Sat, February 06, 2016 Turnagain Pass Avalanche Forecast

Sat, February 6th, 2016

Alpine
Above 2,500'

Considerable (3)

Treeline
1,000'-2,500'

Considerable (3)

Below Treeline
Below 1,000'

No Rating (0)

Alpine Above 2,500'		Considerable (3)
Treeline 1,000'-2,500'		Considerable (3)
Below Treeline Below 1,000'		No Rating (0)

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

Today could be one of those days where someone could easily be caught in an avalanche: It will be our first chance for a break in cloud cover after a 4 day storm and it’s Saturday. The big concern centers around 2-3′ of new snow, which fell between Tuesday and Friday, that sits on a layer of weak older snow. This weak old snow was last weekend’s surface, which became loose and faceted along with a layer of surface hoar on top. Not only that, at the mid-elevations, between 2,000 and 3,000′, a crust exists below the weak snow (see photo below). What this all boils down to is that the new snow may not stabilize very quickly after this storm and people could trigger large and dangerous avalanches through the weekend. Things to keep in mind with this type of snowpack:

1) This unstable ‘set-up’ is one we have not seen this year

2) Triggering an avalanche remotely, from the side, top or below a slope is possible

3) The snowpack between 2,000′ and 3,000′ (where the weak snow/crust combination exists under the new snow) could be more unstable that the higher elevations. Crusts can inhibit stability and contribute to the possibility for remote triggers.

4) With little ground truth information at this point, very cautions terrain selection is required.

5) Sticking to slopes less than 30 degrees – with nothing steeper above you – to give the snowpack time to adjust is a great way to have a safe weekend in the backcountry.

The photo below shows the new snow at 2,000′. At this elevation the snow was very warm and dense; the rain snow line was just below this and lighter and deeper snow existed just above this.

Avalanche Problem 2

Glide Avalanches

Glide Avalanches

Glide Avalanches are the release of the entire snow cover as a result of gliding over the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow. They typically occur in very specific paths, where the slope is steep enough and the ground surface is relatively smooth. They are often proceeded by full depth cracks (glide cracks), though the time between the appearance of a crack and an avalanche can vary between seconds and months. Glide avalanches are unlikely to be triggered by a person, are nearly impossible to forecast, and thus pose a hazard that is extremely difficult to manage.

More info at Avalanche.org

The glide avalanche cycle continues…. Another glide crack released into a full-blown avalanche sometime late on Thursday or early Friday morning. These cracks are clearly still active and avalanching. Again, this is not the type of avalanche that can be triggered, but instead release spontaneously on their own. Just one more reason to avoid being under steep slopes today.

Photo: Glide avalanche on the Southeast face of Seattle Ridge, between the motorized lot and the motorized up-track.

Additional Concern

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

With the warm and sticky nature of the new snow, cornices are likely to have grown even larger (they are already behemoths…) and be on the verge of collapse. These are not only hazards in themselves, but are also likely to trigger large avalanches below.

Weather

Sat, February 6th, 2016

Yesterday we saw the tail end of the storm cycle move out with light snowfall adding roughly 1-3″ of new snow. 1″ fell at the Center Ridge SNOTEL at 1,900′ while 3″ fell in Girdwood Valley at the Alyeska Mid station. Winds died down as well with averages ~15mph from a generally East direction. Temperatures were warm (low 30’s at 1,000′) with a rain/snow line fluctuating between 1,000′ and 1,200′.

This morning we are seeing a quick pulse of moisture, increasing cloud cover and increasing Easterly winds move though. This should exit the region by mid-day and skies may break up if we are lucky. We may pick up another 1-3″ of snow with a rain/snow line ~500′ this morning. Winds are expected to be in the 15-25mph range from the East on the ridgetops. Temperatures look to hover in the upper 20’s at 1,000′ and near 20F at 4,000′.

For Sunday, another band of wind and snow looks to move in. We should see some breaks in this stormy pattern this week hover, so stay tuned.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	28	1	0.1	110
Summit Lake (1400′)	27	1	0.1	32
Alyeska Mid (1700′)	30	3	0.33	87

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	21	NE	15	46
Seattle Ridge (2400′)	25	–	–	–

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
03/26/23	Turnagain	Avalanche: Sunburst avalanche investigation	Schauer/ Cullen Forecaster
03/26/23	Turnagain	Observation: Magnum shoulder	Matthew Howard
03/25/23	Turnagain	Avalanche: Seattle Ridge backside – several human triggered large avalanches	CNFAIC Staff
03/25/23	Turnagain	Avalanche: Seattle Ridge, 3rd Bowl, Rider Triggered Avalanches	CNFAIC Staff
03/25/23	Turnagain	Avalanche: Pastoral	Tony Naciuk
03/25/23	Turnagain	Avalanche: Eddie’s	James Howery
03/25/23	Turnagain	Observation: Eddies lower slopes	Anna Frick Bridget Psarianos
03/25/23	Turnagain	Observation: Sunny Side	Peter Wadsworth
03/24/23	Turnagain	Avalanche: Sunburst/Magnum	Megan Guinn & John Sykes Forecaster
03/23/23	Turnagain	Avalanche: Magnum	Amanda Goss

Riding Areas

Updated Fri, February 10th, 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	Open	Opened Dec 13th.
Placer River	Open	Closed Jan 5th due to lack of snow and reopened Feb 11th.
Skookum Drainage	Open	Closed Jan 5th due to lack of snow and reopened Feb 11th.
Turnagain Pass	Open	Opened Dec 13th.
Twentymile	Open	Closed Jan 5th due to lack of snow and reopened Feb 11th.
Seward District
Carter Lake	Open	Opened Dec 13th.
Lost Lake Trail	Open	Opened Dec 13th.
Primrose Trail	Open	Opened Dec 13th.
Resurrection Pass Trail	Closed	Closed to motorized use for the 2022/23 winter season per Forest Plan. Open next season.
Snug Harbor	Open	Opened Dec 13th.
South Fork Snow River Corridor	Open	Opened Dec 13th.
Summit Lake	Open	Opened Dec 13th.