January 22, 2015

Avalanche danger in Chugach State Park will be on the rise through Friday, and possibly into Saturday.  A winter weather advisory is currently in effect from 4pm today through 6am Saturday with 5-11 inches expected in town, which likely means significantly higher accumulations in the mountains.  Wind are forecast to be light, but this is questionable and winds will likely contribute to some areas being more heavily loaded than others.

The pre-storm snow surfaces in the mid to upper elevations of the park are a mixed-bag of varying crusts, dense snow, and some exposed ice.  Surface hoar may exist in areas, especially those more sheltered from the wind, and faceting at and near the surface has been extensive.  These weak snow grains, crusts, and dense slabs that will underlie the new snow will provide for weak layers and weak interfaces susceptible to human, and possibly naturally, triggered avalanches.

New snow, or storm snow, instabilities at the new-old snow interface are expected to be the primary avalanche concern through this weekend.  This will include loose snow avalanches, or sluffs, and storm slabs.  However, persistent weak layers (depth hoar, surface hoar, and faceted layers) remain deeper in the snowpack and may be more susceptible to triggering given the additional load of new snow.  The warm weather of last week followed by the subsequent re-freeze did contribute to stabilization of these potentially dangerous layers, but it did not eliminate them as a concern.  On the contrary, they may now be harder to trigger but potentially more disastrous: a low probability but high consequence scenario.

As for the new snow instabilities; be on the lookout for red flags and obvious signs of instability like recent avalanches, cracking, collapsing, “whumphing” sounds, and areas that have been more heavily loaded by the wind and appear fat/bulbous/pillowy or have a denser, textured surface with a hollow feel.  These clues are the mountains’ way of signaling danger!

It will be VERY IMPORTANT to approach the mountains with caution and respect during and immediately following this storm.  You will need to take the time to conduct your own local assessment of snow and avalanche conditions, and make your travel decisions accordingly.  Digging in the snow, analyzing layers, and conducting stability tests will be especially important for assessing the dangers of deeper persistent slab avalanche problems associated with the aforementioned persistent weak layers.

Please remember, the information provided by the Anchorage Avalanche Center is no substitute for an adequate level of experience and knowledge necessary for traveling through avalanche terrain safely.  It is only a reference point, a single piece of a complex puzzle, and is meant to help enhance your awareness.

Anchorage Avalanche Center staff will be participating in a demanding professional development opportunity for the next week.  It is likely that there will be no further updates until the beginning of February, but efforts will be made to provide pertinent information as best possible.

If you are out in Chugach State Park, please let us know what you’re finding in regard to snow and avalanche conditions.  PLEASE submit your observations!

Play safe out there and enjoy the new snow!!

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