High freezing levels, moist snow, and strong winds will result in High Avalanche Danger at all elevations.
Confidence
Fair - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
Overnight and Thursday: The next strong pulse of moisture is forecast for Wednesday night, and is expected to continue during the day on Thursday. 10-20 cms overnight and another 20-30 cms during the day. Warm temperatures are not expected to lower overnight, and freezing levels should remain at about 1600 metres.Friday: The Pacific moisture feed should end by late morning as the Low pressure system tracks Northward up the coast. Temperatures and freezing levels should begin to lower. Chance of some broken skies in the afternoon.Saturday: Continued unsettled weather in the wake of the storm. Poor confidence in weather scenarios for Saturday.
Avalanche Summary
A widespread cycle of natural avalanches up to size 2.0 was reported early in the storm before poor visibility and travel conditions limited observations.
Snowpack Summary
Another pulse of heavy precipitation is forecast to add to the already moist heavy storm slab that is covering a widespread layer of surface hoar (March 10th layer) that developed during the recent clear weather. Strong Westerly winds during the storm have developed thick wind slabs at higher elevations where the snow was drier and easily transported. Sun crusts also developed during the clear weather on solar aspects up to about 1800 metres. Some areas had strong winds before the surface hoar was buried, so the distribution may be specific to sheltered and shaded terrain features. There is still concern for the buried weak layer of surface hoar from February 12th that is now down more than a metre in most places. The forecast new load of snow and wind may overload this deeply buried weak layer in areas that did not slide after the last storm.
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.