Regions
Kootenay Boundary.
Expect to see the first real warmup of the season with clear skies and rising freezing levels through the weekend into next week. This will initially impact the new snow that fell on Friday, especially on solar aspects.
Confidence
Moderate - Freezing levels are uncertain on Sunday
Weather Forecast
SATURDAY: Mix of sun and cloud / light south wind / Alpine temperature -3 / Freezing level 1400m SUNDAY: Mix of sun and cloud / Light to moderate south wind / Alpine temperature 0 / Freezing level 1800m MONDAY: Mix of sun and cloud / Light south wind / Alpine temperature 3 / Freezing level 2300m
Avalanche Summary
Expect to see an increase in storm slab, wind slab and loose wet and dry avalanche activity as new snow from Thursday night settles and gets kissed by the sun. On Friday reports indicate a few size 2.5 explosive controlled storm snow avalanches running on south aspects at tree line. On Wednesday reports indicated loose wet avalanches size 1.5-2 from southerly facing terrain at tree line. On Tuesday, a size 1 wind slab was skier-triggered on a south aspect at 2200 m and nearby explosive control produced a size 2 wind slab.
Snowpack Summary
15-35cm of new snow has been redistributed by predominantly west and southwest wind and sits on mostly unconsolidated snow from last week and possibly on a sun crust on south-facing slopes.A mix of weak layers exist 50-100 cm below the surface, including small surface hoar on shady aspects and a crust on solar aspects. These layers have consistently been reactive in snowpack tests, suggesting they could potentially remain reactive to human triggers as well. Deeper weak layers that formed in January and December have gained strength and gone dormant at this time. They include several surface hoar and facet layers 1 to 2 m below the surface and a crust/ facet interface near the base of the snowpack.
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.