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Thu, January 9th, 2014 - 7:00AM
Fri, January 10th, 2014 - 7:00AM
Kevin Wright
Avalanche risk The Bottom Line

Persistent slab concerns keep us at  CONSIDERABLE  above treeline.  The overall stability trend is very slowly improving, but large human triggered avalanches are still likely in specific areas.  Another avalanche near Summit Lake yesterday emphasizes that point.

Slopes above treeline, greater than 35 degrees, and in shallower areas or complex terrain should be avoided.  If an avalanche is triggered today, it is likely to be large, 2-3 feet deep, may be triggered remotely, and cause connected slopes to avalanche sympathetically.  

Thu, January 9th, 2014
Above 2,500'
3 - Considerable
Avalanche risk
2 - Moderate
Avalanche risk
Below Treeline
Below 1,000'
2 - Moderate
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. 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
  • Persistent Slabs
    Persistent Slabs
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
More info at Avalanche.org

The persistent slab problem continues to trend toward less likely, but large high consequence avalanches will result if triggered.  Snow pits are showing mixed results now…  Sometimes the layers are not reacting.  It’s worth keeping in mind that all pit information is overruled by other signs and symptoms.  Collapsing, or recent avalanche activity means that the snowpack is inherently unstable, and steeper slopes can slide.  

The photo below is from yesterday on Tenderfoot at Summit lake. Click here for a writeup and another photo. The Summit region is often a poor comparison to Turnagain Pass or Girdwood, but right now it represents what any shallower snowpack areas can do.  This is another remotely triggered avalanche, one of many in the past week.

Recent snowfall (over 2 feet of wet snow in the last 10 days) has now consolidated into a fairly strong and connected slab.  This is good because it is now more difficult for a person’s weight to penetrate that dense layer and collapse the weaker snow at or below the drizzle crust.  However, it’s bad because the resulting avalanche when a trigger point is found is now larger and more dangerous.  The likelihood of triggering has decreased, but the avalanche size and destructive force has increased.

Trigger points are likely to be shallower wind stripped pockets, possibly close to exposed rocks or trees.  

Thu, January 9th, 2014

A few inches of snow have accumulated since Tuesday.  In general, the weather has not contributed a lot to the avalanche danger since the larger storm on Saturday/Sunday.

Today, mostly cloudy skies are expected.  Isolated snow showers are in the forecast today and tomorrow, with little accumulation.  Wind should be light.  Temperatures continue in the 20s, with a slight decreasing trend on Friday.  

Watch for aurora displays tonight if the skies are clear enough.  A large solar storm may bring active displays to lower latitudes.  

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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.