Regions
Vancouver Island.
Confidence
High- significant snowpack observations and weather forecast models in agreement.
Travel/Terrain Advice
The desire to play in the powder Friday will be strong, with the knowledge that rain and warm temps are on the way this weekend. Be very cautious, use conservative decision making and careful snowpack evaluations when traveling up or down into north-west facing wind loaded zones. If entering steep avalanche terrain and loaded bowls, proper avalanche gear, knowledge and education is a must. Take extra care and use safe techniques like skiing one at a time, safe zone to safe zone. This weekend travel in avalanche terrain is not recommended! Significant weak layers exist in the snowpack that have shown failures in snow studies. These layers will wake up and become very active once the rain begins to fall to the very top of our mountains. Wet rain soaked avalanches are extremely powerful and present extreme danger when combined with terrain traps. Avoid exposure above cliffs, depressions, tree bands and steer clear of gully features. Remember wet avalanches tend to travel further than we expect and can run well into lower elevation bands and valleys. Also a friendly reminder that skiing is not permitted in closed terrain on Mount Washington. It is very likely that active avalanche control work will be underway over then next few days. Please for your safety and that of the avalanche teams, stay out until gates are opened and do not cut under rope lines.
Past Weather
Strong to moderate winds from the south-east accompanied the new snowfall (up to 15cm) Thursday. Freezing levels have stayed low (below 1000m) in the east but did jump up to 1300-1400 m in the west and north.
Avalanche Summary
Thursday saw a marked rise in avalanche activity/sensitivity by both natural and human triggering. Wind slabs up to size 1.5 were very easily triggered while skiing treeline and below treeline N-E aspect terrain on steeper pitches and unsupported convex features. The majority of these slabs ran down 5-25 cm on the January crust. Natural activity was also seen on steep north facing treeline terrain. Visibility has limited any alpine observations.
Snowpack Description
Surface - New low density snow in wind sheltered zones. Exposed areas have wind pressed slab properties but still ski well. Upper - New snow everywhere with a thin non-supportive crust, approximately 15-30 cm down on below treeline and treeline terrain from Monday's warm spike. Strong to moderate south east winds have added to wind slabs on the north to west aspects in the alpine and treeline. All this new load (in some areas up to 60 cm) is sitting on the January 6th rain crust which has shown significant weakness and failures in tests (producing moderate non planar results) Mid - The new snow and crust buried on Jan 6th is now bridging and almost eliminating concerns surrounding the mid Dec and mid Nov crusts. The moist mid snowpack seams very stable producing only hard results in tests on the Dec crust.Lower - Well settled.
Weather Forecast
Moderate to strong south east winds through the forecast period. More new snow for Friday with rain to the top of our mountains for Saturday, easing Sunday. Very high freezing levels and temps into the weekend.Fri - 5-20 cm of new snow. Winds moderate to strong south east. Freezing levels of 600-1200 mSat - 10-20 mm of rain. Winds moderate to strong south east. Freezing levels of 1200-3000 mSun - 0-2 mm of rain. Winds moderate to strong south east. Freezing levels of 2300-3000 m
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 Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.