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ARCHIVED - Forecasts expire after 24 hours.
Issued
Thu, November 28th, 2013 - 7:00AM
Expires
Fri, November 29th, 2013 - 7:00AM
Forecaster
Kevin Wright
Avalanche risk The Bottom Line

Happy Thanksgiving!

A few inches of fresh dry snow yesterday will not be changing the overall avalanche danger.  Above treeline remains  MODERATE, for smaller reactive slabs in wind loaded areas.  The backcountry is slowly moving towards stable, in fact the more important safety issue is probably related to exposed rocks and trees with thin snow cover.  

Below treeline is LOW danger with very shallow snow coverage.

Special Announcements

All of Chugach National Forest remains closed to off-road motorized use due to a lack of sufficient snow cover.  Snowmachines will be permitted when the snow is deep enough to protect the ground underneath.

Thu, November 28th, 2013
Alpine
Above 2,500'
2 - Moderate
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. 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

When you take your skis off and try to walk around in your boots, the lack of strength in the snowpack is instantly apparent.  My boots sank through all the layers, only stopping at the ground a little more than 2 feet down.  The slab/weak layer combination is still the same as it was last Friday, but not nearly as unstable as it was then.  The same equation is there, with stronger and denser storm snow from Nov. 21st on top of very weak and loose faceted snow.  The reason why we don’t have a big problem at the moment is that the relatively denser slab layer is actually quite soft and not very strong or cohesive compared to the weak layer underneath.  This snowpack still has the potential to become dangerous if we got a wet/heavy storm, but until then the avalanche danger will be isolated.  

Our snowpit tests indicated relatively good stability.  An extended column test revealed no tendency to propagate.  If someone were to venture into steeper wind loaded terrain, I wouldn’t be surprised to hear of reactive wind loaded pockets.  The main deterrent from going those places will be thin snowcover and exposed rocks rather than the avalanche conditions.  Click here for a more detailed writeup on the pit profile below.

Weather
Thu, November 28th, 2013

Turnagain Pass received roughly the same amount of snow yesterday as Anchorage did.  That 3-5 inches of light, dry snow certainly improved the surface conditions, but still leaves a lot to be desired in terms of adequate snow depth.  

It looks like our precipitation is shut off for the next few days.  We can expect colder temperatures by this evening, remaining in the single digits or teens for the rest of the holiday weekend.  Expect a moderate NW wind in the mountains today, 25-45mph.  Clouds today will give way to clear skies by this evening.  

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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.