Sun, April 13, 2014 Turnagain Pass Avalanche Forecast

Sun, April 13th, 2014

Alpine

Above 2,500'

2 - Moderate

Treeline

1,000'-2,500'

1 - Low

Below Treeline

Below 1,000'

1 - Low

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

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

We were able to eek out a few solid days of blue-sky powder skiing (on northerly aspects) before the grey-bird conditions set in yesterday bringing with it moderate winds from the SE. Winds yesterday began to build shallow wind slabs in the upper elevations where about 6” of loose, unconsolidated snow was available for transport on north aspects.

Loose, unconsolidated snow on a north aspect

yesterday will feed building wind slabs today.

SE winds in the 40-55 mph range and 1-5” of new snow forecasted for today will conspire to manufacture tender wind slabs across the advisory area. Expect bonding to be a mixed bag from ‘stuck-on-like-glue’ to ‘hair-trigger’ given the huge variety of surface conditions that this storm is coming in on. Any moving snow today should be fairly shallow, relegated to the upper-most layer of new wind deposited snow and likely less of a concern for snowmachiners. For skiers, quick hand pits and test slopes today should aid in your decision-making process before committing to any big terrain.

Avalanche Problem 2

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

A bit of fresh snow and substantial wind transport will conspire to push looming cornices ever closer to failure. Without ever really knowing when a cornice may fail it still holds true to simply avoid exposure to these ticking snow-bombs. This observation (and photo) sent in last spring serves as a good reminder that spring in the Chugach is cornice season!

Weather

Sun, April 13th, 2014

Moderate winds and clouds yesterday dominated the weather across the forecast area with little to no precipitation during the daylight hours.

Grey skies and warmer air will persist as moderate SE winds ramp up throughout the day. We should see scattered and light precipitation in the form of light rain at sea level and 1-5 € of new snow above 1100′. Temps at 1000′ will be in the range of 31-40 degrees today. Freezing levels drop to around 700′ at night as moisture tapers off.

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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