Periods of strong solar radiation may cause a cycle of natural avalanche activity in the new snow. Avalanches in motion or cornice fall may trigger deep slab instabilities.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Saturday
Weather Forecast
Overnight and Saturday: Mostly sunny with light to moderate Northwest winds and freezing level rising to about 1400 metres. The ridge of high pressure is expected to flatten out Saturday evening allowing cloud and light precipitation to move into the region by Sunday morning.Sunday: Expect 10-15 cms of new snow starting in the morning, combined with moderate Southwest winds. Freezing level should be about 1400 metres.Monday: Unsettled weather is forecast for Monday with cloudy skies and light West winds. Models are not in agreement for Monday. Hopefully we will know more tomorrow.
Avalanche Summary
Some small loose dry avalanche were reported from steep terrain on northerly aspects in the alpine. A thin layer of new snow was becoming moist and sliding easily on a recent layer of sun crust on Southerly aspects in the alpine and at treeline. There was one report that was 24 hours old of a remotely triggered avalanche that released down to the February 12th weak layer of buried surface hoar.
Snowpack Summary
There is a thin layer of new snow and wind transported new snow above various sun crusts and old storm slabs, that may release naturally or be easily triggered during periods of strong solar radiation on Southerly aspects. The storm slab continues to settle, and is becoming more stubborn to trigger. The weak layer of surface hoar that was buried on February 12th is now down about 100-150 cms and continues to be triggered by light additional loads on Southerly aspects where it is sitting on an old sun crust. Larger loads like cornice fall or explosives have been able to trigger this layer on various aspects in the alpine and at treeline. If we get a period of strong solar radiation, then we may see another cycle of natural activity on Southerly aspects resulting in large destructive avalanches.
Problems
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.
Storm Slabs
Storm Slab avalanches are the release of a cohesive layer (a slab) of new snow that breaks within new snow or on the old snow surface. Storm-slabs typically last between a few hours and few days (following snowfall). Storm-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.
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.