Stormy weather continues, bringing extreme winds and up to 90 mm of precipitation as rain or snow by Monday afternoon.
Travel in avalanche terrain is not recommended.
A crust / facet layer from mid-November was buried 50 to 100 cm before this storm. Storm slabs have potential to step down to this layer making very large avalanches.
Up to 90 mm of precipitation combined with strong to extreme southwesterly winds is building widespread thick and reactive storm slabs above the rain/snow line.
Last Wednesday, a very large size 3 avalanche stepped down to a persistent weak layer near Allison Pass. Several wet loose avalanches also occurred, see photo captions for more details.
Looking forward, as another atmospheric river brings significant precipitation, we can expect to see more large avalanches occurring.
50 to 90 mm of precipitation, combined with strong to extreme southerly winds, is forecast to fall by 4 pm Monday. We expect to see widespread reactive storm slabs building as a result.
The snow/rain line elevation is uncertain and expected to fluctuate during the storm. It's possible we could see rain up to 2100 m. There is potential for wet loose avalanches where the snow surface is wet.
A crust with facets, formed in mid-November, was buried 50 to 100 cm before the storm. Storm slabs have the potential to step down to this layer, causing very large avalanches.
Total snowpack depths range from 80 to 140 cm deep at treeline, and diminish rapidly below 1500 m.
Sunday Night
Cloudy. 10 to 30 mm of precipitation as rain or snow at treeline. 50 km/h southwest ridgetop wind. Treeline temperature 2 °C. Freezing level 2000 m to 2400 m.
Monday
Cloudy. 40 to 60 mm of precipitation as rain or snow at treeline. 70 km/h southwest ridgetop wind. Treeline temperature 3 °C. Freezing level 1900 m to 2500 m.
Tuesday
Mostly cloudy. 20 to 30 cm of snow. 50 km/h southwest ridgetop wind. Treeline temperature -3 °C. Freezing level 1200 m to 1400 m.
Wednesday
Mostly cloudy. 30 to 50 cm of snow. 50 km/h west ridgetop wind. Treeline temperature -6 °C. Freezing level 1000 m.
More details can be found in the Mountain Weather Forecast.
