Fri, February 12, 2016 Turnagain Pass Avalanche Forecast

Fri, February 12th, 2016

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

2 - Moderate

0 - No Rating

1 - Low

2 - Moderate

3 - Considerable

4 - High

5 - Extreme


Travel Advice	Generally safe avalanche conditions. Watch for unstable snow on isolated terrain features.	Heightened avalanche conditions on specific terrain features. Evaluate snow and terrain carefully; identify features of concern.	Dangerous avalanche conditions. Dangerous avalanche conditions.	Very dangerous avalanche conditions. Travel in avalanche terrain not recommended.	Extraordinarily dangerous avalanche conditions. Avoid all avalanche terrain.
Likelihood of Avalanches	Natural and human-triggered avalanches unlikely.	Natural avalanches unlikely; human-triggered avalanches possible.	Natural avalanches possible; human-triggered avalanches likely.	Natural avalanches likely; human-triggered avalanches very likely.	Natural and human-triggered avalanches certain.
Avalanche Size and Distribution	Small avalanches in isolated areas or extreme terrain.	Small avalanches in specific areas; or large avalanches in isolated areas.	Small avalanches in many areas; or large avalanches in specific areas; or very large avalanches in isolated areas.	Large avalanches in many areas; or very large avalanches in specific areas.	Very large avalanches in many areas.

Avalanche Problem 1

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

Temperatures staying above freezing and rain falling to around 2200′ have elevated the concern for glide avalanches. There are many glide cracks that haven’t released, especially on Seattle Ridge, in terrain that threatens where people recreate. Today is a good day to stay away from these slopes and the runout zones. The large release on Eddies yesterday illustrates the magnitude of this hazard. New cracks may also appear and release without warning. This whole glide phenomenon is very unpredictable and the best advice is to steer clear!

Glide avalanche on Eddies. This released sometime late 2/10-early 2/11.

Avalanche Problem 2

Wet Loose

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

More info at Avalanche.org

An inch of water fell yesterday as rain to approximately 2200′ (closer to 2″ in Girdwood Valley). This began to saturate the settled storm snow and wet loose activity was observed.Temperatures at 1880′ (Center Ridge) were above 32F for 24 hrs. Additional rain today will continue to add stress and decrease strength as it penetrates into the snow stitting on the 1/27 rain crust. Wet loose and wet slab avalanches are likely in the mid-elevation band (1000′-2500′) in steep terrain.These may occur naturally or be triggered by the weight of skier or snowmachiner.

Skier triggered roller balls on Tenderfoot.

Additional Concern

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

There are a variety of storm snow concerns today.

Storm Slabs: This warm, wet snow should bond quickly to the surfaces below but the warmer snow over slightly colder snow may create storm slabs. Quick hand pits are a good way to determine if the new snow is sticking to the old snow.

Wind slabs: Yesterday above approximately 2200′ we received a foot of new snow and sustained winds. It will be possible to trigger a wind slab in steep wind-loaded terrain. Be on the lookout for stiff, pillowed snow and shooting cracks.

Cornices: The fresh snow/wind combination will also add to already large cornices that may be very tender due to warm temperatures. Avoid travel on or below these behemoths.

Persistent Slab: In areas outside of our core forecast zone, including South of Turnagain Pass and the Summit Lake area, the snowpack is shallower and harbors various weak layers; the most notable weak layer is a layer of buried surface hoar 2-3′ deep in the pack. We have found these to be unreactive in the past week but with the warm weather and additional load they could re-activate. For more information see this report from the Lynx Creek drainage and the avalanche triggered January 30th.

Wind transport in the Alpine on Tenderfoot yesterday.

Weather

Fri, February 12th, 2016

Yesterday was mostly cloudy and rain and snow fell throughout the day. The area recieved 1-2″ of water, with snow falling above 2200′. Winds were from the ENE blowing in the 30s(mph) for most of the day and gusting into the 70s. Tempertatures were in the 30Fs.

Today will be mostly cloudy with another few inches of snow possible or rain showers depending on elevation. Rain/snow line is again forecasted to be around 2200′. Winds will be Easterly 15-30 mph. Temperatures will be in the 30Fs.

Tonight will be slightly cooler and rain/snow showers will continue into tomorrow as the overall pattern persists into the weekend.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	0	1	102
Summit Lake (1400′)	35	0	.3	31
Alyeska Mid (1700′)	33	1.5	1	87

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	26	ENE	25	71
Seattle Ridge (2400′)	28	n/a	n/a	n/a

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
11/16/23	Turnagain	Observation: Tincan Common	William Finley
11/14/23	Turnagain	Observation: Sunburst/Magnum	Adrian Beebee
11/14/23	Turnagain	Observation: Seattle Ridge	Schauer/ Creighton/ Ellis Forecaster
11/13/23	Turnagain	Avalanche: Tincan Trees	Eeva Latosuo
11/12/23	Turnagain	Observation: Sunburst	Schauer/ Creighton/ Nave Forecaster
11/12/23	Turnagain	Avalanche: Goldpan – avalanche	Mike Records
11/11/23	Turnagain	Observation: Tincan Common	Andy Moderow
11/11/23	Turnagain	Observation: Taylor Pass – Sunburst	Wadsworth / Stwertka
11/10/23	Turnagain	Observation: Tincan	Andrew Schauer Forecaster
11/10/23	Turnagain	Observation: Tincan Trees	Michael Kerst

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