Regions
Northwest Coastal.
Confidence
Fair - Forecast snowfall amounts are uncertain on Thursday
Weather Forecast
The ridge of high pressure is expected to bring clear skies and colder temperatures to the region on Wednesday. The temperature in the alpine should be about -15.0 and the winds should increase to about 40 km/hr from the west-northwest. Cloud and light precipitation should move into the region from the Pacific during Wednesday evening, and should become moderate to heavy by late Thursday morning. This system is expected to bring 15-20 cm of snow to higher elevations near Terrace, 30 cm to the mountains near Stewart, and 5-10 cm to the Smithers area. The storm should have passed by Friday mid-morning when arctic air is expected to start to move into the region.
Avalanche Summary
A couple of loose snow avalanches up to size 2.0 from very steep terrain at higher elevations have been reported. There was one very large avalanche triggered by a large explosive charge above the highway and rail corridor; the avalanche released down to the ground.
Snowpack Summary
Some areas are reporting an alpine snowpack of 5 metres. In these areas the mid-december surface hoar is buried down about 250 cm with a well settled and strong 80 cm above. These deeper snowpack areas are reporting that there are no shears except in the top 50 cm of storm snow; and these shears on recent stellar crystal weakness are expected to bond within the next few days. Areas that experienced very strong winds during the recent storm may have thick windslabs that may take another couple of days to settle. The lower snowpack is generally well settled and strong.
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.