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ARCHIVED - Forecasts expire after 24 hours.
Issued
Sat, January 11th, 2014 - 7:00AM
Expires
Sun, January 12th, 2014 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Specific areas above treeline remain  CONSIDERABLE because we believe very large human triggered avalanches can still be initiated.  Test pit results have not improved since the storm last weekend.  Finding avalanches today will be unlikely unless traveling in steep terrain.  Trigger points, where the weak layer can be collapsed at a shallow point in the slab, may be hard to find.  However, if this were to happen today the resulting avalanche may take the entire slope at 2-3 feet deep.

Below treeline is a MODERATE danger, where  we are still experiencing collapsing (whumphing).  Steep pockets, even at lower elevations should be approached with some caution.  

Sat, January 11th, 2014
Alpine
Above 2,500'
3 - Considerable
Avalanche risk
Treeline
1,000'-2,500'
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. 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
  • 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 is a problem that doesn’t go away quickly.  The last major storm was on Sunday, almost a week ago.  Since that storm, when many large avalanches were recorded, we haven’t seen a lot of avalanche activity.  This is mostly due to a lack of triggers (people) in the backcountry this week.  However, the problem has been bad enough to warrant an extended stretch of elevated danger ratings.  Our test pits performed every day this week have not shown appreciable improvents in the strength or propagation potential of the snowpack.  Check this video for a test done yesterday on Pete’s North.

It’s worth recapping some of our recent avalanche activity to pick out the trends.  Avalanches have been triggering remotely, often from ridges and propagating across large distances.  Wind blown ridges offer a trigger point where the snowpack is shallow and a person’s weight is more likely to collapse the buried weak layer.  In deeper areas, a collapse may still be caused by a larger trigger such as a snowmachine or a group of people.  Avalanches have been observed on all aspects (N, S, E, and W), and elevations from just below treeline to >3500 feet.  Few people have ventured into higher elevation steep terrain, which is a good self-preservation tactic right now.

Standard warning signs such as whumphing, shooting cracks, or avalanches on small indicator slopes are unlikely right now.  Avoiding steep terrain is the only effective management tool we have to deal with the current problem.

Weather
Sat, January 11th, 2014

No new snow has accumulated in the last 24 hours.  The last major storm ended on Sunday.  This week has been mild weather with warm temperatures, little precipitation, and light wind.

Today we can expect mostly cloudy skies, highs in the mid 20s.  Mostly light wind.

The next storm system may arrive by the middle of the coming week.  Stay tuned.

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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.