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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, April 5th, 2014 - 7:00AM
Expires
Sun, April 6th, 2014 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Change is finally happening.  A small amount of snow is expected to fall above 1300 feet today.  At current snowfall predictions I do not expect the avalanche danger rating to rise.  However, if snow comes in deeper than predicted, watch for touchy wind slabs on top of the old tired surface.  

The overall danger rating is  LOW this morning, but new snow will probably make that rise to pockets of  MODERATE  above treeline  by tomorrow.  

Sat, April 5th, 2014
Alpine
Above 2,500'
1 - Low
Avalanche risk
Treeline
1,000'-2,500'
1 - Low
Avalanche risk
Below Treeline
Below 1,000'
1 - Low
Avalanche risk
0 - No Rating
1 - Low
2 - Moderate
3 - Considerable
4 - High
5 - Extreme
Avalanche risk Avalanche risk Avalanche risk Avalanche risk Avalanche risk
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. Dangerous avalanche conditions. 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 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
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.  

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This is a general backcountry avalanche advisory issued for Turnagain Arm with Turnagain Pass as the core advisory area. This advisory does not apply to highways, railroads or operating ski areas.