Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Wednesday
Weather Forecast
The region moves into a pattern associated with zonal flow. In short, this means that a series of small disturbances will affect the area as freezing levels remain relatively high, around 1200 m or so. It looks like a few cm of snow each day through Tuesday. A more organized system is building in the pacific with some pineapple qualities (warm/ moist) The timing is a bit ruff right now, but it looks to move into the area late Wednesday bringing moderate free precipitation and freezing levels rising to 1500.
Avalanche Summary
Control work in the Dogtooths produced avalanches running to ground on basal facets & depth hoar in high elevation terrain with light loads on Jan. 27th. Further south that day, large loads produced very little results at mid elevations with large loads. Friday's winds formed stubborn wind slabs 20 - 30 cm in depth which were largely unreactive to skiers. Lots of sluffing was reported on Saturday in the region to size 1.5, and that was before the 20 - 40 that fell Saturday night.
Snowpack Summary
The Purcell's are one of the more complex & variable snow packs in the province right now.The Sat/Sun Storm delivered 20 - 40 cm of snow to the region with moderate gusting strong winds out of the SW, S & a bit of SE. This snow fell on a snow pack that is for the most part, pretty well settled.There are a few exceptions though:The Jan. 13th SH/FC combo is still reactive in ski hill testing, but this needs to be taken with a grain of salt as this snowpack is a bit artificial when compared to a true backcountry uncontrolled snowpack. Regardless, I feel like we can't take our eyes of this layer just yet, remember, it's only two weeks old.It sounds like there is a lot of strong snow over the mid December facet layer which is buried approx. 80 cm on the east side and 200+ cm on the west side. This layer seems to have more energy in the Purcells than any other region in the province. On Jan. 28th a skier remoted a size 3 avalanche & this layer was suspected as the weakness.There are basal facets at the ground which are a concern, especially on shady high elevation slopes.
Problems
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.
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.