Use caution at low elevations in the afternoon when the sun warms the recent storm snow, especially in areas that received more new snow.
Weather Forecast
Saturday: A ridge of high pressure builds and settles in. Expect mostly sunny skies, light northerly winds and alpine temperatures around -1.Sunday & Monday: The ridge continues to dominate. Expect continued sunny skies, light northerlies and high freezing levels in the afternoons.
Avalanche Summary
Reports continue of natural, explosive and rider triggered windslabs up to size 2.5 failing on northwest through east facing terrain. These are failing predominantly at treeline and in the alpine. Remote and accidental triggering have been observed. The south end of the region has seen the larger releases with wider propagation; at times linking terrain around ridge features. These areas have also seen storm slab events on open, convex features below treeline.
Snowpack Summary
The storm is over and a high pressure ridge is building in its wake. Storm snow amounts vary widely within the region, with 30cm in the north end of the region and up to 90cm at the south end. Consistent southerly winds during the storm period built windslabs in lee terrain and helped grow cornices.Newly buried surfaces (the Feb. 3 interface) include old windslabs, temperature and sun crusts. The new snow is bonding reasonably well at this interface in most locations with the highest concern being the bond to crusts on south and west facing terrain. The January 23rd interface (crusts, facets and surface hoar crystals) lingers in isolated locations. This layer seems to be rounding and bonding under current conditions, but we have reports of a recent size 2.0 releasing on this layer. The mid pack is generally well settled with the average snowpack depth at treeline around 180 cm.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.