While humans crave simplicity the current situation is anything but. The answer to the avalanche problem this weekend is staying conservative with terrain selection.
Confidence
Fair - Freezing levels are uncertain on Monday
Weather Forecast
A strong, stable northwesterly flow will prevail over the province while a strong upper ridge remains offshore. The ridge should weaken somewhat on Monday but will still protect the province from Pacific systems.Sunday: Freezing Level: Valley Bottom; Precip: Nil; Wind: Light, Var. Strong NW at ridgetop.Monday: Freezing Level: Valley Bottom with chance of an Above Freezing Layer from 1500 2500m. Precip: Nil; Wind: Light NW, Extreme W at ridgetop.Tuesday: Freezing Level: Valley Bottom; Precip: Trace; Wind: Lht NW, Mod NW at ridgetop.
Avalanche Summary
Avalanches were running naturally and with explosive control to size 3.5 on Friday. The huge avalanches were mostly running on north through east facing slopes at upper elevations and involved the basal weaknesses near the ground. Wind slabs were running naturally on all aspects to size 2. Observations were limited on Friday, I suspect we'll learn more about this most recent avalanche cycle after operators have a chance to get out and see more terrain Saturday.
Snowpack Summary
Thursdays storm brought 25 - 60 cm of snow to the region. This snow lies on top of old wind slabs, a buried rain crust that exists below 1600m and a surface hoar or facet layer that is down 100-150cm deep. The last week has brought around a meter of snow.Snowpack depths vary, but in general 175 cm of snow can be found at treeline, with 125-300 cm in the alpine. In some places we're still dealing with a relatively thin snowpack (thanks to a windy early season). The basal facet/crust combo (weak sugary snow above and below a crust) near the ground was active in Friday's avalanche cycle. This weakness may be difficult to trigger but if triggered, will result in very large, destructive avalanches.
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.
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.