North Columbia

New snow combined with wind is promoting continued wind slab development in the alpine and treeline.

Moderate - Forecast snowfall amounts are uncertain on Thursday

WEDNESDAY NIGHT: Mainly cloudy with flurries, accumulation of 5-10 cm, moderate southwest winds, alpine temperature -6 CTHURSDAY: Isolated flurries, moderate southwest winds, alpine temperature -3 C, freezing level 1200mFRIDAY: Cloudy with sunny periods, light to moderate southwest winds, alpine temperature -3 C, freezing level 1300 mSATURDAY: Mix of sun and cloud, light southwest winds, alpine temperature 1 C, possible temperature inversion

A size 3-3.5 persistent slab avalanche was skier triggered on the north side of the highway in Glacier National Park on Tuesday. This was triggered from a thin spot on the ridge at 2250 m on a south east aspect It ran to the valley bottom and is suspected to have run on a layer of surface hoar sitting on a crust that was buried in late November. See the MIN post here.

Snowfall combined with wind on Wednesday into Thursday will have formed new wind slabs in lee and cross-loaded terrain features at high elevations. This new snow has fallen on widespread wind-affected snow at alpine and treeline elevations. Below this, the snowpack is generally well-settled. There is however, a layer of feathery surface hoar that is sitting on a crust that was buried late November down 100-200 cm. This crust is suspected to be the bed surface for few very large avalanches over the past several days on southwest through southeast aspects in this region.