Sun, April 24, 2016 Turnagain Pass Avalanche Forecast

Sun, April 24th, 2016

Alpine

Above 2,500'

2 - Moderate

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 glide avalanche cycle continues with new activity occurring on a daily basis. Fresh piles of dirty debris were observed yesterday on the Seattle Ridge uptrack and on Pete’s South. Earlier this week glides released on the West face of Magnum and Cornbiscuit, and new cracks have formed on Sunburst. Below 3000’ it is very important to identify terrain with existing cracks and avoid travel in the runout of glides.

*The fact that we have been experience multiple nights without freezing temperatures in the 1000’-2500’ is also concerning. With heavy rain in the forecast for tomorrow, the frequency of glide activity may increase in the coming days.

Even though motorized use has closed in Turnagain Pass, traveling on foot is not recomended on Seattle Ridge due to the threat of numerous glide cracks that continue to release.

A large crack observed on Thursday released yesterday above an old glide avalanche on Pete’s South.

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

Last night was the second evening in a row temperatures remained above freezing at Seattle Ridge Weather Station (2400’.) With another warm day forecasted today the possibility of triggering wet loose activity is moving further into the Alpine. Light rain and periods of sun should be anticipated, both adding more water to the snow.

As you move into the upper elevations, stability will improve with the presence of a supportable surface. Remember to avoid steep terrain if the snow becomes unsupportable and your skis or board are sinking into punchy wet snow. This is an obvious sign the snow is loosing its strength. If for some reason the sun makes a stronger appearance than forecasted, natural wet avalanches will be possible in the Alpine.

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

In the Alpine cornices remain large and very warm daytime temperatures will be adding additional stress. Give them extra space and remember they have a tendency to break much further back than expected.

Higher in the Alpine, above 3500’ where the snow is drier, shallow wind slabs are a possibility on leeward and cross loaded slopes. Ease into to steeper terrain with a cautious mindset.

Weather

Sun, April 24th, 2016

Yesterday light rain and overcast skies were observed throughout Turnagain Pass, with a total of 0.2 € of rain at Center Ridge Weather station (1880′.) Daytime temperatures averaged in the mid 40Fs overnight temperatures hovered just above freezing at Seattle Ridge Weather Station. Easterly Ridgetop winds were, 10-25mph.

Scattered rain showers are expected throughout the day with mostly cloudy skis, but periods of sun are always possible. Rain/snow line will be around 2100′ with an addition 0.1 € of (snow water equivalent) expected today. Ridgetop winds, averaging 5-15mph, but will be building by this evening. Daytime high temperatures for 1000′ are expected to be around 48F and overnight lows in the mid 30F’s.

Monday through Tuesday a warm front is expected to move through Southcentral Alaska. Periods of heavy rain and strong winds are expected. Rain/snow line could be as high as 3000′.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	42	rain	0.2	105
Summit Lake (1400′)	42	0	0	18
Alyeska Mid (1700′)	38	rain	0.09	89

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	32	NE	14	45
Seattle Ridge (2400′)	35	SE	14	40

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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