Tue, April 26, 2016 Turnagain Pass Avalanche Forecast

Tue, April 26th, 2016

Alpine

Above 2,500'

3 - Considerable

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

The wet spring storm that is impacting our area has added almost 2″ of rain to an already wet snowpack. As the snowpack gets warmer and more saturated below 2500′ the already active glide avalanche cycle may ramp up even more. An additional glide avalanche ran over the uptrack on Seattle Ridge and another piece of the crack on the West face of Magnum also released. Watch for new cracks appearing and avoid travel under existing glide cracks.

West face of Magnum with recent wet loose avalanches and a new glide release adjacent to the one from last week.

New glide avalanche on the Seattle Ridge uptrack (farthest right streak).

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

Turnagain Pass received almost 2″ of water yesterday and another .5″ is forecasted to fall today. The rain is falling onto an already wet snowpack. Human triggered wet loose avalanches are likely below 2500′ and natural ones are possible. Skiers reported triggering a small wet loose avalanche on Sunday. Visibility was limited yesterday but new wet loose avalanches were observed on the West face of Magnum. We have yet to see surface slides gouging into deeper layers but this potential may increase. As the rain/snowline dances around 2500′ rain may fall onto snow and trigger wet loose avalanches as well. We will continue to monitor whether or not the rain is impacting the drier snow in the Alpine. If you are traveling through the glop today pay attention to how deeply you are penetrating into the snowpack, watch for roller balls and remember loose avalanches can knock you off your feet, are hard to escape and can push you into terrain traps.

Wet day at Turnagain Pass

Additional Concern

Wind Slabs

Wind Slabs

Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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

Temperatures at 3000′ have remained below freezing which means the rain falling at the road will have been snow in the Alpine. We suspect 6-12″ have fallen in the past 24 hrs. This combined with the sustained 30-40 mph winds may have formed tender wind slabs along ridgelines. Look for drifted snow and watch for cracking underfoot. The wind and snow may also have added stress to very large cornices. Avoid travel on or under these beasts.

Weather

Tue, April 26th, 2016

Yesterday was overcast and rain fell throughout the day (snow above 2500′?). Temperatures were in the high 30Fs at 1000′ and the high 20Fs at 3000′. Easterly winds were steady 30-40mph with gusting into the 80s.

Today will be mostly cloudy with another .5″ of rain forecasted to fall. Winds will be easterly 15-35 mph potentially increasing in the afternoon. Temperatures will be in the low 30Fs to low 40Fs depending on elevation.

Tomorrow looks to be similar and to quote the National Weather Service, “NO BIG CHANGES IN THE WEATHER FOR THE EXTENDED PERIOD. WEDNESDAY EVENING AND THURSDAY FEATURE AN EXTENSION OF THE CURRENT WEATHER PATTERN.”

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	37	0	1.8	104
Summit Lake (1400′)	41	0	0	15
Alyeska Mid (1700′)	36	0	.8	87

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	28	ENE	33	89
Seattle Ridge (2400′)	30	ESE	25	60

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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