Widespread natural avalanche cycles have been playing out in the region. Things should quiet down a step on Wednesday but don't be lulled into complacency as natural avalanches taper off - the potential for human and machine triggering remains very real.
Recent heavy snowfall has perpetuated a natural avalanche cycle involving large storm slabs and wind slabs. The most recent wind slabs--as well as those continuing to form with ongoing wind and light forecast snow--are expected to still be triggereable by riders on Wednesday.
The largest and most reactive slabs will be found on north and east aspects at treeline and above.
A deeply buried weak layer still presents a Low Probability/High Consequence situation. New snow and wind has been testing this weakness in the snowpack and the results still aren't in. This layer would be most likely to be triggered in places where the snowpack is shallow and rocky.
Evidence of a widespread natural avalanche cycle was observed throughout the region on Monday, with storm slabs and wind slabs observed to an impressive size 3 (very large). Many slabs started off dry but finished running as wet loose slides at the bottom of their runouts.
A MIN from Monday at Shames gives some great mid-storm observations.
This activity should serve as an indication of the human triggering potential that could linger through the near term.
Light new snow amounts will continue to add to the 15-40 cm (diminishing with elevation) that constitutes our latest storm snow settling over supportive melt-freeze crust found up to 1800m and on all elevations on steep solar slopes. South to southwesterly winds have been creating wind affected surfaces and wind slabs of varying age and reactivity on an ongoing basis.
This storm snow is only the uppermost fraction of the impressive (and approximate) 100-150 cm of storm snow from the past week that is collectively settling over a layer of facets, crust, and previous wind-affected surfaces in alpine terrain. This interface remains somewhat in question in the wake of the storm.
The mid and lower snowpack continues to bond and stabilize while a number of buried weak layers are still being tracked by professionals in the region, having produced a few large avalanches in the not-too-distant past.
Tuesday night
Cloudy with flurries bringing 5 to 10 cm of new snow, mainly in the far south of the region. Light south winds.
Wednesday
Mostly cloudy with flurries bringing up to 5 cm of new snow, ramping up overnight. Light to moderate southwest winds. Treeline high temperatures around -4.
Thursday
Cloudy with continuing snowfall bringing 30-50 cm of new snow, including overnight amounts. Strong south winds. Treeline high temperatures around -1 with freezing levels rising to 1000 m.
Friday
Becoming sunny as easing flurries leave a final 5 cm of new snow. Storm totals of 40-70 cm. Light to moderate west winds. Treeline high temperatures around -4 and falling over the day.
More details can be found in the Mountain Weather Forecast.
