Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Monday
Weather Forecast
An "almost pineapple" weather pattern is setup across the province directing the firehose at the neighboring regions to the north & west, directing a more modest amount over the Purcells. SUN: FZLVL stays near 1300m. Elevations above the freezing level should see 4 - 8 cm in the afternoon. Ridgetop winds are expected to be Strong out of the West. MON: FRLVL lowers to 900m. 5 -10 cm of snow expected above 900m. Winds 10 - 15cm of snow is expected above 1200m, light rain below. Ridgetop winds remain strong out of the W/SW. Tue: A ridge of high pressure slides into the region bringing more seasonal cool temperatures, high solar & light winds.
Avalanche Summary
No new avalanches to report from the Purcells but, visibility was super limited Saturday by all accounts.
Snowpack Summary
A cohesive slab continues to settle over the mid-February surface hoar, which is generally down in the 40-55cm range. Recent reports include whumpfing and cracking, and moderate but sudden compression test results. This persistent weakness is susceptible to remote triggering and has the ability to propagate in low angled terrain, and the overlying slab structure creates the potential for step-down avalanches. Basal facets have only been reactive on steep, shallow, and rocky slopes, but operators continue to monitor this layer in tests. Triggering this deep persistent weak layer is unlikely, but shallow snowpack areas or shallow weak areas adjacent to deeper wind loaded slopes are the most suspect locations.
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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.