Heavy precipitation, wind, and rising freezing levels are expect Monday night and Tuesday. High alpine areas will receive snow while at lower elevations a mix of heavy snow and rain are expected. Avalanche activity will increase with the storm.
Confidence
Moderate - Freezing levels are uncertain
Weather Forecast
There is uncertainty with freezing levels and how much precipitation will fall as rain/snow up to treeline. Alpine areas will likely see heavy snowfall.TONIGHT: Snow and rain. Precipitation 25-35 mm. Ridge wind moderate to strong, southwest. Temperature at treeline near 0. Freezing level 1200 m.TUESDAY: Snow and rain. Precipitation 5-15 mm. Ridge wind moderate, west. Temperature at treeline near 0. Freezing level rising to 1700 m.WEDNESDAY: Mix of sun and cloud. Ridge wind light, northwest. Temperature at treeline near -3. Freezing level 1000 m.THURSDAY: Cloudy, flurries. Accumulation 5-10 cm. Ridge wind light west. Temperature at treeline near -1. Freezing level 1200 m.
Avalanche Summary
Ski cutting on the North Shore mountains on Monday morning produced widespread size 1 storm slab releases on all aspects within the recent storm snow.Reports from the northern part of the region around Squamish over the weekend indicate that a natural avalanche cycle occurred in steep and convex alpine terrain with last week's storm.Expect natural activity to continue with the new storm load, rain, and rising freezing levels on Tuesday.
Snowpack Summary
The North Shore mountains received 25-30 cm overnight on Sunday and another 10-15 cm throughout the day on Monday, bringing storm snow totals to around 60-80 cm since last Thursday which is generally bonded well to the old surface up to treeline elevations.Alpine areas around Squamish have likely received about 60-100 cm of storm snow and more wind. In these areas the storm snow is likely sitting on a mixture of weak grains including a crust on solar aspects and potentially facets/surface hoar on polar aspects. Below the storm snow the snowpack is generally well settled and strong.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-slabs that form over a persistent weak layer (surface hoar, depth hoar, or near-surface facets) may be termed Persistent Slabs or may develop into Persistent Slabs.