Northwest Coastal

Fair - Intensity of incoming weather is uncertain on Thursday

Wednesday: Mainly dry as an upper ridge builds. Ridgetop winds will be in the 70km/hr range, lowering to 50km/hr as the next system approaches. Snow amounts 5-10cm in the evening. Treeline temperatures near -7. Thursday: Strong southwest winds. 25-30cms of snow with freezing levels rising to 1000m then falling to valley bottom. Friday: 10-20cms of snow. Strong southerly ridgetop winds. Freezing levels rising to 1000m.

A widespread natural avalanche cycle hit the region on Monday. Large avalanches up to size 3 occurred on all aspects at all elevations.Operators are still suggesting that this weak buried interface has been very touchy, reactive and the results being large avalanches. This problem may be on its way out with continued storm loading and stress. At this point we need to remain conscious of this interface, and the re-loading of previous bed surfaces as the next storm hits the coast on Thursday. We may see another widespread avalanche cycle Thursday and Friday. Once it stops snowing and blowing the new snow should start to settle out, and avalanche danger will decrease.

The forecast region continues to get 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) but still enough to create avalanche problems. Storm slabs are thickening at all elevations. This new snow has been blown around by strong southwest winds creating wind slabs on lee slopes. The winds are forecast to switch from the SW to the NW, this change is short lived (24hrs) but will form new wind slabs on SE - S facing slopes. This makes the wind slab problem even trickier to predict. Beneath the new storm snow (anywhere within the upper meter of the snowpack) sits significantly weak layers including a melt-freeze crust with surface hoar above the crust and facetted snow below the crust. This interface is a result of rain and then the early December dry spell. 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. I suspect the surface hoar has been cleaned out in most locations during the past storm cycles. I'm sure it still exists in some locations; especially where snowfall amounts have been less. With more forecast snow and wind these layers should reach their threshold. If they have, you can expect re-loading to occur on the bed surfaces. The extent of the avalanche problems exist in the upper meter of the snowpack. The mid and lower snowpack continue to be well settled 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.