Thu, November 24, 2016 Turnagain Pass Avalanche Forecast

Thu, November 24th, 2016

Alpine

Above 2,500'

3 - Considerable

Treeline

1,000'-2,500'

2 - Moderate

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

Persistent Slabs

Persistent Slabs

Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.

More info at Avalanche.org

A widespread layer of surface hoar (that formed on November 15th/16th) is buried 10-20″ below the surface and continues to be reactive. Human triggered avalanches were reported again yesterday. That makes a full week of avalanches… persistent slab avalanches. Yesterday an observer noted being able to get out onto the slab and having it break above as them well as triggering a slope that already had multiple tracks on it. They also noted that it was hard to escape the fast moving slide. These are all reasons to have your guard up, not trust the snowpack and choose your terrain wisely. In addition, folks venturing to Magnum also triggered avalanches in terrain that has not seen traffic yet this season. There are still many slopes that could potentially slide in the Turnagain Pass area. Don’t let your quest to find fresh tracks lure you into a consequential avalanche. If you do go out today pay attention to the surface conditions. What will be buried by new snow? There is a new layer of surface hoar forming and the surface snow is also being weakened(faceting) due to the colder temperatures.

Again, things to keep in mind for the sunny day forecast:

The snowpack is still unstable, remote triggering is possible. Be on the lookout for shooting cracks.

The larger and more connected the slope is, the larger the avalanche = higher consequences
Slabs can break above you, making it more difficult to escape
Be aware of OTHER groups and WHO IS BELOW YOU

Here is a little more information on Persistent Slabs and Travel Advice. This comes from the Utah Avalanche Center’s Avalanche Problem Toolbox, authors: Drew Hardesty and Wendy Wagner!

Skier triggered slide yesterday on Sunburst. Slope had previous tracks on it. Photo: Mike Records

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

There were two glide avalanches reported in the past two days and glide cracks are visible in the other pieces of terrain. Give these wide berth, minimize time spent underneath glide cracks and remember these are totally unpredicatable. They are not triggered by humans and are the entire snowpack releasing.

Sunburst glide avalanche and glide crack. This released sometime between Tuesday afternoon and Wednesday morning. Photo: David Evans

Weather

Thu, November 24th, 2016

Yesterday was a clear sunny day in the mountains. Winds were light and temperatures were in the mid 20Fs. Overnight the temperatures dipped into the teens in valleys and winds remained light and variable.

Today will be similar with clear skies and temperatures in the 20Fs. WInds will pick up to 10-20mph from the NW. There will be increasing clouds overnight and a chance of snow showers.

Tomorrow will be mostly cloudy with snow showers, 0-3″ possible. This system is forecasted to linger and bring snow to the region into next week.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	24	0	0	18
Summit Lake (1400′)	14	0	0	2
Alyeska Mid (1700′)	27	0	0	2

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	24	variable	3	12
Seattle Ridge (2400′)	26	variable	3	9

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
04/15/24	Turnagain	Observation: Seward Highway – Tern Lake to Portage	Joel Curtis
04/14/24	Turnagain	Observation: Sunburst	T. Olsen-Lund, R. Sullivan I. Adams
04/14/24	Turnagain	Observation: Turnagain Pass Snomo	K. Gallaher
04/13/24	Turnagain	Observation: Spokane Creek	Everet Megli
04/11/24	Turnagain	Observation: Tincan	John Sykes Forecaster
04/10/24	Turnagain	Avalanche: Seattle Ridge	Schauer/ Keeler Forecaster
04/10/24	Turnagain	Observation: Cornbiscuit South Face	Todd Kelsey
04/10/24	Turnagain	Avalanche: Tincan	N. Dumont J. Carlberg

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