WIth the forecast storm avalanche hazard will rapidly rise to HIGH on Saturday. A widespread natural avalanche cycle is expected at all elevations.
With a warm wet storm the snowpack will turn upside-down creating a widespread storm slab problem. Strong winds will build windslabs at higher elevations where the snow is dry enough to be blown into deeper slabby pillows.
With freezing level rising to near 2000 m there will be soaking rain at lower elevations. A Wet Loose avalanche cycle is expected.
Friday Overnight: Warm, wet, intense storm ramping up. Freezing level rising to 2000m. Strong southwest wind. Precipitation of 15 to 30 mm water equivalency. Normally that means 20 to 60 cm of snow; with this storm it means soaking rain at lower elevations and up to 30 cm of snow at the highest elevations.
Saturday: Freezing levels lowering with temperatures falling back below freezing by end of day. 5 to 15 mm of water equivalent translates into, depending on your elevation: rain, a mix of rain & snow, or up to 15 cm of snow. Strong west winds.
Sunday: Mix of sun and cloud. Flurries for most of the region but up to 10 cm of snow in western upslope locations. Temperatures have cooled down to around -10 C in the mountains with moderate northwest winds
Monday: Dry. Mix of sun and cloud. Temperatures steady around -1- to -15 C. West to northwest wind at moderate strength.
WIndslabs continue to be reported throughout the region, with this MIN report (with great photo) being a good example of the type of problem we're dealing with. Recent ones were in the size 1 to 1.5 range.
Looking forward, a warm wet storm will create a Loose Wet avalanches at lower elevations and increase the likelihood of Storm Slabs (and Wind Slabs) at higher elevations.
Here's a snowpack description as of Friday Jan 31 before the forecast warm wet "atmospheric river" (previously know as a pineapple express) storm arrives. This description will obviously no longer apply once hit by soaking rain at lower elevations .... The upper snowpack is right-side-up meaning light dry & fluffy (aka powder) at the surface which gradually blends into increasingly harder and stronger snow with depth.The weeks-long weather pattern of snow & wind also means there are widespread storm and wind slabs.
In the mid-pack there's a layer of weaker surface hoar buried in late December that remains a concern but is gaining strength. This layer is found across much of the North Rockies region but our focus is around McBride and the McGregors/Torpy. It's a classic surface hoar layer that's most prominent in sheltered treeline features 50 to 150 cm below the surface.
