Spring conditions: cold nights, warm days, crusts and cornices. High elevations and north aspects will likely remain cool, but conditions will change rapidly at lower elevations and throughout the day.
Weather Forecast
A ridge of high pressure remains over the area today, bringing mainly sunny skies, freezing levels to 1500m, light winds, and potentially intense solar radiation. A disturbance will move through tonight. Wednesday will see a mix of sun and cloud.
Snowpack Summary
Solar aspects have a series of buried sun crusts, some of which have surface hoar on top, creating potential for wide avalanche propagation with the right trigger. These aspects also tend to be windward (SW) so the snowpack is thinner there, and may be more easily triggered by skiers. Strong daytime warming will weaken the snow.
Avalanche Summary
A few very large avalanches were observed in the Selkirks yesterday. Most of these were triggered by cornice failures. One size 3 was observed from MacDonald into the highway corridor - quite impressive. Skiers triggered an avalanche two days ago on a west aspect, in a thin snowpack area. It failed on a suncrust with surface hoar on top.
Confidence
Timing or intensity of solar radiation is uncertain
Problems
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.
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.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.