Regions
Northwest Coastal.
Weather Forecast
Arctic Air continues to sweep down from the North influencing the NW Coast. Under this pattern the region will see cold temperatures: At 1500 m on Monday you can expect a High of -20, Low of -31. Ridgetop winds will be from the E, NE at moderate values under mostly sunny skies. This pattern looks to persist through Thursday.
Avalanche Summary
Sluff & loose snow avalanches to size 1 have been reported. There are also limited reports of snow "cracking" which is indicative of wind slab formation.
Snowpack Summary
20 - 30 cm of new snow has fallen across the region since last Thursday. In wind exposed locations this new snow fell on old stubborn wind slabs. Reports from the region indicate that the new snow is bonding well to the old snow surface. Snowpack depths vary from 3.5 to 5 m across the region. In this part of the province, the mid-December surface hoar/facet combo layer is inactive as it's now 2.5 m below the snow surface. For the most part, avalanche concerns are limited to storm snow instabilities.By Monday the region should be firmly in the grasp of an outbreak of Arctic Air and while I suspect this cool dry air will help to tighten up the snowpack it will also introduce reverse wind loading which could lead to windslab development in unusual 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.
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.