North Columbia

Snowfall amounts and timing of the approaching snowstorm are uncertain. As storm totals approach 10 cm strong southwest winds will likely create shallow wind slabs.

Moderate - Timing, track, or intensity of incoming weather system is uncertain

FRIDAY NIGHT: Clear with cloudy periods and flurries / moderate west wind / alpine low -6 C / freezing level at valley bottomSATURDAY: Cloudy / 5-10 cm of snow accumulation / strong southwest wind / alpine high -5 C / freezing level 1600 mSUNDAY: Cloudy with sunny periods / 5-10 cm of snow accumulation / moderate west wind / alpine high -7 C / freezing level 1500 mMONDAY: Mix of sun and cloud / light southwest wind / alpine high -7 C / freezing level 1600 m

On Thursday, a few human triggered loose wet avalanches up to size 1.5 were observed on steep slopes in the afternoon. On Wednesday the avalanche activity decreased. A few natural and human triggered wind/storm slab avalanches up to size 2 were reported on west and north aspects at treeline and in the alpine.On Tuesday, several natural and human triggered storm/wind slab avalanches 20-40 cm deep and up to size 2.5 were observed on north and east aspects. Two of these were remotely triggered, one by humans and another one by a helicopter. A layer of small surface hoar below the most recent snow may have been the weak layer. Several natural wet slab and loose wet avalanches up to size 2.5 were reported from south and west aspects (see a MIN report from Glacier National Park).

The new snow likely falls on a melt-freeze crust on all aspects except for north facing slopes above 2000 m, where the snow has remained dry. Last weeks unsettled weather produced 30-50 cm of snow which is slowly bonding on northern aspects where it might sit on surface hoar (feathery crystals) in some areas. Older wind slabs sitting on surface hoar might still be sensitive to human triggers.Snowfall amounts taper quickly below treeline. Snow is disappearing rapidly at lower elevations.