Regions
Northwest Coastal.
Watch out for periods of intense weather - convective storms could bring locally heavy snow amounts, which will increase avalanche danger on Thursday.
Confidence
Moderate - Intensity of incoming weather systems is uncertain
Weather Forecast
WEDNESDAY NIGHT: 10-15 cm new snow with strong southwesterly winds.THURSDAY: 5-15 cm new snow that may be quite localized but intense at times. Southwesterly winds 30-50 km/h. Freezing level around 700 m.FRIDAY: Light snow, around 5 cm. Freezing level around 800 m. Moderate southerly winds.SATURDAY: Moderate snow, around 10 cm. Freezing level around 1200 m. Strong southerly winds.
Avalanche Summary
One size 2 wind slab in the north of the region is worth noting: it was remotely triggered from 100 m away suggesting some sort of a persistent slab structure that won't heal overnight.In the south part of the region clouds limited observations but avalanche reports include numerous natural size 2 avalanches on all kinds of terrain 35 degrees or steeper, numerous remotely triggered size 2 slides. I suspect we'll learn more when the visibility improves and people see more terrain.
Snowpack Summary
Moderate amounts of new snow are expected Wednesday night and Thursday, which will add to the 40-60 cm of recent storm snow. This is likely bonding poorly to a wide variety of old snow surfaces: crusts on solar aspects, facets up high and surface hoar in sheltered locations. Not much further below this interface is a second weak layer that was buried on February 19 and comprises weak facets and surface hoar crystals. Recent avalanche activity appears to have been equally split between these two layers.The lower snowpack is generally strong.
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.