Regions
Northwest Coastal.
Technical Problems prevented us from updating the forecast today (Saturday). This forecast was first issued on Friday (Nov 23) and is based on information available at that time. We apologize for any inconvenience this may cause.
Confidence
Poor - Due to limited field observations for the entire period
Weather Forecast
Overnight and Saturday: Strong SE winds overnight are expected to ease to moderate with strong gusts during the day Saturday. Alpine temps should lower to about -9.0 and remain cool through Sunday. Expect 5-7 mm overnight and an additional 8-12 mm on Saturday.Sunday: High pressure is moving on to the coast, but it looks like it will remain mostly overcast with some convective snow showers. Winds are expected to switch to the NW and remain moderate with strong gusts.
Avalanche Summary
Some touchy thin wind slabs 5-15 cms have been reported to be releasing in the new snow where it has been transported into a wind slab. Explosives control last weekend produced a couple of 30cm deep size 1.5-2 storm slab avalanches. Natural avalanche activity followed by human-triggered activity generally occurs with every intense weather period, such as what's forecast for Thursday night and Friday.
Snowpack Summary
Total snowpack depth are probably close to a metre in most treeline areas and deeper but more variable in the alpine, while below treeline areas are probably still below threshold depths for avalanches. A recent profile at 1200m in the Shames area showed a predominately "right-side-up" 120cm deep snowpack with a thin layer of facets sitting on a crust 35cm off the ground. An Extended Column Test produced produced easy (10 taps) results on this persistent weak layer , but the resistant fracture didn't propagate across the entire column. Check out the Skeena/Babine discussion forum for more information from the area.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.