Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Thursday
Weather Forecast
A ridge of high pressure will continue to keep the region dry through Tuesday. Ridgetop winds are light from the SE. Freezing levels near 1000m. The pattern will start to change on Wednesday afternoon. Light snow amounts are expected with freezing levels near 950m. Alpine temperatures could drop to -9, and treeline temps may hover near -3. Weather models seem to be conflicting with precipitation amounts for the outlook. Thursday may bring 2-4mm, accompanied by light NW winds.
Avalanche Summary
No new avalanche observations reported.
Snowpack Summary
Snow surface conditions are variable. Thin, breakable sun crusts are developing on steep solar aspects in the alpine. At treeline and below treeline surface faceting and surface hoar growth (5mm) are forming; especially on shady aspects in sheltered locations. In the Duffy Lake area the upper snowpack continues to settle and bond. Cornice fall is still a concern under the sunny skies and could trigger a large slab avalanche from the slope below. The Coquihalla sees similar surface crusts and crystal forms as the Duffy, but additionally has hard slabs 5-15cm thick due to strong outflow winds. The wind pressed surfaces and hard slabs all sit on a generally well settled upper snowpack. The older storm slab in the Coquihalla is about a meter deep and continues to settle and bond.
Problems
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.
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.