January 23, 2018

Avalanche Danger Update

Issued at 12:30pm:

A few to several inches of new snow with light to moderate wind has increased avalanche danger in Chugach State Park.

Avalanche concerns include human triggered soft storm slabs (on terrain steeper than ~35* where the wind has consolidated the fresh snow into a slab – primarily in the upper elevations on wind loaded terrain features: cross-loaded gully sidewalls and near leeward ridge lines and peaks), loose snow sluffing (terrain steeper than ~35*), and persistent slabs (upper elevation areas with an actual snowpack – catchment areas with deeper snow like cross-loaded gullies and upper elevation leeward terrain features).

Observations across the park have revealed a generally thin snowpack (basically non-existent at lower and mid elevations) with poor structure, low strength, and potentially high energy.  This means that there’s the potential for relatively unpredictable human triggered persistent slabs that could release near the ground and produce avalanches that could bury, injure, or kill a person.

Open slopes that could produce wide propagation and slopes with terrain traps (that could compound the consequences of even a small avalanche) are very suspect and should be approached with a great deal of caution.

We are still not issuing regular informational products (advisories, observations) due to the thin snowpack; there’s not much snow below ~2500′ (basically scattered patches of old snow now covered by the few to several inches of fresh).  Above 3000′ there is generally adequate snow for riding, but avalanche danger (especially persistent slabs) and scattered thin snowpack hazards (exposed or shallowly buried rocks, vegetation, etc.) exist.

Prior to this storm there were widespread areas of standing and intact surface hoar and near surface facets.  Since today’s storm was not preceded by significant wind, it’s very possible that these persistent weak layers were preserved and buried.  Compounding this problem, much of the surface hoar and facets overlay relatively firm and low friction (potential bed) surfaces: windboard, melt-freeze, and rain crusts.

The snowpack setup in Chugach State Park is generally NOT benign; steep terrain should be approached with caution and investigated for stability thoroughly before a decision is made in regard to exposure.  Despite the snowpack seeming thin, there’s more than enough to avalanche in the upper elevations and the current state of the snowpack could produce a dangerous surprise.