Warm, windy and wet weather is expected to result in natural avalanche activity and increased avalanche danger.
Confidence
Fair - Due to the number of field observations
Weather Forecast
On Tuesday freezing levels are expected to rise as high as 2500 m as a Pacific frontal system brings up to 60-80 mm of precipitation and extreme southwesterly alpine winds. Wednesday is looking slighly drier and cooler, but freezing levels still above 2000 m and 40-50 mm of precipitation. Thursday is looking slightly drier and cooler again with freezing levels dropping below 2000 m and another 10-20 mm of precipitation as alpine winds shift to moderate southeasterlies.
Avalanche Summary
There have been no recent reports of avalanches in the past several days; however, I suspect it may be possible to trigger new wind slabs in open leeward terrain, particularly in the alpine.
Snowpack Summary
Recent snowfall amounts vary but in some areas above 1800 m there could be 20-40 cm of moist storm snow, which has refrozen with another crust on the surface. This buried the previous snow surface of surface hoar or facetted snow in sheltered areas, which probably no longer sensitive to triggers. The midpack consists of more crusts and old facets. The snow pack depth drops significantly below treeline with essentially no snow below 1600 m.
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.
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.