Periods of strong solar radiation may weaken and release storm slabs on Southerly aspects where a buried crust may act as a good sliding surface. Cornices may also fall off due to solar warming.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Friday
Weather Forecast
Overnight and Friday: Unsettled convective weather is forecast to bring a few more cms of snow overnight and during the day. Amounts may be slightly enhanced in some of the up-slope areas. Alpine temperatures should drop to -14.0 overnight and the freezing level is expected to rise to about 900 metres during the day. Moderate West winds should become light Northerly with moderate gusts. Saturday: A ridge of High pressure is slowly moving into the interior regions from the coast. Cloudy conditions in the morning should clear gradually during the day. There is a chance of a few flurries in the morning. Freezing levels are expected to rise to 1000 metres under clearing skies. Sunday: The ridge of High pressure is expected to continue to bring mostly clear skies and light Northerly winds to the interior ranges. Overnight alpine temperatures are forecast to be about -13.0 with the freezing level rising to 900 metres during the day. Periods of strong solar radiation are expected.
Avalanche Summary
No new reports of avalanches. Poor visibility and travel conditions limited observations.
Snowpack Summary
There is close to a metre of storm snow that has fallen in the last few days. This storm slab is sitting above variable surfaces that include crusts and moist layers that were deposited during the wet (Pineapple Express) storm last week. Periods of strong winds in the alpine transported the storm snow into thick pockets of wind slab that may take several days to settle and bond to the old surface. Cornice growth has been reported to be extensive and weakly bonded. Natural cornice falls are a concern, especially if we see periods of strong solar radiation. Cornice falls or storm slabs in motion may step down to the weak layer of buried surface hoar from March 10th.
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.