Sun, March 06, 2016 Turnagain Pass Avalanche Forecast

Sun, March 6th, 2016

Alpine

Above 2,500'

2 - Moderate

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

Dry Loose

Dry Loose

Dry Loose avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.

More info at Avalanche.org

Welcome to spring! Even yesterday when skies were mostly covered with clouds the sun’s radiation still played a role in heating the surface of the snow. The sun’s warmth combined with already warm daytime temperatures has the potential to add stress to our avalanche concerns: wind slabs, loose snow, and cornice fall. Monitor the surface snow and plan your day accordingly.

Loose Snow: Yesterday’s new snow (5”) was not bonding well with the surface below and was easily triggered on steep test slopes. This new snow was fast moving and released easily from your ski tips. Keep this problem in mind if entering into terrain where falling could have high consequences. This avalanche problem can be managed by letting your ‘sluff’ move past you when descending. On solar aspect in the afternoon wet loose avalanches will be more difficult to manage and harder to escape. Look for natural point releases on steep slopes, near rocks, and consider avoiding aspects where the sun is heating the slope.

Wind Slabs: Yesterday this new snow arrived with moderate winds and just enough time has passed to help form cohesive slabs. It is unknown how well this new snow is bonding with the surface below, thus be on the lookout for wind slabs in the alpine. Pay attention for soft pillow shaped features, shooting cracks and ease into steeper terrain with caution.

Top 5″ of loose snow was easily triggered yesterday on steep test slopes in 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

Countless glide cracks continue to threaten large areas of terrain throughout Turnagain Pass, including a mine field of cracks that cover most of the Southwest face of Cornbiscuit. There were several glide cracks that slid on Friday in the Summit Lake area and one possible new glide avalanche in the Lynx creek drainage. Glide cracks have been widening and coming out of hiding after they were covered by wind and snow during the storm cycle that ended a week ago. Limiting time spent under cracks is crucial, as they will spontaneously release without warning.

One of several many large glide cracks along Cornbiscuit’s Southwest face. Photo by Kevin Dee.

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

Very large cornice features can be found along most ridgetops throughout Turnagain Pass. Some have large cracks and remain precariously perched in place. As is the general rule, give them lots of space, and limit time under them. Today warming temps and sun will be adding more stress and a snowmachine or person too close could tip the balance.

Some cornice features may have large cracks like this one that overhangs the SW aspecet of Magnum. Photo taken on 3-2-2016

Weather

Sun, March 6th, 2016

Yesterday snow and rain showers left 6 € of new snow in the Turnagain Pass area, 2 € happened before 7am yesterday. By late morning snow turned to rain along the highway and a brief period of sun appearted mid-day. Rain/snow line was around 1400′. Temperatures spiked in the high 30’s F at Center Ridge Weather Station and Easterly ridgetop winds were moderate become light in the afternoon and evening.

Overnight temps remained just above freezing along the road corridor (33F) and skies remained overcast. Winds were light with no new accumulation after midnight.

Today expect isolated rain and snow showers throughout the morning and afternoon becoming partly cloudy by early evening. Temperatures are expected to reach the mid-high 30’s F by mid-day with sun being an influence with thin cloud cover.

Tomorrow a similar pattern of rain and snow showers will continue to move through Southcentral, Alaska.

Today’s weather forecast for scattered showers can produce a ‘greenhouse effect’ where thin cloud cover can trap short wave radiation from the sun and easily heat up the surface of the snow.

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

	Temp Avg (F)	Snow (in)	Water (in)	Snow Depth (in)
Center Ridge (1880′)	32	4	0.4	141
Summit Lake (1400′)	33	1	0.1	44
Alyeska Mid (1700′)	33	7	0.7	108

RIDGETOP 24-hour data (6am – 6am)

	Temp Avg (F)	Wind Dir	Wind Avg (mph)	Wind Gust (mph)
Sunburst (3812′)	25	ENE	15	49
Seattle Ridge (2400′)	27	n/a	n/a	n/a

Observations

Recent Observations for Turnagain Pass

Date	Region	Location	Observer
04/15/24	Turnagain	Observation: Taylor Pass	John Sykes Forecaster
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
04/10/24	Turnagain	Avalanche: Cornbiscuit	Tyler Grundstrom
04/07/24	Turnagain	Observation: Seattle Creek Headwall	Troy Tempel

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