Wed, February 24, 2016 Turnagain Pass Avalanche Forecast

Wed, February 24th, 2016

Alpine

Above 2,500'

4 - High

Treeline

1,000'-2,500'

4 - High

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. 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

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

The snowpack was just starting to adjust to the ‘mini-snowpocalypse’ over the weekend and now we are back into an active loading scenario. Overnight we received over a foot of snow and sustained strong winds in the Alpine. Sunburst recorded a peak gust of 105 at 2 am. There is a lot of snow available for transport and snow is forecasted to fall thoughout the day. The NWS service used the phrase heavy at times to describe snowfall rates. Deep wind and storm slabs and large cornices may release naturally as the storm continues today. These will no doubt be very sensitive to human triggers. Visibility will be limited; strong winds will continue and rain is forecasted to fall on the fresh snow in the mid-elevation band up to approximately 1800′.

Today we are again saying travel in or under avalanche terrain is not recommended. Please be patient.

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 the temperature rises and with it the rain/snow line, rain will be falling on new snow. There is the potential for wet loose avalanches in steep terrain in the mid-elevation band. We may see wet slab activity as well due to the stiff crust under this last shot of snow. Wet avalanches are yet another reason to avoid travel in or under avalanche terrain today.

Additional Concern

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

Underneath all the new snow glides are still lurking and have the potential to release at any time. Glides threaten a lot of well-travelled terrain on both the motorized and non-motorized side of the highway. Still looking for a reason to avoid avalanche terrain and runout zones today??? Here is one more avalanche dragon to steer clear of.

Weather

Wed, February 24th, 2016

Yesterday was cloudy and visibility was limited. Snow fell throughout the day with over a foot of accumulation overnight. Winds ramped up in the evening blowing in 50-60 mph with a peak gust of 105. Temperatures were in the 20Fs. Rain/snowline was around 300′.

Today will be mostly cloudy and snow and rain are forecasted to be heavy at times with another inch of moisture expected today and another 1.5 inches tonight. These means a total of 15-30 inches of snow at higher elevations is possible. Winds will be Easterly, 25-50 mph and temperatures will be in the mid to high 30Fs. Rain/snow line is expected to rise to 1800′.

There may be a minor lull in this active weather during the day Thursday with some lingering showers. Another system is forecasted to move in Thursday evening or Friday morning.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	30	14	1.5	134
Summit Lake (1400′)	32	4	.4	45
Alyeska Mid (1700′)	31	9	1	105

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	22	ENE	45	105
Seattle Ridge (2400′)	25	n/a	n/a	n/a

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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