Sun, January 18, 2015 Turnagain Pass Avalanche Forecast

Sun, January 18th, 2015

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

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. 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

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

Lingering wind slabs formed during last Wednesday and Thursday’s storm, along with continued strong Easterly winds on Friday, will be the primary avalanche problem in the backcountry. These slabs are roughly 1-2′ thick and composed of hard/dense snow. They are confined to elevations above 3,000′ just off ridgelines and in other catchment zones such as cross-loaded gullies. With a dusting of 1-3″ of low density snow in the past day and a half, they are likely to be somewhat obscured. They are also likely to be quite stubborn and hard to trigger and will most likely take slope angles approaching 40 degrees or steeper to get them to pop out.

If you find yourself venturing into high elevation more extreme terrain, remember your safe travel techniques – mainly exposing one person at a time on a slope. These slabs are hard so pole tests may not tell you much. Also, other red flags such as shooting cracks and hollow feeling snow may not be present until it’s too late.

Photo below: Winter has returned, for the time being, above 2,500′ – a welcome sight!!

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

Although glide activity appears to be slowing down in the region, cracks are likely still opening and the possibility remains for these to avalanche. The most recent glide avalanche is suspected to be in the past 48 hours. This was in upper Lyon Creek on a West aspect (photo below, taken looking East from Tincan). Most of the activity we have seen has been in the 2,500-3,000’ elevation band and on all aspects. Glide avalanches are unpredictable and are best managed through avoidance, as they can release at anytime. If you are traveling along valley bottoms watch for cracks above and limit your exposure when passing below them.

Most recent suspected glide avalanche in the Turnagain Pass region below:

Weather

Sun, January 18th, 2015

A welcome 2″ or so of new snow fell yesterday during the early morning hours above 1,500′, which was followed by gradually clearing skies and light Easterly winds. Overnight, we have seen an additional trace of new snow down to 1,000′ on Turnagain Pass. Ridgetop winds have remained light from the East while temperatures have stayed cool, mid 20’sF on the ridgelines and 32F at 1,000′.

Today, we can expect intermittent cloud cover and snow showers throughout the Eastern Turnagain Arm zone with the rain/snow line hovering just above sea level. Snow accumulations are expected to be small, around 1″. Ridgetop winds should be light and variable and temperatures look to stay in the mid 20’s F on Ridgetops and around 34F at 1,000′.

For Monday, we should see the cooler air, light variable winds and partly cloudy skies continue with little to no precipitation. Our next shot at precipitation looks to be Wednesday. Stay tuned.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	30	1	0.1	30
Summit Lake (1400′)	29	3	0.2	8
Alyeska Mid (1700′)	32	1.5	0.14	18.5

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	E	7	19
Seattle Ridge (2400′)	27	N/A: Wind	sensor	is rimed

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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