Confidence
Fair - Due to limited field observations
Weather Forecast
Cool dry air out of the north brings light convective flow to much of the province Friday & Saturday. Friday: Sunny periods in the morning give way to broken cloud in the afternoon. Expect the occasional convective burst of snow. No significant precipitation is expected. Ridge top winds moderate out of the NW. Freezing level tops out around 1800 m. Saturday: Freezing level starts at the surface, climbs to 1700 m, then returns to the surface overnight. Winds moderate westerly at all elevations.. Sunday: Flow switches from north to south Saturday evening resulting in slightly warmer temps Sunday. Freezing level climbs to around 2000 m. Winds light out of the east at treeline, moderate W at ridge top.
Avalanche Summary
No avalanche activity reported from the region Wednesday or Thursday. Control work in the Fernie area Thursday produced avalanches to size 2 with most activity being limited to the 20 cm of storm snow. The storm snow was reportedly quite sensitive to ski cutting, numerous size 1.5 avalanches were triggered in this fashion on N, NE & E facing slopes. A few deeper avalanches were triggered by control work under headwall features too.
Snowpack Summary
10 - 20 cm of snow fell in the region Wednesday. The new snow was accompanied by moderate winds out of the south which created soft slabs on lee aspects. There was a good re-freeze reported from Monday night and again on Tuesday night, that has resulted in a supportive melt-freeze crust on all aspects up to about 2200 metres. North aspetcs may be dry down to about 2000 metres in some areas. Southerly aspects became moist in the alpine on Tuesday, but snowballing and wet point releases were limited to size 1.0. Forecast new snow and strong winds are expected to create new windslabs and add a new load to storm slabs. Deep weak layers may continue to be triggered by large loads like cornice falls or storm slab avalanches.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.