Be cautious near shallow rocky areas, where a small slab could trigger buried weak layers resulting in large avalanches.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
We're beginning to see a shift from the very cold conditions of late with daytime temperatures warming up by 5-10 degrees Celcius. Only some isolated flurries possible until late Sunday when a small amount of snow may fall (5-10 cms).FRIDAY: Mainly cloudy. Wind becoming southwesterly 15-25 Km/h. High temperatures near -14 and lows to -28 Celcius overnight. Small chance of isolated flurries. SATURDAY: Sunny breaks with increasing clouds late in the day. Slight chance of flurries. Winds light southerly. High temperatures near -12 and lows to -22 Celcius.SUNDAY: Increasing clouds. Wind light and variable. Temperatures between -15 and -24 Celcius; 5-10 cms light dry snow possible overnight.
Avalanche Summary
No new avalanche observations.
Snowpack Summary
We're seeing surface snow conditions ranging from very wind affected (sastrugi and hard slabs) to softer wind slabs. 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.