If the rain-soaked snow freezes as expected through Friday and Saturday, avalanche hazard will follow a decreasing trend until the next storm on Sunday. Please treat this forecast as an initial assessment, as we have little information at this time.
Confidence
Low - Due to the number of field observations
Weather Forecast
Harmer (1870m):Temps between 2 and 4.5C over last 24 hours. HS decreased from 57 to 43cm. Winds 30-45 SE (prev SW)Crowsnest Ck (1450m):H96W: 18mm; H24W: 12mm; TMax 9; TMin 4S Racehorse Ck(1950m): H96W: 52mm; H24W: 32mm; TMax 7; TMin 3Castle Mtn (1420m): H24W: 14.4mm rain; H48W: 40mm rain. TMin 6; TMax 8; Mod SW winds
Avalanche Summary
There are few observers right now, but avalanches almost certainly ran during the onset of the rain on Wednesday. I suspect this activity will taper off with cooling temperatures on Friday and Saturday.
Snowpack Summary
Rain and warm weather have resulted in a widespread wet upper snowpack. The freezing level rose to approximately 2700 m on Wednesday and Thursday meaning very few places, if any, will have escaped the melt. The last 48 hours have seen the snowpack diminish by approximately 10 cm. Expect treeline snow depths of around 45 cm in the Elk Valley and more like 80 cm further south in the Flathead in sheltered areas. A crust that formed around Halloween has been reported within the snowpack that may lie around 40 cm below the surface.
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.
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.