Regions
Northwest Inland.
We should see conditions start changing on Friday but I'm anticipating slow build. Avalanche danger could jump to considerable on Friday if the weather arrives early or with greater intensity than forecast.
Weather Forecast
Friday: Snow picking up throughout the day – 10-15 cm. The freezing level climbs to 1500 m in the south and 500 m in the north. Winds are crankin’ from the S-SW. Saturday: Cloudy with periods of snow and possible sunny breaks. The freezing level is between 1000 in the north and 1500 m in the south. Winds are strong from the S-SW. Sunday: Cloudy with flurries. The freezing level is around 1400 m lowering throughout the day. Winds are moderate to strong from the S-SW.
Avalanche Summary
No new avalanche activity reported. This could change on Friday with forecast snowfall, warming and strong winds.
Snowpack Summary
Persistent cold dry weather has resulted in significant new surface hoar growth and surface facetting on shady slopes at all elevations. Steep solar aspects may have a sun crust. The early February weak layer of facets, crusts, and surface hoar is buried down about 35-80 cm. The snow above the crust has been transported by Southwest winds and then reverse loaded by Easterly or Southeast winds. Cold temperatures have not settled the snow above the weak layer into a cohesive slab, and the cold has preserved the weak layer and associated crusts. Basal facets and depth hoar remain a concern in areas with thin or variable snow cover.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.