Regions
Northwest Coastal.
Weather Forecast
Friday: Precipitation will be moderate-heavy with snow amounts 30-50cm, and rain at lower elevations. Freezing levels are expected to rise to 1600m in the southern part of the region (Stewart and south). Ridgetop winds will be blowing strong from the south then switching south west. Saturday: Same story. Moderate - heavy precipitation, rising freezing levels during the day, then falling back to valley bottom at night. Sunday: Looks like a break in the systems. Sunny skies, freezing levels at valley bottom and some vitamin D before Monday's weather rolls in.
Avalanche Summary
Control work with explosives has produced numerous avalanches up to size 3 on east-south facing slopes. On Wednesday widespread natural avalanches up to size 2 were reported. These avalanches all ran on the December 09/12 (111209, 111212) buried surfaces ( surface hoar, melt-freeze crusts). With more wind, snow and rising freezing levels Friday/Saturday we can expect another natural avalanche cycle.
Snowpack Summary
The southern part of the region has received up to 50cm of new snow (Kasiks, Terrace areas) and less snowfall to the north. This is forming storm slabs at all elevations. This new snow is being blown around by strong southwest winds creating new wind slabs on lee slopes. Buried beneath the new snow sits a variety of weak snow surfaces (surface hoar, melt-freeze crusts, and facetted snow). This crust is up to 20cm in thickness and extends up to alpine elevations in the south, and around 1000m in the north. The surface hoar growing on the crust was sized up to 10mm. A strong temperature gradient in the top 30cm was reported to be faceting snow below the surface crust. These layers have met their threshold and widespread avalanche activity has occurred. Here's hopes that this surface hoar will get cleaned out in most places. The crust may stick around and create a new sliding surface for Fridays snowfall. If freezing levels do rise to 1700m on Friday we may see rain and new crust formation Saturday when the temperatures drop back down the the valley.The mid and lower snowpack are well settled and strong.
Problems
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.
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.