Regions
Northwest Inland.
Confidence
Fair - Intensity of incoming weather is uncertain
Weather Forecast
Monday: light to moderate snowfall - strong southeast winds - freezing level at 1200m Tuesday: light to moderate snowfall - moderate southerly winds - freezing level at 700m Wednesday: light snowfall - strong southwest winds - freezing level at 850m
Avalanche Summary
Natural icefall initiated a small slab avalanche on Saturday. In the north of the region, sluffing was observed in steep terrain in the alpine and at treeline. No other avalanches were reported. We should see an increase in wind slab avalanche activity with forecast weather on Monday.
Snowpack Summary
Light amounts of recently fallen snow overlie previously formed wind slabs. In general, north aspects at higher elevations hold dryer, low density snow while melt/freeze conditions exist on solar aspects in the alpine and all aspects at treeline and below. Solar aspects are becoming moist and unstable under sunny skies. The mid-pack is generally well consolidated; however, the mid February persistent weak layer, comprised of spotty surface hoar, facets and crusts, is buried 80-120 cm below the surface. No recent activity has been reported on this interface. It most likely needs a large trigger on a specific spot. If an avalanche occurs on this weak interface it will be very large and destructive. Below this the snowpack is well settled and strong. Cornices in the area are reported to be very large. Cornice failure could trigger an avalanche on the slope below. On a side note, surface hoar growth has been noted in recent days and should be something to watch as new snow falls.
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.