Confidence
Fair - Freezing levels are uncertain on Thursday
Weather Forecast
Overnight: Trace of precipitation in the forecast, freezing level drops to valley bottoms overnight. Winds N West gusting mod to strongTuesday: Trace of new snow, winds changing to moderate to strong from the W, freezing levels may rise to 1200m.Wednesday: Light flurries, moderate to strong winds from the west, freezing level to 1000m in parts of the forecast area.Thursday: No Precipitation in the forecast for Thursday
Avalanche Summary
A widespread natural avalanche cycle has taken place in the past 24 to 48 hours as a result of the large amounts of new snow, rising temperatures and high winds. Wind slabs and shallow snowpack areas are places of highest concern now. The possibility of a relatively small to medium size avalanche stepping down to buried weak layers is high, and may produce a very large and destructive avalanche.
Snowpack Summary
More than 75 cm of recent storm snow overlies a variety of old snow surfaces, ranging from stiff wind slabs to soft facetted snow and/or surface hoar that was buried around Jan. 8th. A rain crust below the 1600m elevation band should now be buried over a metre, and another surface hoar or facet layer is down 160 + cm deep. Snowpack depths vary, but in general around 200cm of snow can be found at tree line with 130 to over 300 cm in the alpine. In some places we're still dealing with a relatively thin snowpack (thanks to a windy early season). The basal facet/crust combo, ( weak sugary snow above and below a crust) near the ground was active in an avalanche cycle last week. This weakness may be difficult to trigger but if triggered, could result in very large, destructive avalanches.
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.