January 13, 2015

The never-quite-winter continues…

Avalanche Concerns:

If you’re venturing into the mid to upper elevations of Chugach State Park in the near future, you will need to (as you always should) rely on your own assessment of snow and avalanche conditions.  With a high degree of snowpack spatial variability across the park, combined with recent wind and temperature variability, avalanche concerns are also currently quite variable.

Be on the lookout for snow that is becoming gloppy and saturated (WET!).  Wet loose avalanches may be possible where temperatures are warmer and have remained above freezing.  While they’ll likely be small, they can entrain more snow as they descend and can become even more dangerous if they’re funneled or channeled by the terrain.  Be mindful of exposure and terrain traps.  While less likely, wet slab avalanches aren’t completely out of the equation.  These will be larger and more dangerous.  They could fail deeper in the snowpack on persistent weak layers or at other snow layer interfaces where melt water has percolated.

In deeper, higher, and colder areas of the park; be on the lookout for the typical red flags of avalanche instability.  Be mindful of fresh wind slabs, the lurking persistent weak layers, and persistent slab avalanches.

There’s bad news and good (relatively speaking) news:

Treacherously icy roads (i.e. risk to AAC volunteer staff’s personal vehicles), unpleasant to dangerous backcountry travel conditions, strong winds, and lack of public backcountry traffic in the mid to upper elevations of Chugach State Park are some of the many factors that have hindered gathering the observations necessary for providing a thorough assessment of backcounty snow and avalanche conditions recently.

Temperatures warmed to above freezing to at least 4000′ in areas of Chugach State Park last week, then cooled to below freezing.  While the initial warmup elevated the avalanche danger and likely destabilized persistent weak layers and possibly even caused some wet avalanche activity, the warm temperatures decreased the temperature gradient in the thin snowpack (contributing to a more benign snow metamorphism) and the subsequent re-freeze had a further stabilizing effect.

However, temperatures have once again warmed above freezing in the mid to upper elevations (2000-4000+’ in areas).  At the mid to upper elevations in at least some areas of the advisory zone, temperatures up to 4000′ have remained above freezing for ~24 hrs.  This is once again contributing to a destabilizing effect, although it won’t be as dramatic as the initial warming shock that occurred last week.  On the bright side, once temperatures become consistently cooler and stay below freezing (possibly by this weekend) the snowpack will re-stabilize and the thaw-freeze cycle will have helped to heal the dangerous persistent weak layers that have been plaguing the Chugach State Park snowpack.

While winds in many areas have been strong for extended periods of time during the past week, there hasn’t been much loose snow available for transport and this has limited the development of dangerous wind slabs.  However, there has likely been some new snow at higher elevations (above ~4000′) and strong winds have likely created some localized to isolated wind slabs.  While these may be reactive, the warm temperatures have likely contributed to bonding and they should stabilize relatively quickly.

As for the weather, the Anchorage National Weather Service office reported this morning: “WINTER IS NOWHERE IN SIGHT FOR SOUTHERN ALASKA.  THE RECORD BREAKING WARM WINTER MARCHES ON…”

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