Regions
Northwest Inland.
Strong easterly winds on Tuesday-Wednesday may result in unusual snow loading patterns. Cornices are large and remain a significant concern.
Confidence
Low - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Light precipitation and STRONG easterly winds on Tuesday-Wednesday. Unsettled weather and cool temperatures thereafter. WEDNESDAY: Mix of sun and cloud with occasional flurries (5-15cm possible). Strong easterly ridgetop winds. Freezing level around 1500 m.THURSDAY: Mainly cloudy with isolated flurries (2-5cm). Moderate southeasterly ridgetop winds. Freezing level around 1400 m.FRIDAY: Cloudy with scattered flurries (3-5cm). Light southerly ridgetop winds. Freezing level around 1300 m.
Avalanche Summary
On Monday, several loose wet avalanches to Size 2.5 were reported in the afternoon with solar input in the north of the region. Also in the north, a cornice failure on a northwest aspect resulted in a slab avalanche, Size 3.0.
Snowpack Summary
Small amounts of new snow (3-10cm) fell in the past three days. Winds were light to moderate (south through northeast) and may have created small wind slabs on lee features below alpine ridgetops. The new snow will likely be sitting on hard surfaces created by strong winds last week.Elevations below roughly 1300 m are experiencing a daily melt-freeze cycle and the snowpack is likely isothermal. The February crust and facet layer is 70-90 cm deep in the Houston Telkwas sled area and a deep persistent faceted weak layer is still lingering near the bottom of the snowpack in all areas.
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.