Thu, February 25, 2016 Turnagain Pass Avalanche Forecast

Thu, February 25th, 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

An intense two-day storm concluded this morning leaving 4’ of new snow in the alpine. Strong Easterly winds averaged 30-40mph and rain was observed to 1500’ and possibly as high as 2000′. Overnight temperatures remained above freezing at 1000’ and today there is a possibility of clearing skies and sun. This is not a good combination for our currently stressed out snowpack! DON’T FORGET WE HAVE RECEIVED 8” of WATER (over 8’ of new snow) in the last FIVE DAYS and experienced a big avalanche cycle during the first storm event on Sunday, Feb.21. Very little information is known about our most recent loading event, but we did recieve several reports of ‘wumpfing’ on Tincan and a seperate group could hear avalanche activty in the Johnson Pass area. What we do know is the only thing that will help this snowpack heal is time and cooling temperatures, both of which we do not have.

Today’s weather forecast has us prepared for everything; scattered rain and snow showers, moderate winds, or periods of clearing skies and a posibility of sun. Should the sun grace us with its presence the likelihood of natural activity will increase today. Below is a list of the avalanche problems to be aware of.

Wind Slabs: This morning moderate Easterly winds will continue to add stress to very large wind slabs. These slabs could be as thick as 4-6’ and have the potential to be large, connected and run to the valley floor. If the sun appears today wind slabs will be extra sensitive to a human trigger. Today it is best to avoid all runout zones and stay off of slopes steeper than 30 degrees.

Wet Snow: Today’s weather forecast is calling for scattered rain showers to 2000’, but there is also a possibility of clearing skies and sun. Both weather concerns can produce wet avalanches, but the sun could have a bigger influence on solar aspects, especially in the alpine.

Cornices: Natural cornice fall activity is possible today and will be an additional trigger of large natural avalanches.

Over 8′ of snow has fallen in the alpine in Turnigan Pass and many of the steep gullies along Seattle Ridge are full of debris.

Yesterday afternoon parking was limited due to 12″ of wet saturated snow along the road corridor of Turnagain Pass.

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

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

Thu, February 25th, 2016

A potent storm that lasted 2 days has ended this morning depositing 3-4′ of new snow (3.4 € of snow water equivalent) in the upper elevations. Yesterday rain was observed to 1500′, but may have reached 2000′ overnight. Temperatures remained above freezing overnight (35F) along Turnagain Pass (1000′). Northeast ridgetop winds were strong for the duration of the storm averaging in the 30-40s mph with gusts in the 70’s.

Today a brief break in the weather has us prepared for everything. Snow and rain showers are anticipated with a possibility of 4-6 € of snow in the upper elevations. It is also possible that we could experience periods of clearing skies and sun. Moderate Easterly ridgetop winds are expected to become light by early evening. Temperatures will remain warm today with snow/rain line as high as 2000′.

Another storm is on track for Friday with several more stacked up behind it. A continuation of rain, snow, strong winds and warm temperatures is anticipated through the weekend.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	33	6-8″ wet snow	1.9	139
Summit Lake (1400′)	34	rain	0.6	44
Alyeska Mid (1700′)	33	3″ wet snow	1.93	106

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	ENE	35	78
Seattle Ridge (2400′)	28	~	~	~

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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