Avalanche Forecast

Uncertainty is in actual snowfall amounts tonight and Wednesday.

Tuesday Night: Periods of snow 5-20 cm and rain. Forecast freezing levels near 1200 m. Alpine temperatures near -3 and ridgetop winds will be strong from the south-southwest.

Wednesday: Precipitation continues in the morning with 5-15 cm possible. Alpine temperatures near -2 and freezing levels around 1200 m. Ridgetop winds will be generally light from the South with strong gusts.

Thursday: A mix of sun and cloud with freezing levels dropping to the valley bottom and alpine temperatures near -10. Ridgetop wind will be light from the East.

Friday: Cloudy with some flurries. Strong easterly wind and freezing levels remain in the valley bottom.

No new avalanche observations were reported on Tuesday. If higher snowfall amounts accompanied by strong ridgetop winds play out overnight Tuesday and into Wednesday, I would expect to see some storm and wind slab avalanche activity at upper elevations. Loose-dry avalanches may also occur especially from steep terrain. 

Have you been out? If so, we would love to hear about it on the Mountain Information Network. A picture is worth a thousand words! Thanks for your submissions. 

Total snowfall amounts for Wednesday are still uncertain, however; we do know that the new snow will bury recently formed surface hoar (feathery, frost-like crystals). The strong southwest winds may have destroyed some of the surface hoar especially on wind-exposed slopes, but in wind-sheltered areas, the surface hoar may be alive and well unless the rain got to it at lower elevations. If the new snow accumulations add up, a reactive storm slab may exist, especially where it sits above surface hoar or a melt-freeze crust on solar aspects that formed during last week’s sunshine. Fresh wind slabs may be reactive on leeward slopes where the new snow deposits into deeper drifts. 

Deeper in the snowpack two predominant crusts exist from November. A widespread rain crust from early November that can be found up to 2500 m and buried down around 100 cm and a shallower one from late November down around 30 cm. These crusts have shown no recent reactivity in snowpack testing, however; given the stagnant weather pattern and a decreasing trend in instability, this problematic snowpack structure is not currently listed as a problem. This may change with increased load from new snow and wind and something to keep on your radar moving forward. We may see it transition to our problems page once we see it reach a certain threshold or receive information/ feedback that it’s waking up. The snowpack is thin and variable in wind-scoured areas, and it tapers rapidly at lower elevations. Snowpack depths at sheltered upper treeline elevations are nearing 100 cm and beginning to exceed the threshold for avalanches. 

• Storm snow and wind is forming touchy slabs. Use caution in lee areas in the alpine and treeline.
• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Closely monitor how the new snow is bonding to the old surface.