Snow and strong wind Tuesday evening into Wednesday will likely form fresh storm and wind slabs at upper elevations. There is uncertainty with forecast snowfall amounts. If local snow amounts overnight are greater than 25 cm then avalanche danger will be High.
A couple of weak layers exist in the mid snowpack, buried 40-80 cm and 90-150 cm below the surface. They are highly variable in form and distribution and there has not been any associated avalanche activity in the last few days. Incoming snowfall in the forecast for this week will add additional load to these layers and may shed some light on whether they will remain a concern.
New snow and strong winds are likely forming fresh storm and wind slabs at upper elevations. Expect to find deepest deposits in lee terrain.
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:
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.
