The hazard may be higher than forecast if snowfall amounts are larger than expected.
Confidence
Fair - Forecast snowfall amounts are uncertain
Weather Forecast
Synopsis: A slow moving frontal system will bring precipitation into BC.Tonight: Cloudy with flurries, some parts of the region may receive 20 to 30 cm of precipitation. No overnight freeze, freezing levels up to 1400m, Winds moderate, gusting to strong from the south west.Friday: Cloudy with flurries. Some parts of the forecast area may get up to 20 cm of precipitation. No overnight freeze and freezing levels may go up to 1600m. Winds moderate, gusting to strong from the south west.Saturday: Cloudy with flurries. 5 to 10 cm of precipitation in the forecast for the region, daytime freezing level around 1600m, overnight freezing level may drop to valley bottom in some parts of the forecast area, winds, light to moderate from the south west.Sunday: Cloudy with flurries. 5 to 10 cm of precipitation in the forecast, daytime freezing level around 1600m, no overnight freeze, winds, light to moderate from the south west.
Avalanche Summary
2 Reports of large natural avalanches on south east aspects and explosive testing is still producing large avalanches, ( size 2's and 3's) most stepping down to known persistent weak layers. We expect to see natural avalanche activity rise with snow and winds associated with the incoming storm system on Thursday and Friday, along with periods of sun and increased air temperatures later in the week.
Snowpack Summary
Up to 50cm of new snow has fallen in the central part of the region in the last storm, with lesser accumulations in the eastern part of the forecast region.. This new snow is settling well, but has also been formed into wind slabs on the lee sides of ridge crests by strong westerly winds.Numerous crusts can be found in the upper 60cm of the snowpack on south facing slopes. The March 15 crust/surface hoar interface is down approximately 50-80cm in most parts of the forecast area. At 90-120cm below the surface you may find surface hoar and crusts that were buried at the beginning of March. This interface is still touchy in some areas, particularly in the north of the region and continues to produce sudden planar failures in compression tests.The deeper facet/crust persistent weakness buried at the beginning of February, now down 120 - 200cm, has proven to be reactive and should not be trusted. An avalanche on any of these deeper, persistent interfaces would be large and destructive. Weak basal facets exist in many areas, but without a large load, triggering is unlikely.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.