Newly formed wind slabs may remain touchy on Saturday. Cornices are also large and weak.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Friday
Weather Forecast
A brief pulse will bring 5-12cm of new snow to the region on Friday night. Expect gradual clearing throughout the day on Saturday and mainly clear skies on Sunday. On Sunday night the region may see light flurries, but more clearing is expected on Monday. Ridgetop winds will be generally strong from the southwest with Friday and Sunday nights` systems; otherwise, they will remain mainly light. Freezing levels should hover between 1300 and 1500m for the forecast period.
Avalanche Summary
Recent avalanche observations have been extremely limited, mostly due to stormy weather. New wind and snow forecast for Friday night will promote a round of wind slab activity in high elevation lee terrain.
Snowpack Summary
New snow and wind forecast for Friday night will form new wind slabs in lee terrain at treeline and in the alpine. Up to 10mm of precipitation fell on Thursday. At treeline and in the alpine, precipitation fell as snow and strong southwest winds formed wind slabs. Throughout the storm the rain line trended from about 1750m down to about 1500m. Ongoing stormy weather has also encouraged new cornice growth. Many of these cornices are reported to be huge and unsupported. About 20-40cm below the surface you may find a melt freeze crust which formed during the 2nd week of February. At the same interface, you may find surface hoar which most likely exists on high, north facing terrain. Rain and warm temperatures have likely flushed out this weakness in most areas; however, continued reactivity may exist in high elevation terrain above the recent rain line. West of the divide, a layer of buried surface hoar can be found between 50 and 70cm below the surface. Recent reports suggest this layer has become less of a concern.
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.