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ARCHIVED - Forecasts expire after 24 hours.
Issued
Fri, January 10th, 2014 - 7:00AM
Expires
Sat, January 11th, 2014 - 7:00AM
Forecaster
John Fitzgerald
Avalanche risk The Bottom Line

The avalanche hazard is CONSIDERABLE above treeline, where dense slabs 2-3′ in depth sit on top of weak snow. It will take large triggers such as snowmachines or groups of people to initiate an avalanche.   Avalanches in the upper elevations have the potential to be large and destructive today.  

Below treeline, (especially between 1,200-2,000′) the hazard is MODERATE.   Steep terrain, rollovers, and areas with shallow snow are key spots to avoid in the lower elevations today.

Below 1,200′ the snowpack is capped by a thick crust and avalanches are unlikely.

Fri, January 10th, 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. 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

It’s been 5 days since the last significant storm and subsequent avalanche cycle.  In the time since this last storm the weak snowpack has been able to adjust to this newest load.  Each day it becomes more difficult to trigger avalanches.  The weak layers near the bottom of the snowpack have also slowly gained strength.  

However, the problem has not gone away.  Weak snow near the ground continues to show the potential to produce large avalanches.  Potential slab depth ranges from 1 foot in the lower elevations to 3 feet near ridge lines.  

The potential also exists for avalanches to propagate across entire slopes.  Because of these factors, it is important to continue to treat all slopes, especially above 35 degrees, with suspicion.  The obvious warning signs (recent avalanches, shooting cracks, collapsing) will potentially not show themselves.  Now is a time when it is important to know what is below the surface.  When entering avalanche terrain it is important to practice good travel habits; expose only one person at a time, stop in islands of safety, and communicate plans within your group.

Weather
Fri, January 10th, 2014

In the past 24 hours the mountains around Eastern Turnagain Arm have received a trace of new snow.   Ridgetop winds have been light out of a variety of directions averaging 3mph with gusts to 11mph.   Temperatures have been on a slight decline with current ridgetop stations reading 15-18 degrees F.

Today expect cloudy skies with occasional flurries.   Winds will be light out of the NW at 5-10mph. Temperatures will warm into the high 20s F at 1,000′.

The long term outlook calls for a continuation of cloudy conditions with only light precipitation and a gradual cooling pattern.   The next chance for more significant precipitation looks to be towards the middle of next week.

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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.