Sat, April 02, 2016 Turnagain Pass Avalanche Forecast

Sat, April 2nd, 2016

Alpine

Above 2,500'

1 - Low

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

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

The primary concern for today will center around glide avalanches, for the countless time this season… These avalanches show no signs of abating and each day we see at least one new glide crack that has released. They are occurring on all aspects and predominantly at elevations ~3,000′ and below. To make matters a bit more concerning, there have been a couple instances where a glide avalanche occurred where no crack was present the day before. This is a tough situation to manage considering the snowpack as a whole is mostly stable.

Continuing to avoid being under cracks is our best bet, and will be till the snow melts out and/or sluffs off the mountains for the summer.

Snowmachiners: The Seattle Ridge up-track is threatened by a large glide crack and a few smaller ones that have yet to release.

Glide cracks and glide avalanches litter Seattle Ridge:

More of the same on Tincan Ridge:

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 possibility of sunshine may soften surface crusts again, allowing for wet avalanche activity to be possible.

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.

Wet and ‘punchy’ snow exists at the lower elevations:

*With the recent winds could we have wind slabs? Possibly in the high elevations. These would likely be shallow and scattered along peaks above 3,500′. There is very little snow available for transport currently.

Winds blow a trace of snow around at the higher elevations where the snowpack is capped by a thin surface crust:

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

Sat, April 2nd, 2016

Weather conditions yesterday consisted of partly sunny skies, a cool Easterly breeze and warm temperatures out of the wind. Ridgetop winds during the past 24-hours have been blowing steady in the 15-30mph range with gusts over 50mph from a generally East direction. Ridgetop temperatures have been cooling slightly, from ~30F to the mid 20’sF.

For today we are expecting partly cloudy skies with a chance for a trace of snow above 1,500′ and chance for rain below. It will be one of those inbetween storm days with sunny spots here and cloudy spots there. Ridgetop winds are expected to lessen to the 10-15mph range from the East and temperatures should climb a bit, to the upper 20’s to 30F at the ridgetops.

Sunday is likely to be much the same as today. We will still be inbetween major storm systems with a chance for partly sunny to mostly sunny skies.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	37	rain	0.1	120
Summit Lake (1400′)	38	0	0	37
Alyeska Mid (1700′)	36	rain	0.1	106

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	27	NE	21	52
Seattle Ridge (2400′)	30	SE	23	47

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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