Avalanche Forecast

The most significant loading from new storm and wind slab will occur late Thursday afternoon through Friday morning.   The new storm snow and wind deposited snow is expected to bond poorly to the variety of existing snow surfaces.  Natural avalanche activity will likely be limited by the amount of loading on the newly buried weak layers.  In areas that receive more wind transport and loading, such as the Mt. Baker area, expect a higher likelihood of natural avalanches.  Continued light showers and a warming trend during the day Friday will continue to stress the underlying snow. 

The snowpack is expected to be sensitive on Friday.  If venturing out into the backcounty on Friday, conservative trip planning and decision making in the field will be essential for safe travel. No reports of the quality or sensitivity of the bonding between new to old snow surfaces were available at the time of this forecast. 

The most recent storm cycle occurred in early December with most NWAC stations receiving copious amounts of precipitation, mainly in the form of rain at mid and lower elevations followed by a sharp cooling trend and generally 1-2 feet of snow for the west slopes at high and mid elevations. This storm cycle created a strong and generally thick rain crust with cohesionless new snow above the crust and produced little avalanche activity. 

A dry and very cold period followed with two bouts of wind, first strong easterly ridge top winds last Friday and Saturday and then winds shifted to strong west to northwesterly on Sunday and Monday, transporting loose surface snow and building small and isolated wind slabs on a variety of lee slopes.  A shallow wind slab was triggered on East Peak near Crystal Mountain on Sunday. 

The dry and cold stretch produced widespread reports of thick surface hoar growth, near surface faceted snow and of the strong crust breaking down due to strong temperature gradients within the upper snowpack.

Heading into the Thursday afternoon/night weather system, a variety of snow surfaces are present including isolated areas of shallow wind slab and scoured or icy surfaces at higher elevations near ridges, hoar frost near and below treeline, and near surface facets or powder on sheltered slopes and at lower elevations. Thin sun crusts have also been reported on steeper solar aspects.