Be cautious near shallow rocky areas, where a small slab could trigger buried weak layers resulting in large avalanches. Minimize your exposure to overhead hazard, especially on north-facing slopes.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
We've had a bit of a shift from the very cold conditions, and temperatures have warmed by 5 - 10 degrees Celcius. Only some isolated flurries are possible until late Sunday, when a small amount (5-10 cms) of light dry snow is forecast.SATURDAY: Sunny breaks with increasing clouds overnight. Flurries overnight with little accumulation. Winds light southerly. Alpine highs to -13 Celcius.SUNDAY: Mainly cloudy. Winds light southerly. Alpine temperatures between -15 and -20 Celcius; 5-10 cms light dry snow overnight.MONDAY: An additional 5-10 cms light dry snow are possible during the day and overnight. Winds light - moderate southwesterly. Alpine temperatures steady near -14 to -18 Celcius.
Avalanche Summary
A spooky size 3 natural avalanche was spotted in the Liverwurst bowl on a north aspect at 1800m - see today's MIN report at avalanche.ca. The crown is approximately 150cms high and the failure may have been on basal facets, which are large, sugary and weak. A skier triggered size 2 wind slab was reported near Fernie, east aspect also at 1800m.
Snowpack Summary
We're seeing surface snow conditions ranging from very wind affected (sastrugi and hard slabs) to softer wind slabs. The best skiing seems to be on north-facing aspects (but please see the avalanche summary (and MIN report) above and minimize your overhead exposure). These sit on a variety of older wind-affected surfaces at treeline and in the alpine and have given easy test results in the top 15-20cms of the snowpack.That said, the main concern remains the windslabs (and some cornices) formed in the alpine thanks to the recent arctic outbreak winds. Deeper in the snowpack the mid-December persistent layer (facet interface) has been more prominent and reactive in the Corbin zone than closer to Fernie: Watch out for thinner snow packs and areas of crossloading in isolated areas (think shallow rocky areas) where an avalanche could step down to trigger deeper layers.
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.