Sat, November 19, 2016 Turnagain Pass Avalanche Forecast

Sat, November 19th, 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

WHUMPF... There it is! Winter is here and so are the avalanches. Snow falling over the past two days landed on a widespread layer of surface hoar. Surface hoar is a persistent weak layer, meaning it can be sensitive to triggering for a long time after being buried. Multiple parties yesterday triggered 10-15″ soft slabs in the Alpine. These were easily triggered, fast moving and running long distances. One skier was caught and carried, losing a ski and a pole. Lower angle terrain (18-25 degree slopes) was avalanching which is common with buried surface hoar and requires extra caution. The storm snow was fairly soft but as the wind moved it around it became more of a slab throughout the day and more reactive. Slabs could be even more developed today with additional snow, wind loading and time to stiffen. If this happens these may be more stubborn to trigger but may break above you when you are out on the slab. There is enough snow to take a bad ride if you are knocked off your feet, slide into a terrain trap or get pushed into high consequence terrain. As the first weekend with new snow there will be more people out in concentrated areas. Watch out for people around you and recognize that this surface hoar layer could be triggered remotely. Look for cracking and whumpfing and make conservative terrain choices today. In addition, look for drifted snow, listen for hollow sounds and avoid cornices. Use safe travel techniques and wear your rescue gear and don’t let your early season stoke cause you to make dangerous chioces today. There is a long season ahead of us!

1 cm surface hoar buried 10-15″ below the surface.

Skier triggered avalanches in Common Bowl on Tincan

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

Recent glide avalanches and cracks were observed prior to the recent storm. These may have been covered up but look out for and avoid traveling under glide cracks if you see them. Glide occurs when the entire snowpack slowly slides as a unit on the ground. Glide avalanches can be composed of wet, moist, or almost entirely dry snow and pose a hazard that is very difficult to forecast. They are often preceded by glide cracks (full depth cracks in the snowpack), though the time between the appearance of a crack and an avalanche can vary between seconds and months.

Glide avalanche on Sunburst last week. Glide activity was also observed Tuesday on Eddies.

Weather

Sat, November 19th, 2016

Moisture spinning into the forecast area from the Gulf continues to produce snow. Yesterday was overcast with snow showers throughout the day. Winds were from the NE 10-20 mph gusting into the 30s. Temperatures above 1000′ were in the 20Fs.

Today will be mostly cloudy with a 60% chance of snow. 1-5 inches of new snow is possible as moisture is pushed into the mountains. NE winds will be light. Temperatures will be in the upper 20Fs. Snow showers continue overnight with temperatures around 18F.

Tomorrow will be similar with mostly cloudy skies, snow showers, light winds and temperatures in the 20Fs. An active pattern is forecasted to continue into next week. Stay tuned for more details.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	27	2	.2	18
Summit Lake (1400′)	27	2	.2	4
Alyeska Mid (1700′)	29	1.5	.15	3

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	21	ENE	12	32
Seattle Ridge (2400′)	24	ESE	3	10

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
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
04/29/24	Turnagain	Avalanche: Turnagain aerial obs	Tully Hamer
04/27/24	Turnagain	Observation: Johnson Pass	Noah Mery
04/23/24	Turnagain	Observation: Turnagain Sunny Side	Travis SMITH
04/21/24	Turnagain	Observation: Bertha Creek	Anonymous
04/20/24	Turnagain	Avalanche: Spokane Creek	Schauer/ Mailly Forecaster
04/16/24	Turnagain	Observation: Cornbiscuit	Krueger / Matthys Forecaster

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