North Columbia

Sustained strong winds are expected to quickly redistribute Thursday night's snowfall into touchy new wind slabs. Seek out sheltered lower elevations on Friday.

Moderate - Forecast snowfall amounts are uncertain

Thursday night: Cloudy with flurries bringing 5-10 cm of new snow. Moderate to strong southeast winds shifting to southwest.Friday: Cloudy with continuing scattered flurries bringing approximately 5 cm of new snow, continuing overnight. Moderate to strong southwest winds. Freezing level to 1000 metres with alpine high temperatures around -9.Saturday: A mix of sun and cloud. Light southwest winds. Freezing level to 1000 metres with alpine high temperatures around -9.Sunday: Mainly cloudy with isolated flurries and a trace of new snow. Light southwest winds. Freezing level to 1000 metres with alpine high temperatures around -10.

Reports from Wednesday included a couple of smaller (size 1-1.5) ski cut and skier-triggered storm slabs failing on one of the recently buried weak layers mentioned in our snowpack discussion, down 20 cm. These occurred on northwest and west aspects in the alpine.Reports from the weekend and earlier this week included several small (size 1) storm slab releases, mainly skier-triggered on steeper north to northeast-facing slopes in the alpine. A couple of larger (size 2) natural storm slabs were observed in very steep terrain during the warmest part of the day. These slabs are mostly suspected to have failed on a layer of surface hoar buried earlier this month that is mentioned in our snowpack discussion, found down about 30 cm. Looking forward, avalanche danger will be increasing as strong southeast (then southwest) winds and light snowfall form new slabs over Thursday night. These newly formed slabs are likely to be touchy and reactive to human triggering over the near term. The convective nature of forecast snowfall suggests that localized pockets of enhanced precipitation will lead to increased avalanche danger in parts of the region.

Recent light snowfalls have been followed by warm daytime temperatures and glimpses of sun, setting up a couple of thin storm snow layers over temperature and sun crusts at lower elevations and on south aspects. On shaded aspects at higher elevations, these snowfalls have buried and preserved a couple of surface hoar layers now found up to 30 cm deep. The deepest of these surface hoar layers has been the failure plane in several recent slab avalanches.New snow amounts taper with elevation and below 1800 m, minimal accumulations have buried a supportive crust on all aspects. This crust will likely break down with daytime warming, becoming moist in the afternoon. Deeper persistent weak layers from January and December are generally considered dormant, but could wake up with a surface avalanche stepping down, large cornice fall, or a human trigger in a shallow or variable-depth snowpack area. These layers consist of sun crust, surface hoar and/or facets.