Sat, April 05, 2014 Turnagain Pass Avalanche Forecast

Sat, April 5th, 2014

Alpine

Above 2,500'

1 - Low

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

It looks like another day of normal caution, with a couple extra thoughts regarding accumulating snow. Any avalanche activity today will be shallow, no deeper than the surface snow that we’ve been on for the last 3 weeks.

If snowfall today is 4 inches or less as predicted, the worst avalanche problems should be very small and manageable – not really a danger, but something to watch. If more than 6 inches falls today, wind slabs could reach 1 foot deep and will be poorly bonded to the surface underneath – these could be a game changer in steep terrain and not something you want to mess with.

As we all hope for another good winter storm, we can’t forget about the old surface conditions that make up the new interface of concern in the snowpack. South faces have been baking in the sun for the last 3 weeks, and freezing up hard at night. North faces have been faceting out into unconsolidated sugar snow. Surface hoar is present nearly everywhere we’ve looked the last few days. All of these components will be difficult for new snow to bond to, making for potentially unstable conditions when the new snow becomes deep enough.

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

The old cornice problem is still present. As always, give the mature overhanging cornices a wide berth when traveling on ridge tops. With new snow and wind, cornices will be growing again for the next few days.

Weather

Sat, April 5th, 2014

Temperatures moderated just a bit yesterday, with slightly higher lows and lower highs. Winds have increased. A tiny bit of snow started falling yesterday, but no more than an inch.

For today the snow amount is predicted to be 1-4 inches, with a snow/rain line at 1300 feet. Look for a southeast wind of 16-32mph.

The outlook through Sunday looks like more of the same. The precipitation intensity is not expected to be very significant. With a few days of snow showers we might see enough accumulation to change surface conditions for the better and produce some small avalanche activity.

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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