Regions
Banff Yoho Kootenay.
Clear sky's and warming temperatures this week will likely effect the upper snowpack. Watch for an increase in loose dry avalanche activity on solar aspects with daytime warming.
Weather Forecast
Hope on the horizon with warming temperatures approaching for the week. Evening temps for the start of the week will continue to be frigid with lows dipping in the mid -20's, but clear sky's and daytime highs around -5 will be a welcome change. With warming temps we can expect solar triggering to become more of a concern southerly aspects.
Snowpack Summary
Prolonged cold temperatures have weakened the upper snowpack. Wind effect is common in the alpine and several recent crusts can be found on steep solar slopes. Despite the weakening slab above it, Jan 17 surface hoar lingers down 40-60 cm in isolated locations and produces hard, resistent shears. A weak basal snowpack exists in thin snowpack areas.
Avalanche Summary
On a flight over the forecast region today we observed a few large triggers (cornice and seracs) impacting slopes below, causing only small avalanches given the size of trigger. The loose dry problem remains the main concern. We continue to see natural and human triggered avalanches out of most steep terrain.
Confidence
Timing or intensity of solar radiation is uncertain
Problems
Loose Dry
Loose Dry avalanches are the release of dry unconsolidated snow and typically occur within layers of soft snow near the surface of the snowpack. These avalanches start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-dry avalanches include point-release avalanches or sluffs.
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.