Confidence
Fair - Wind speed or direction are uncertain on Sunday
Weather Forecast
Overnight and Sunday: NW winds 10-20 km/hr overnight with 0-2 mm precipitation by morning. During the day, the temperature in the Alpine is expected to reach near zero as an inversion is expected to develop near the coast and then push into the interior. Winds are expected to gust to extreme values Sunday evening.Monday: The ridge of High pressure is forecast to bring mostly sunny skies through the day with light winds and alpine temperatures slightly below zero. Winds are expected to increase in the evening.Tuesday: A gusty cold front is forecast for Tuesday. Expect moderate Westerly winds to shift to the South and bring 15-20 mm of precipitation.
Avalanche Summary
Some natural cornice falls were reported up to size 2.0 after the recent very strong wind event. Some explosive controlled stiff wind slabs were reported up to size 1.5 from the Whistler area.
Snowpack Summary
The recent very strong wind event has caused extensive wind scouring in the alpine and at treeline. Ski penetration is limited to about 15-20 cm above a stiff buried wind slab. Foot penetration may still be up to 70 cms as the wind slab is not able to carry the weight of a person without skis. The recent storm snow (up to about 130 cms) appears to be bridging above the early November weak layer, and we are not seeing deep releases down to the rain/ice crust. There is not much discussion about surface hoar that was buried last week, and we are not getting reports about test results on that layer. Professionals are concerned about the early November rain crust. If this deep persistent weak layer (DPWL) becomes reactive, the consequences will be very large destructive avalanches. The crust may be buried between 100-200 cms depending on the total depth of the snowpack in your area. The crust may be a bigger problem where it has a layer of facetted crystals above, rather than where it is like a laminated sandwich of crusts and facets. If that sounds too technical for you, then the take home is that this is not an easy problem to gauge when or where it might wake up.
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.