Snowfall amounts are uncertain but the storm wont fizzle out until Wednesday night. Expect reactive storm and wind slabs Tuesday and Wednesday. Bump the danger to HIGH if your local riding receives 25 cm or more of new snow.
Storm slabs will build overnight Monday through Wednesday. Watch for fresh sensitive slabs on all aspects. Reactive and deeper wind slabs may exist on leeward slopes as the strong southwest wind transports the new snow.
A frontal system will move through the region Monday and into Tuesday bringing more snow and sustained ridgetop wind.
Monday Night: Snow amounts 5-10 cm. Ridgetop wind strong from the southwest and freezing levels valley bottom. Alpine temperatures near -15.
Tuesday: Snow amounts near 10 cm. Ridgetop wind strong from the southwest and alpine temperatures near -12.
Wednesday: Another 5-10 cm of new snow expected. Ridgetop wind moderate from the southwest.
Thursday: Mostly cloudy with ridgetop wind easing to light values. Alpine temperatures holding -15.
On Sunday, a snowmobile triggered size 2 slab avalanche was reported from a south-facing route to the lake above the Fraser camp.
As the snow and wind pick-up Monday night, storm and wind slab avalanches will likely be reactive on Tuesday and Wednesday.
The snowpack throughout the region shows a lot of variability, which means these fresh slabs may be more reactive in some areas and less in others.
Up to 35 cm of snow fell over the past week. The next system starting Monday evening could bring another 20 to 30 cm by Wednesday, accompanied by a strong southwest wind. Building storm slabs will likely be reactive, especially where it sits above a sun crust on solar aspects. Fresh wind slabs may also be reactive on leeward slopes due to the consistent strong southwest wind.
The snowpack inland (between Wheaton and White Pass) is currently complex due to variability. A weak layer of buried (feather-like crystals) surface hoar has been seen in glades and gullies that are sheltered from the wind and buried 40-60 cm down. Whumps and cracking have been felt and seen beneath the skis. In other locations, a stiff slab sits above weak (sugary) faceted crystals, while some locations are showing a bomber snowpack. VARIABLE!
Check out this recent local MIN Report from Saturday expressing this.
The Wheaton's continental snowpack is dominated by sugary facets and depth hoar, the icing is either layers or a fat cap of harder cohesive slab. It's an untrustworthy structure that requires really good terrain selection and travel habits, or a healthy dose of luck.
