Sunny skies and solar radiation will exist through the forecast period. Southerly slopes may deteriorate, natural avalanche activity could spike.
Confidence
Fair - Freezing levels are uncertain on Thursday
Weather Forecast
A ridge of high pressure off the South Coast will continue to bring dry, warming conditions until Friday. As the ridge tracks inland it starts to break down, allowing a southwesterly flow to begin. This will bring unsettled conditions into the weekend. Wednesday: Some cloud in the am, high cloud in the afternoon, sunshine. Ridgetop winds moderate from the NW. Treeline temperatures near -6. Freezing levels 900m. Thursday: Clear, sunny and dry. Ridgetop winds moderate from the West. Treeline temperatures near -2. Freezing levels rising 12-1500 m, falling to 700 m overnight. Friday: Sunny skies. Ridgetop winds strong from the SW. Treeline temperatures near -2. Freezing levels 15-2000 m. Flurries expected overnight.
Avalanche Summary
On Monday the region saw a widespread natural avalanche cycle in response to snow, wind and warming. Operators are reporting numerous size 1-3.5 natural avalanches, starting in the alpine on all aspects, and running full path. Rider triggered slabs were also reported in the size 1-2 range, failing on storm snow weaknesses. There are still reports of remotely triggered avalanches up to size 2.5 on suspected mid-February SH interface.
Snowpack Summary
Over the weekend, up to 80 cm of storm snow fell. Strong winds from the SW and fluctuating temperatures were the perfect recipe for storm slab, and wind slab instabilities. This new snow has buried variable old surfaces (surface hoar, facets, and crusts) that formed mid-February. These persistent weak layers have remained touchy all week and are a key concern at all elevations. If triggered, the avalanches will be larger than expected. Sunny, clear skies are likely to exist through the forecast period. Moist-wet snow surfaces, snowballing, and point release (loose wet slides started from a point, gathering mass in a fan-like shape) are indicators of a deteriorating upper snowpack. I'd be weary of south facing slopes, affected by solar radiation. There may even be step-down potential on deeply buried weak layers. Large cornices have formed and loom as potential triggers on the slopes below.
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.
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.