North Columbia

Evaluate snow and terrain carefully at upper elevations where both persistent and wind slab avalanches are possible.

A few small (size 1) wind slab and dry loose avalanches were triggered by riders and explosives on Tuesday. With incoming snow and wind on Thursday, small avalanches in the surface snow will likely continue. Triggering a persistent slab avalanche remains possible in upper treeline and alpine terrain.

New snow is gradually accumulating over crusts, surface hoar, and facets that were buried a few days ago. Amounts above this interface vary from 5 to 25 cm, and reports suggest it may be bonding poorly. A crust formed by a December rain event is found roughly 60 cm deep, and a layer of surface hoar is found 60 to 100 cm deep. Where it exists, the crust makes it harder to trigger the surface hoar layer, but triggering remains a concern at higher elevations where the crust is less prominent. The lower snowpack is variable throughout the region, with basal facets possible in shallower snowpack areas.

Wednesday Night

Cloudy with 0 to 1 cm of snow, alpine wind southwest 30 km/h, treeline temperature -5 °C.

Thursday

Cloudy with 3 to 8 cm of snow, alpine wind southwest 40 km/h, treeline temperature -5 °C.

Friday

Cloudy with 3 to 8 cm overnight then partly cloudy in the afternoon, alpine wind west 30 km/h, treeline temperature -7 °C.

Saturday

Cloudy with 5 to 15 cm of snow, alpine wind south 50 km/h, treeline temperature -8 °C.

More details can be found in the Mountain Weather Forecast.

• Carefully assess open slopes and convex rolls where buried surface hoar may be preserved.
• Watch for wind-loaded pockets especially around ridgecrest and in extreme terrain.
• Closely monitor how the new snow is bonding to the old surface.