Avalanche Forecast

Tuesday Night: Snow, 10-20 cm, strong southwest wind, alpine high -4, freezing level 1400 m.

Wednesday: Flurries, 5-10 cm, moderate to strong west wind, alpine high -5, freezing level 1300 m.

Thursday: Cloudy with sunny breaks, light to moderate northwest wind, alpine high -8, freezing level 600 m.

Friday: Isolated flurries, moderate to strong southwest wind, alpine high -7, freezing level 600 m.

There was a report of several naturally triggered size 2.5 wind slab avalanches on north aspects on the south side of the highway corridor on the eastern side of Rogers Pass on Monday. Additionally explosive work on Monday produced wind slabs up to size 1.5. 

New snow accumulating Monday through Tuesday night has fallen on wind affected surfaces at upper elevations, surface hoar in wind sheltered areas and a thin crust on solar aspects. Winds are likely redistributing new snow into wind slabs and growing cornices. 

A couple of persistent weak layers exist in the upper to mid snowpack:

• The upper layer, found 40-80 cm down, is a spotty layer of surface hoar at treeline and below. 
• The lower layer, found 90-150 cm down, is widespread and can present as surface hoar and/or a crust.

Avalanche activity on these layers has dwindled since last week and snowpack tests results have generally indicated the weak layers are gaining strength. Incoming snowfall early this week will add additional load to these layers and may shed some light on whether they will remain a concern.

• Watch for newly formed and reactive wind slabs as you transition into wind affected terrain.
• Wind slabs are most reactive during their formation.
• Dial back your terrain choices if you are seeing more than 20 cm of new snow.
• Watch for signs of slab formation throughout the day.
• Expect slab conditions to change drastically as you move into wind exposed terrain.