Use caution in areas with recent wind deposition
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
Unsettled weather in the wake of the last frontal system that passed through the area yesterday.MONDAY: Cloudy with flurries,10 to 15cm of snow, freezing level around 1200m, and winds moderate from the South.TUESDAY: A break in the weather, cloudy with sunny periods, freezing level may go to 1200m, wind from the South West.WEDNESDAY: Cloudy with flurries, possible 5cm accumulation through the day. Freezing level around 1300m and beginning to climb for the remainder of the week. winds light to moderate from the South.
Avalanche Summary
Explosive control yesterday produced numerous 1 to 1.5 soft slab avalanches. Commercial operators are noting soft slabs in lee terrain. Not many observations reported, mostly as a result of poor visibility during the storm cycle. We expect wind slab activity and cornice failures with the current weather pattern and increased loading, as well as loose-wet avalanches on solar aspects when the sun comes out.
Snowpack Summary
Up to 25cm of recent precipitation on a variety of crusts and old surfaces. Surface hoar and facets may remain in some sheltered locations from the recent clear weather. Moderate to strong south west winds have redistributed the storm snow into wind slabs on the lee sides of ridge tops. A facet/crust layer buried in mid-March has been producing hard and sudden results in snowpack tests. This remains a concern in the region due to it's potential to produce very large avalanches. Cornices are also a concern these days. A cornice failure may trigger a large destructive avalanche. Convective flurries can quickly deposit relatively large amounts of precipitation in a short period with spring weather.
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.