Freezing levels may rise higher than forecast. Where rain falls it will saturate the upper snowpack and cause loose wet and wet slab avalanches.
Confidence
Fair - Freezing levels are uncertain
Weather Forecast
Synopsis: A series of fronts is sliding down the BC coast. The warm front should pass over the Sea to Sky region on Saturday, followed by the cold front Sunday morning. Expect 30 to 60mm of precipitation before conditions dry out briefly on Monday.Tonight and Saturday: Heavy snow / Moderate to strong SW winds / Freezing levels 1500-1700mSunday: Heavy snow / Moderate to strong SW winds / Freezing levels 1500-1700mMonday: Flurries / Light W winds / Freezing levels 1300m.Note: Weather models have been typically under predicting freezing levels thus far through this system.
Avalanche Summary
A cycle of small natural and explosive controlled storm snow avalanche occurred Thursday in response to heavy loading and mild temperatures. Natural activity should taper off a bit on Friday as conditions dry out briefly.Cornices are finally beginning to mature and should be given a wide berth.
Snowpack Summary
Between 30 and 60cm of rapidly settling new snow fell in the recent storm. This was accompanied by strong S-SW winds that formed a thick wind slabs in open lee terrain. The early March melt-freeze crust can now be found down 60-120 cm. This layer was found on all aspects at treeline and below, and on all but North aspects in the alpine. Recent snowpack tests give easy to moderate popping shears on this layer, and show potential for wide propagation.The mid February crust/facet combo appears to be rounding and bonding in areas where it is buried 150 cm or deeper. In shallow snowpack areas, where the weak layer is buried less than 100 cm deep, it continues continue to fail with popping shears in snow profile tests. Big un-supported alpine North aspects are the most likely place to find (and potentially trigger) this well preserved weak layer.Given the current layering in the snowpack be aware of the potential for smaller avalanches to step down and trigger deeper layers and produce very large 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.