Newly formed winds slabs will present a high hazard for some time. Careful route selection is critical at this time
Confidence
Fair - Due to the number and quality of field observations
Weather Forecast
A Pacific frontal system will pass through the extreme southern portion of BC today ( Sunday) and into early Monday leaving us with 10 to 20cm of snow at higher elevations and rain below1200m. Moderate to strong winds above 1500m will accompany this system. Tuesday should see some clearing skies and very light precipitation late in the day, then more clearing for Wednesday.
Avalanche Summary
1 size 2 storm slab observed on a NW aspect in steep alpine terrain. Limited observations from yesterday due to low ceilings and poor visibility.
Snowpack Summary
10 to 20cm of recent storm snow now lies on a variety of crusts and old wind slabs above treeline. A crust that was beginning to break down and facet was buried around March 5 and may be the one to look for in the snowpack. Much of the new snow will have been redistributed by strong winds during parts of the storm. Below treeline the snowpack has had numerous warming and rain events and should be bombproof for the most part. Rain has recently been reported to ridge tops in the Coquihalla region. Solar aspects have been reported as isothermal in some areas below 1600m.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.