Sun, April 03, 2016 Turnagain Pass Avalanche Forecast

Sun, April 3rd, 2016

Alpine

Above 2,500'

1 - Low

Treeline

1,000'-2,500'

3 - Considerable

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

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 avalanches are unlike any other avalanche problem and don’t fit well in the North American Danger Scale. They release without warning and are not associated with human triggers. They are a high-risk low likelihood avalanche problem, and the only way to mange this problem is by avoiding terrain with glide cracks.

SO WHAT DOES THIS ALL MEAN?

We as avalanche forecasters have NO IDEA which glide cracks are going to release on any given day. What we do know is the frequency of glide avalanches is on the rise. Since Friday (4/1) five large glide avalanches occurred on Seattle Ridge, including one mid-day yesterday. Another handful of glide avalanches were also observed yesterday between Girdwood and Turnagain Pass.

The reason this is so alarming is that new glide cracks are appearing daily and many threaten popular terrain. The Seattle Ridge uptrack is one of our biggest concerns because a large crack now puts this popular route in the line of fire. If you were to be in the wrong place at the wrong time you would not survive a glide avalanche. High marking or setting a skin track under a glide crack is not recommended EVER!

Recent high marking was observed yesterday below a large glide crack on Seattle Ridge. Notice how portions of the uptrack are also within the runout of this fast growing glide.

We were impressed by the frequency and size of the glide activity on Seattle Ridge yesterday compared to the day before.

A glide avalanche occured mid day yesterday on Seattle Ridge accross from the Sunburst parking lot.

Avalanche Problem 2

Wet Loose

Wet Loose

Wet Loose avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.

More info at Avalanche.org

As we work our way through this springtime regime and transition from a winter snowpack to a summer one, it’s time to think about how the surface is warming/softening, or not warming/softening. This is not only for sussing out good ski/riding conditions but for wet avalanche hazards as well. Yesterday we saw unsupportable and wet snow below 2,500′ where it was easy to initiate wet sluffs in steep terrain. Has this wet snow frozen overnight? Most likely there has been a shallow re-freeze limiting any wet avalanche hazard. However, temperatures climbing today and the likelihood of sunshine may soften surface crusts again, allowing for wet avalanche activity to increase throughout the day. Mid elevations below 2500’ will be the most suspect, but you should still pay attention to solar aspects in the Alpine.

Wet snow rule of thumb: If the snow is wet and mushy enough for your boot to sink in up to your ankle, or more, wet sluffs are possible and it’s time to find a more supportable slope. Also, wet sluffs can be quite dangerous as the debris is heavy, can generate a lot of momentum and be extremely difficult to escape.

This a great way to test the strength of the snow. If the snow is unsupportable and you are punching through avoid steep terrain.

Additional Concern

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

We have yet to start seeing cornices begin to fall in earnest, yet it is still wise to give these very large snow features a wide berth along ridgelines and limit your time below them. Cornices typically calve off around now as we move into a springtime snowpack.

Weather

Sun, April 3rd, 2016

Yesterday skies were mostly cloudy and scattered showers left a trace of new snow in the Alpine. Daytime temps reached a high of 42F at Center Ridge SNOTEL and overnight temps reached a low of 28F. In the alpine temperature remained cooler, mid to high 20F’s and ridgetop winds were Light to Moderate from the East.

Today will be mostly sunny and temperatures will likely reach the mid 40F’s at 1000′. In the alpine temperatures are expected to reach the mid 30F’s and Ridgetop winds be light, 5-10mph, from the East. Overnight temps are expected to drop into the 20F’s.

Tomorrow looks like more cloud cover with a chance of scattered rain/snow showers and patches of sun. Similar temps and winds are expected tomorrow.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	35	trace	0.1	118
Summit Lake (1400′)	35	0	0	37
Alyeska Mid (1700′)	35	trace	0.01	105

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	NE	8	23
Seattle Ridge (2400′)	27	SE	14	31

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
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
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

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