Regions
Northwest Coastal.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain on Friday
Weather Forecast
Continued snow and wind through the Holiday weekend. Higher accumulations the further to the North of the region. Friday: Snow amounts 15-20cm. Ridgetop winds 70-105Km/hr from the SW. Treeline temperatures near -5. Saturday: Snow amounts 10-20cms. Ridgetop winds 45-75km/hr. Freezing levels hover around 1200m. Sunday: Snow amounts 10-20cm. Freezing levels 1200m in the morning falling back to valley bottom Sunday night.
Avalanche Summary
Natural avalanche activity up to size 2.5 occurred on Wednesday on a west aspect at 1900m. Heli-bombing control programs also produced slab avalanches up to size 2.5 on all aspects from 1000m and higher. We may see another widespread avalanche cycle through the early part of the weekend. Once it stops snowing and blowing the new snow should start to settle out, and avalanche danger will decrease.
Snowpack Summary
Earlier this week the forecast region got slammed by snow, wind and fluctuating freezing levels. The southern part of the region has received up to 70cms which totals over a meter of new snow over the past week (Kasiks, Terrace areas). Locations to the north are seeing less (Stewart up to 40cms). This new snow has been blown around by extreme-strong southwest winds creating stiff wind slabs on lee slopes. The winds have switched from the SW to the NW. This switch was short lived through Wednesday, but may have formed new wind slabs on SE - S facing slopes. This makes the wind slab problem even trickier to predict. The storms over the past 10 days have created several significant avalanche cycles. My guess is that these repeated cycles have cleaned out most of the mid-December buried surface hoar/facet interface. This is good. The region now sees firm wind pressed surfaces, old bed surfaces (from previous slides), and a crust that extends up to alpine elevations in the south and around 1000m in the north. The next storm will fall on these surfaces, and it's likely that the region will see another large avalanche cycle. The mid and lower snowpack are settled out and strong. Snowpack depths in the Kasiks, Terrace areas are reaching the 300cm mark. Further north Smithers, Bear Pass depths are ranging from 180-250cms.
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.