Recently formed wind slabs may become reactive with solar radiation on Wednesday. Keep an eye on the sun and analyze each slope for patterns of wind effect before choosing your line.
Confidence
High - The weather pattern is stable
Weather Forecast
Wednesday: A mix of sun and cloud with no new snow. Winds moderate from the northeast. Possible alpine temperature inversion bringing alpine temperatures to -5.Thursday: Mainly cloudy with no new snow. Winds light from the west. Alpine temperatures of -6.Friday: Mainly cloudy with scattered flurries bringing up to 5cm of new snow. Winds moderate from the southwest. Alpine temperatures to -8.
Avalanche Summary
Two natural Size 1.5 wind slab avalanches with 40cm deep crowns were observed occurring southwest of Whistler on Monday on steep southwest and southeast slopes. Explosives testing in the Whistler area on Monday successfully targeted several reverse loaded pockets of wind slab in the alpine to Size 1.
Snowpack Summary
Between Monday and Friday last week, 70-100 cm of storm snow accumulated in the region. The critical part of snowpack analysis under current conditions is figuring out how the wind is redistributing this snow into wind slabs. Recent extreme northerly winds have "reverse loaded" much of the new snow onto southerly slopes that were previously scoured. Moderate northerly winds continued to promote this wind slab formation into Tuesday. The existence of wind slabs on solar aspects is important to note as clear skies will allow for strong solar radiation to affect these aspects. Below the new snow from last week lies the Boxing Day interface which consists of wind affected surfaces, faceted (sugary) snow, or surface hoar. Recent observations suggest the overlying snow is generally well bonded to this interface. The mid-December interface is now down 100-150 cm and is generally considered to be stable in this region. Snowpack layers below this are well bonded.
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.