Regions
Banff Yoho Kootenay.
Expect a poor freeze below 2300m Saturday and increased PM danger if the sun pops out. We will be switching to "spring conditions" over the next couple of days. The coming week looks to be a warm one.
Weather Forecast
10cm along the divide and only a few cm (maybe some light rain) along the eastern slopes expected Saturday. A poor lower elevation freeze can be expected, temps will start to cool as a cold front moves through mid day. Upper elevation SW winds will increase through the day. Next week looks like a dramatic warming trend.
Snowpack Summary
Up to 50 cm of storm snow near the divide affected by strong SW winds Tuesday evening. Several buried temperature crusts exist to 2000m on all aspects and to ridge tops on solar slopes, including the Mar 15 sun crust down 35-50 cm in the alpine. Moist snow at lower elevations, with the entire snowpack becoming moist near valley bottom.
Avalanche Summary
Avalanche control yesterday produced mainly windlslabs in the sz 2 range 20-50cm deep with decent propagations up to 50m wide. Several of these events entrained more mass as they moist snow at lower elevations. During flights, evidence of a natural cycle to sz 3 could be seen in the Banff region mainly Ne facing windslabs from the last 48 hours.
Confidence
Freezing levels are uncertain on Saturday
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
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.