Confidence
Fair - Freezing levels are uncertain for the entire period
Weather Forecast
Wednesday the region may have seen the last drips and drabs of precipitation for a while. A strong ridge building from the western part of the province will bring dryer conditions for the forecast period. On Thursday ridgetop winds will be light from the NW; freezing levels may rise to 1200m and alpine temperatures steady near -5. Friday and Saturday the ridge of high pressure holds true with freezing levels potentially reaching 1800m.
Avalanche Summary
On Tuesday two size 2 slab avalanches were reported in the Dogtooth range on Repeater Ridge. These occurred on a East aspect @2400m. On Monday explosive avalanche control done in the Dogtooth Range produced 2 avalanches up to size 2, running full depth to ground basal facets. These were on NW-N aspects, @ 2300m.
Snowpack Summary
The Purcell region hosts a complex and variable snowpack right now.Up to 40cms of storm snow fell over the weekend. This new snow was accompanied by moderate to strong winds from the SE-SW. Wind slabs are likely to be found on exposed areas at treeline, and above into the alpine. Storm slabs can be found at all elevations. Reports indicate these slabs are touchy; especially to rider triggers. This new snow fell on a snow pack that is for the most part, pretty well settled. Yet, there are a few exceptions. The Jan. 13th SH/FC combo has been reactive in ski hill testing. Remember this is somewhat of a modified snwpack when compared to a true backcountry uncontrolled snowpack. Regardless, I feel like we can't take our eyes off 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 and was reactive on Jan. 28th, when a skier remotely triggered a size 3 avalanche. At this point we're looking at a low probability high consequence situation.There are basal facets at the ground which remain a concern, especially on Northerly aspects at high elevations. During the earlier part of the week a couple of slab avalanches have occurred, running down to these basal weaknesses. Snowpack depths at 2000m sit near 2m deep.
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.