, triggering a larger slab avalanche.

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 are glad to report a positive outcome to a near miss avalanche yesterday on the Lipps ridge. Three skiers were caught and carried in a slab avalanche while they were ascending the common up-track on the lower portion of Lipps. The avalanche was triggered in a thin area and propagated above them. The slab washed over all three and they were carried 1-200′ (estimate) before they all ended up on the surface of the debris. Forecasters will investigate this avalanche today and a more detailed report, with the events shared by the party members along with avalanche details, will be finalized soon. You can see more photos in the preliminary report HERE.

PERSISTENT SLAB AVALANCHES:
The Lipps slide was believed to be a persistent slab that broke in weak faceted snow 1-2′ below the surface. This set up exists South of Turnagain Pass (including Johnson Pass and Lynx drainages). There is a variety of weak layers that sit 1-3′ below the surface and triggering a slab breaking in the old snow remains possible. Pay attention to:

Whumpfing / collapsing
Cracking in the snow
Hard stiff snow over softer old sugar snow
Thin areas of the slab – these are likely trigger points
These avalanches can occur when no signs are present as well – more reasons to follow safe travel protocols.

Photo from the Lipps avalanche yesterday taken by a member of the group involved. We thank these folks for their willingness to share.

Weather

Fri, December 30th, 2016

Mostly overcast skies covered the region yesterday. Ridgetop winds were light from the North and East and no precipitation fell. Temperatures rose dramatically from single digits at 7am to 20F by 7pm (in response to a warm air mass moving through from the West).

Overnight, we have seen light snowfall in Girdwood, Turnagain Pass and Summit Lake as a warm storm system impacts Southcentral. This system looks to be favoring the Girdwood and Western Kenai Mountains, including Summit Lake, snowfall totals mentioned above and in chart below. Another 1-3″ of snowfall is forecast for today before skies begin to break up. STRONG Westerly ridgetop winds (30-45mph) are expected during today bringing cold air – it should be chilly and blizzard like on the ridgelines!

Tomorrow, the cold single digit air mass will remain over us with clear skies and no precipitation expected.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	19	2	0.2	39
Summit Lake (1400′)	17	3	0.3	12
Alyeska Mid (1700′)	20	3	0.3	29

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	Under Repair	Under Repair	Under Repair	Under Repair
Seattle Ridge (2400′)	17	SE	15	33

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
12/08/19	Turnagain	Avalanche: Tincan	Ryan Van Luit Forecaster
12/06/19	Turnagain	Avalanche: Sunburst	Billy Finley
12/04/19	Turnagain	Observation: Sunburst	A.Johnston-Bloom/ W.Wagner/ R.Van Luit Forecaster
12/03/19	Turnagain	Observation: Hippy Bowl	Nick Langowski
12/01/19	Turnagain	Observation: Tincan, All elevations	Eric Roberts
12/01/19	Turnagain	Observation: Tincan	Andy Moderow
11/30/19	Turnagain	Observation: Tincan Treeline Plateau/ Common Bowl/ Ridge	Eric Roberts
11/29/19	Turnagain	Observation: Sunburst Ob #2	Aleph Johnston-Bloom Forecaster
11/29/19	Turnagain	Observation: Sunburst Ob #1	Aleph Johnston-Bloom Forecaster
11/27/19	Turnagain	Observation: Tincan	Aleph Johnston-Bloom Forecaster

Riding Areas

Updated Mon, December 02nd, 2019

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.
Placer River	Closed	Closed.
Skookum Drainage	Closed	Closed.
Turnagain Pass	Closed	Closed.
Twentymile	Closed	Closed.
Seward District
Carter Lake	Closed	Closed.
Lost Lake Trail	Closed	Closed.
Primrose Trail	Closed	Closed.
Resurrection Pass Trail	Closed	Closed. Will be open for the 2019/20 season pending adequate snow cover.
Snug Harbor	Closed	Closed.
South Fork Snow River Corridor	Closed	Closed.
Summit Lake	Closed	Closed.