Confidence
Fair - Track of incoming weather is uncertain on Sunday
Weather Forecast
Synopsis: A frontal system is forecast to move through on Friday night, followed closely by another system on Saturday night. Conditions should begin to dry out later on Sunday and Monday as a brief ridge of high pressure forms. Tonight and Saturday: 15-20 mm of precipitation, easing off in the afternoon. The freezing level is around 1500 m, lowering in the wake of the system. Winds are moderate from the south-southwest. Sunday: Moderate precipitation is possible but confidence on Sunday is low. Some models show the bulk of the precipitation heading south of the border. Temperatures continue to cool slightly. Monday: Drier conditions are likely. The daytime freezing level could rise to 1800 m, especially if the sun makes and appearance.
Avalanche Summary
There were no reports of new avalanches on Thursday. One recent size 3 wet slab was observed in the backcountry near Whistler on Wednesday. This slide occurred on a south facing slope.
Snowpack Summary
Up to 50 cm of moist or wet new snow sits on the previous snow surface, which included a melt-freeze crust, moist or wet snow, or pockets of surface hoar. Recent snowfall amounts vary considerably with elevation due to fluctuating freezing levels. Dense new wind slabs are likely in exposed lee terrain at and above treeline. The upper snowpack at lower elevations has become isothermal from recent warm temperatures and rain. Cornices are very large and could pop off with continued mild temperatures or during periods of sun.
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.