Fri, January 08, 2016 Turnagain Pass Avalanche Forecast

Fri, January 8th, 2016

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

2 - Moderate

Below Treeline

Below 1,000'

1 - Low

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

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

Triggering a wind slab today in steep leeward terrain is possible today. Winds over the past few days have deposited additional snow, continuing to cross load and top load terrain features. Look for pillowed snow, listen for hollow sounds and pay attention to stiff snow under your skis, snowboards or snowmachines. Investigate if the stiff snow is overlaying soft snow. Watch for shooting cracks and remember even a small pocket of wind slab in steep terrain can have high consequences. Wind slabs are notorious for letting you travel out onto them and then breaking above you. Evaluate carefully before committing to steep terrain from above or below.

****In some parts of the advisory area 5-7′ of settled and wind effected storm snow is sitting on a layer of old faceted snow on top of the Thanksgiving Rain Crust. This still needs to be a consideration as you travel into the backcountry today. This Deep Slab concern is a low probability, very high consequence set-up. As always it is important to use safe travel practices: ride slopes one at a time, have an escape route planned, regroup and/or park in safe areas and watch your travel partners. Do not overload slopes with multiple skiers, boarders or snowmachines.

Wind transporting snow on Turnagain Pass.

Avalanche Problem 2

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

Very large cornice features have formed throughout the region as a result of a two-week storm that deposited ~9’ of snow and was accompanied by very high winds. Cornices have the potential to fall naturally or be triggered by the weight of a person or machine and can be very dangerous. Travel under or on them should be avoided. They have the tendency to break farther back from the ridge than expected and can trigger an avalanche on the slope below by adding a lot of weight quickly. As you approach ridgelines and the entrances to backcountry bowls make sure you aren’t accidently traveling on overhanging snow. A snowmachine took a dip into the cornice crack near the top of the Seattle Creek uptrack.

A large crack was found on the Magnum ridge above the cornice.

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

Glide cracks are continuing to appear throughout Turnagain Pass. They may lead to Glide Avalanches which are incredibly difficult to predict and will be deep and destructive if they do release. Travel under glide cracks should be avoided. In addition the cracks can be quite deep and falling into one could be very hazardous. They are sometimes mistaken for old avalanche crowns. The characteristic “brown frown” shape can help you identify the glide cracks in the terrain.

Glide cracks on Seattle Ridge just north of the common uptrack.

Weather

Fri, January 8th, 2016

Yesterday was mostly overcast. There were a few breaks in the clouds alternating with periods of very light rain/snow showers. Temps were in the 30Fs at 1000′ and in the 20Fs at 3000′. Winds were mostly light from the ENE with a few gusts in the 30s.

Today will be mostly cloudy with light rain and snow showers, 0-2″ of snow. Snow line is forecasted to be around 1800′. Easterly winds will increase throughout the day into tonight as the storm moves into the region. Precipitation is forecasted to be heavier tonight into tomorrow morning. Snow line may increase to 2000′.

This showery pattern will persist through the weekend as the plume of warm moist air is pushed into the area by the low in the Gulf.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	31	0	0	81
Summit Lake (1400′)	30	0	0	26
Alyeska Mid (1700′)	32	0	0	58

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	23	ENE	15	38
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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