Regions
Northwest Coastal.
If solar radiation is strong and alpine temperatures are warm on Sunday, loose wet avalanches may occur on steep, sun-exposed slopes.
Confidence
Moderate - Timing or intensity of solar radiation is uncertain
Weather Forecast
Sunday will likely mark the last day of the dry ridge of high pressure. A temperature inversion is still expected with above-freezing temperatures and light ridgetop winds. On Monday and Tuesday, expect cool and unsettled weather with light flurries, moderate southeast winds and freezing levels at or near valley bottom.
Avalanche Summary
Aside from a few size 1 wind slab avalanches in the far north of the region, no new avalanches have been reported.
Snowpack Summary
Snowpack surfaces are highly variable. Temperature inversions and solar radiation have come into play, and depending on the time of day, sun-exposed slopes at higher elevations may be either moist or refrozen. On shaded slopes, 25-40 cm of storm snow from Boxing Day continues to facet, and new surface hoar has been reported at all elevations. In areas where recent winds have been light, shaded slopes will likely provide unconsolidated powder. In areas where winds have been stronger, reactive wind slabs may exist, especially in areas where the the slab overlies surface hoar buried by the boxing day storm.Professionals in the region are still keeping an eye on a few other surface hoar layers that developed throughout December which are now buried in the top 100cm. Although these layers may be gaining strength, they are worth keeping an eye on, especially on steep unsupported slopes at treeline and below. In colder and shallower snowpack areas watch for weak basal facets.
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.
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.