Forecast snowfall amounts for Wednesday night and Thursday are highly variable throughout the region. Pay close attention to how much snow falls in your area, and be prepared to back off to simple terrain.
Confidence
Moderate - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
Moderate to locally heavy snowfall is forecast for Wednesday night. The Whistler area may see up to 15cm of new snow while double that amount may fall at the south end of Garibaldi Park and up the Squamish Valley. Generally light snowfall (up to 10cm) is forecast for Thursday; however, the convective nature of the weather pattern suggests spring "power flurries" may result in localized accumulations of up to 20cm. A dry ridge should develop on Friday bringing mainly clear skies while overcast conditions are expected on Saturday. Ridgetop winds should be moderate to strong from the southwest on Wednesday night and Thursday, and then become light for Friday and Saturday. Daytime freezing levels are forecast to sit at 1000m on Thursday, 1600m on Friday and 1400m on Saturday.
Avalanche Summary
On Tuesday natural loose wet avalanches to size 1.5 were reported to have occurred on variety of aspects and elevations. Forecast cooling should limit ongoing loose wet avalanche activity; however, a round of natural storm slab activity is expected on Thursday in response to new snow and strong southwest winds.
Snowpack Summary
Warm temperatures and the "greenhouse effect" from cloudy skies on Tuesday have promoted significant settlement within the recent storm snow. Dry settled powder can be found on high, north facing slopes while classic spring melt-freeze conditions exist on solar aspects above 2000m and all aspects at lower elevations. Potentially deep storm slabs are expected to form on Wednesday night and Thursday morning. Below the new snow the snowpack is strong and well-settled throughout with no notable persistent weaknesses. Cornices are huge and fragile.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.