Regions
South Coast Inland.
New snowfall may not bond well to underlying snow surfaces. Expect old and new wind slabs on all aspects at higher elevations, loose dry snow in sheltered areas, and looming cornices on ridgelines.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
FRIDAY: Cloudy with snowfall, accumulation 5 to 15 cm, strong southwesterly winds, alpine temperature -12 C, freezing level below valley bottom.SATURDAY: Cloudy with early-morning snowfall then clearing to partly cloudy, accumulation 5 to 10 cm, light northwesterly winds, alpine temperature -10 C, freezing level near 500 m.SUNDAY: Cloudy with early-morning snowfall, accumulation 5 to 15 cm, moderate to strong westerly winds, alpine temperature -7 C, freezing level near 700 m.
Avalanche Summary
No new avalanche observations were noted on Wednesday. On Tuesday, several natural loose dry avalanches up to size 1 were reported from steep south facing rocky terrain.Wind slabs are becoming more stubborn to trigger but remain the primary avalanche concern for the region. Respect overhead hazards, such as cornices.
Snowpack Summary
New storm snow will fall on highly variable and wind-affected snow surfaces. In exposed terrain, new snow will fall on scoured north facing slopes and wind-loaded south facing slopes. In sheltered terrain, new snow will fall on last weekend’s storm snow. The new snow may not bond well to these surfaces and could be reactive to both natural and human triggers.Deeper in the snowpack in southern parts of the region, recent snow sits above a widespread crust. Below the crust, well-consolidated snow exists.Avalanche professionals are still monitoring the mid-January crust and are avoiding shallow rocky slopes where triggering this layer is most likely. This layer is now 80-150 cm deep, but a heavy trigger (such as a cornice fall) or the next major storm (loading and/or warming) could wake this layer up.
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.