Think twice before getting on a steep alpine face today. Large avalanches are still possible.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Temperatures are very warm (freezing level peaking near 2700 m) on Thursday and Friday, before cooling on Saturday with the passage of a cold front. Light precipitation is expected on Friday, followed by 5-10 mm precipitation on Saturday. This tapers to flurries on Sunday. Winds are light to moderate SW, changing to NW on Saturday as the front passes through.
Avalanche Summary
Natural avalanche activity has been tapering since last weekend's storm cycle, but skiers and explosives were still producing large avalanches on Wednesday: A skier triggered a size 2 persistent slab avalanche on the mid-Jan layer in the Dogtooth range and went for a ride. Explosives also triggered a size 3 slab which started with a cornice failure, then ripped out to ground. Explosives triggered a size 2.5 avalanche on the November crust/facet layer in an area that had previously slid and then reloaded. A very large natural slab was also observed just outside the region near Invermere (look for the blue pin on the bulletin regions map to get the full report). Clearly the snowpack is still capable of producing destructive avalanches, so tread carefully.
Snowpack Summary
At high elevations, 40-60cm of rapidly settling snow sits over the late-Jan crust/surface hoar layer. Rain has recently soaked the snow surface up to around 2000m and moist snow is reported to at least 2200m. Overnight cooling may be forming a weak surface crust at some elevations. Strong SW winds have left wind slabs on lee alpine features. The mid-January surface hoar is typically down 50-80cm and has been very reactive in some areas. The mid-December weak layer is down around 1m but its reactivity has been isolated recently. The mid-November weak layer of crusts and facets can still be found near the bottom of the snowpack. It has generally been unreactive but one explosive triggered avalanche occurred on it recently in a reloaded area that had slid previously.
Problems
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.
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.