Northwest Coastal

The storm may have tapered-off, but persistent weaknesses have to the potential to surprise with nasty consequences. Conservative terrain selection remains critical.

Fair - Timing of incoming weather systems is uncertain on Wednesday

Generally light snowfall, strong southwest winds and freezing levels at 600m are expected on Wednesday. Snowfall is expected to intensify Wednesday evening and continue throughout Thursday. By Friday morning, we can expect up to 25cm of accumulated snowfall. Winds are forecast to remain strong and southwesterly during the system, and then become light and northwesterly as the snowfall tapers-off on Friday. Freezing levels should hover around 800m for Thursday and Friday.

In recent days, a widespread natural avalanche cycle took place to size 3.5. These avalanches were triggered by loading from heavy precipitation, wind, and warm temperatures. Many avalanches failed within the recent storm snow, although numerous avalanches also failed on persistent and deep persistent layers. At lower elevations where precipitation fell as rain, loose wet avalanches to size 2 were also observed. With forecast snow and wind, I expect ongoing storm slab activity with the potential for deeper destructive persistent slab avalanches.

Moderate to heavy snowfall (with rain at lower elevations) and strong southwest winds have built deep and dense storm slabs. These storm slabs are expected to be most reactive in wind-exposed, upper elevation terrain. A rain crust and/or surface hoar layer buried mid-January can be found about 100cm below the surface. This persistent weakness has been reactive with recent storm loading, and was responsible for much of the recent large avalanche activity. The November crust near the bottom of the snowpack is generally well bonded. That said, this deep and destructive layer "woke-up" in response to heavy snowfall, wind and warming over the last few days producing very large avalanches in isolated terrain.