Tue, April 12, 2016 Turnagain Pass Avalanche Forecast

Tue, April 12th, 2016

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

3 - Considerable

Below Treeline

Below 1,000'

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. Careful snowpack evaluation, cautious route-finding, and conservative decision-making essential.	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

Glide avalanches remain our primary concern as they continue to release in areas we recreate. The most concerning zone is Seattle Ridge and the popular motorized up-track. This well traveled slope is hanging in the balance (pictured below). Although much of the snowpack has already avalanched along Seattle Ridge, there is still more to come… Due to the dangerous and destructive power of even a small glide avalanche, we are recommending that people do not travel in avalanche terrain (including runout zones) on the motorized side of Turnagain Pass (West Side). Glide avalanche hazard also exists on the non-motorized slide of Turnagain Pass. Travel underneath existing glide cracks is not recommended. In addition, be on the lookout for new glide cracks forming.

New glide avalanche activity (from the past 24-hours) includes Max’s South face, and two on Easterly facing slopes in the Summit Lake area.

Photo: Max’s Southerly face – this glide released mid-slope and you can see a crack to the looker’s left that is prime to release:

Photo: Summit Lake fresh glide avalanche. There is little snow on these slopes but they still clearly pose a threat!

Seattle Ridge Glide Activity:
Although visibility was poor yesterday it looks as though no new glide avalanches occurred. We should be able to see these as they create such brown streaks and dirty debris piles. However, there may have been new wet snow avalanches considering it was difficult to see white(ish) debris.

Photo: Repeat Offender slide path with older glide avalanches running over the lower part of the up-track and cracks threatening rest of the up-track:

Seattle Ridge glide older glide activity seen across from the motorized lot:

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

As temperatures rise today watch for any superficial re-freeze of the snow surface to soften; if the sun pokes through this will speed up the process dramatically. How much re-freeze occurred last night is tough to tell as the cloud cover was in and out (clear skies overnight can re-freeze the surface even in temperatures are as warm as 40F….due to longwave radiation loss). If you find yourself on a steep slope with saturated wet snow then triggering a wet loose avalanche, or push-a-lanche, in steep terrain will be possible.

Additional Concern

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

At the uppermost elevations, where dry snow exists, watch for lingering wind slabs on steep leeward slopes. These areas are in the 3,500′ range and higher. Also, cornices could start falling any day now with these warm temperatures and limiting time under them as well as giving them a wide berth is recommended.

Weather

Tue, April 12th, 2016

Partly cloudy to obscured skies filled the region yesterday. Light precipitation fell along Turnagain Pass adding up to 2″ of new snow above 2,500′ and .2″ of rain below. Ridgetop winds were averaging in the 10-15mph range with gusts to 40mph from the East at the Sunburst weather station.

Today, we should see clouds move in with a chance for breaks in cloud cover here and there through the day. No precipitation is expected and temperatures are slated to be warm…..up to 45F at 1,000′ and 35F on the ridgetops. Ridgetop winds are expected to be ~10mph from a generally Easterly direction.

Looking forward to Wednesday and later this week, we remain in an unsettled weather pattern as a series of low-pressure systems spin to our South in the Gulf shooting moisture our way.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	34	1	0.2	115
Summit Lake (1400′)	36	0	0	32
Alyeska Mid (1700′)	36	0	0	101

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	NE	15	46
Seattle Ridge (2400′)	30	SE	12	30

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
10/27/24	Turnagain	Observation: Tincan	Michael Kerst
10/21/24	Turnagain	Observation: Turnagain Pass Road Observation	Trevor Clayton
10/19/24	Turnagain	Observation: Tincan – Below Todds Run	Andy Moderow
10/18/24	Turnagain	Observation: Taylor Pass	Eli Neuffer
10/15/24	Turnagain	Observation: Tincan Common	John Sykes Forecaster
10/14/24	Turnagain	Avalanche: Tincan	CNFAC Staff
05/13/24	Turnagain	Observation: Eddie’s, Sunburst, Seattle, Cornbiscuit, Pete’s South	H Thamm
05/13/24	Turnagain	Observation: Turnagain Pass non-motorized side	Amy Holman
05/12/24	Turnagain	Observation: Warm up Bowl	Tony Naciuk
05/07/24	Turnagain	Observation: Turnagain Pass Wet Slabs	A S

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