Monday's danger ratings are based on the arrival of a heavy storm. Timing of this system is very uncertain. The ratings can be dropped to considerable if it's not snowing or blowing significantly.
Summary
Confidence
Poor - Timing, track, or intensity of incoming weather is uncertain for the entire period
Weather Forecast
Monday: A deep Pacific low spreads moderate to heavy snow to near valley floor (25-30cm). Severe winds and thunderstorms are possible. The timing and intensity of this system are uncertain.Tuesday: Light convective snow. Moderate winds, gusty at times. Freezing level around 600m.Wednesday: The next low pressure system arrives with moderate snow, strong south-westerly winds and freezing level rising slightly.
Avalanche Summary
A few cornice-triggered and small skier-triggered slabs in the size 1-2 range have been reported since it began snowing on Friday. Earlier in the week, warming prompted a widespread natural cycle in the Coquihalla and skiers triggered very touchy persistent slabs at low elevations. An unnervingly large natural avalanche cycle occurred last weekend, with slabs up to size 4.5 propagating 2-3km along ridgelines and stepping down to the mid-February layer. Similar avalanches are possible as storm loading continues this week.
Snowpack Summary
Strong winds and new snow are expected to create new wind slabs and storm slabs which are likely to fail in steep terrain, and could overload persistent weak layers. Persistent weak layers are variable in distribution across the region. A hollow series of poorly-bonded crusts was reported on southerly aspects in the Duffey Lake and Chilcotin regions last week, which may have healed somewhat with dramatic warming at the end of the week. A lower weakness comprising surface hoar, facets and a crust, has produced whumpfs and still is a key concern for step-down avalanches in many parts of the region. It is especially prevalent on south-facing slopes above treeline, and all slopes below treeline.
pgoddard,
Avalanche Canada
