Freezing levels will be on the rise through the weekend as a weather system threatens showers for Sunday.
Despite the recent natural avalanche cycle slowing down, expect avalanche hazard to increase through the weekend and keep the deep persistent slab problem at front of mind.
30-40cm of storm snow fell this past week forming widespread slabs in alpine and treeline areas. While these have started to settle out, expect human triggering in steep terrain especially with increasing temperatures, rain, or solar heating.
Freezing levels are on the rise through the weekend and while solar inputs may diminish on Saturday as the weather approaches, the potential for rain at lower elevations on Sunday, when the system arrives, is of equal concern.
The basal facets, as well as mid-pack facets and crusts, remain a significant concern. Many large avalanches in the recent cycle initiated on, or stepped down to, these layers demonstrating the problem is both widespread and possible to trigger.
We have just come out of an avalanche cycle to size 4 which had many full-depth avalanches running full path.
Avalanche control Thursday on Mt. Bosworth produced storm slabs up to size 2.5 and on Mt Bourgeau produced several deep persistent slabs to sz 3.
On Wednesday avalanche control in Kootenay produced slides to size 3.5 with very wide propagations.
Recent storm snow has settled to around 30cm above 2300m. This overlies sun crusts up to ridge top and faceted layers on shady aspects. Below 2300m, shallowly buried crusts lie over a previously isothermal snowpack following recent rain. New sun crusts are forming.
Several buried crusts are in the top 50-70 cm on solar aspects. The bottom of the snowpack remains facetted and weak.
Clearing skies overnight Friday should bring a good freeze. SW winds will build to 30-40 km/h.
Saturday, scattered flurries will begin. Freezing levels will rise to 2000m plus and return to valley bottom overnight.
Sunday, winds increase to strong, 5-10cm of snow (rain?) is likely with freezing levels as high as 2500m.
