North Columbia

A buried persistent weak layer may roar back to life over the next few days as the freezing level rises and the sun comes out. South facing slopes are especially suspect and are best avoided at this time.

Moderate - Timing or intensity of solar radiation is uncertain

Continued snowfall is expected Saturday night as an unstable air mass fuels convective precipitation. A ridge is expected to build offshore Sunday allowing the entire province to dry out. A more spring-like pattern begins to take shape on Monday with freezing levels creeping towards 2500 m by Tuesday.SATURDAY NIGHT: Overcast, freezing level around 1000 m, light to moderate west/southwest wind, 5 to 10 cm of snow possible. SUNDAY: Broken cloud cover, freezing level beginning around 1000 m rising to about 2000 m, light to moderate northwest wind, 1 to 5 cm of snow possible. MONDAY: Scattered cloud cover, freezing level beginning around 1500 m rising to about 2000 m, light west/southwest wind, no snow expected. TUESDAY: Scattered cloud cover, freezing level beginning around 1500 m rising to about 2500 m, light to moderate south/southwest wind, no significant precipitation expected.

A size 1.5 persistent slab avalanche with a 60 cm crown was skier triggered on a north facing slope at 2000 m. Natural loose dry and loose wet avalanches were observed on north and west facing slopes above 2000 m.On Thursday warming temperatures initiated large loose wet avalanches to size 3 on south facing aspects between 2100 and 2700 m in the neighboring Glacier National Park. A small shallow wind slab was accidently triggered by a skier on a steep/unsupported east/southeast facing feature at 2200 m too.

Saturday's new snow is coming to rest on a weak surface crust that exists on all aspects aside from true north below 2000 m. This crust extends up to around 2500 on south facing slopes. On north facing slopes above 2000 m, temperatures have remained cold and the snowpack is still quite "winter-like." Warming temperatures and time have helped to settle the upper 30 to 40 cm just below the surface.The main concern is the mid-March Persistent Weak Layer (PWL) which is now 60 to 100 cm below the surface. This layer is composed of a crust on all aspects at low elevations. At upper elevations the layer presents as a crust on solar aspects (those that face south and west) and buried surface hoar on polar aspects (those that face north and east). The reactivity of this interface has been steadily decreasing and while the likelihood of triggering a deeper persistent slab avalanche is lowering, the consequence of doing so remains high. Solar aspects are expected to be the most suspect as the freezing level begins to rise over the next few days.Deeper persistent weak layers from January and December are still being reported by professional observers, but are generally considered dormant.