35cm of storm snow with strong southerly winds are building storm slabs in the alpine. Winter is here for another 24 hours.
Weather Forecast
Mainly cloudy today with isolated flurries, especially west of Rogers Pass. Freezing level will hover around 2000m with moderate to strong winds from the SW. Tonight will see a general clearing trend with freezing levels staying near 1900m. Tomorrow will see a heat wave roll through, with sunshine and freezing levels rising to 3700m.
Snowpack Summary
The west side of the Pass received up to 20cm last night, bringing the 2 day total to 35cm. East of the Pass received much less. Storm slabs are building with the mod/strong southerly winds in lee areas, more prevalent above 2400m where the snow is cooler. New snow is insulating a warm, moist snowpack, and multiple crusts exist in the upper metre.
Avalanche Summary
Very little activity was noted yesterday. Isolated avalanches to size 2.5 were observed from very steep, N-facing start zones on Mt Macdonald and Ross Peak, travelling as far as the top of the avalanche fan. A field team at the Illecillewaet Glacier toe noted 15-20cm of dry surface snow with over 50cm of weak, moist snow below.
Problems
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
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.