Regions
Northwest Coastal.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Wednesday: Light showers. Freezing level around 1500 m. Moderate southerly winds.Thursday: Light to locally moderate precipitation. Freezing level around 1400 m. Light to moderate north-westerly winds.Friday: Light precipitation, clearing by afternoon. Freezing level around 1200 m.
Avalanche Summary
Recent reports include wet loose avalanches up to size 2.5 in response to warming and sunshine. Large glide avalanches were also reported. On Saturday, a size 3 glide release removed trees and left a 4-5 m deep deposit near Shames. Last week, a large icefall triggered a slab in the Bear Pass area, creating a size 4 avalanche.
Snowpack Summary
Cornices and icefall are an increased concern now that spring is upon us. A melt-freeze crust exists on solar aspects and at low elevations. In some areas, limited overnight cooling has kept surface snow from re-freezing, leaving it loose and cohesionless. Forecast rainfall at low elevations may have a similar effect. Surface hoar has been reported on shady slopes up into the alpine. Dry settling or faceting snow can be found on high north aspects. Pockets of wind slab formed with recent easterly outflow winds. Glide cracks have opened up and pose the threat of full-depth releases, especially on steep rocky terrain features.
Problems
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
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.