Regions
Northwest Inland.
A storm moving inland from the coast is expected to build new wind slabs by Sunday. There is some uncertainty with the timing. If new snow arrives early these danger ratings may be a bit low for Saturday.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Southerly winds and cloud developing overnight with freezing levels at valley bottoms. Snow starting Saturday morning and continuing during the day. 5-10 cm of new snow expected by Sunday morning with moderate southwest winds and alpine temperatures around -5. Winds increasing to strong during the day with another 3-5 cm of snow and alpine temperatures around -5. Strong winds on Monday with flurries and valley temperatures rising up to near zero.
Avalanche Summary
A couple of size 2.0 wind slab avalanches were reported on Thursday that occurred in the upper Kispiox area that were 40 cm deep and 40 metres wide from steep alpine northwest aspects. In the north of the region on the border of the Northwest Coastal region we had a report of remotely triggered avalanches up to size 1.5 in the alpine and at treeline.
Snowpack Summary
The region has a mix of wind slabs and developing storm slabs. In higher snowpack areas in the northwest of the region, the storm slab has become reactive to human triggers. In most areas the wind slabs are thin and stiff, however we have had some reports of surprisingly deep wind slabs earlier this week. Buried surface hoar is layered through the thin snowpack, and cool temperatures as well as limited loading have preserved these weak layers. The mid pack that was reported to be well settled may have now facetted in the shallower areas, and the deeper basal layers are almost certainly facetted and weak. We have not heard of any full depth releases on weak basal layers yet.
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.