Avalanche danger may spike on slopes receiving direct sun. Avoid travelling on or underneath sun-baked terrain.
Confidence
Fair - Timing or intensity of solar radiation is uncertain
Weather Forecast
Friday: Trace amounts of snow. Light N winds. Alpine temperature near -7.Saturday: No snow. Light winds. Alpine temperature near -6.Sunday: Light snow. Light winds. Alpine temperature near -8.
Avalanche Summary
On Wednesday, a widespread natural cycle was observed, with avalanches to size 2.5 failing with solar warming. Cornice fall was also occurring.A size 1.5 skier triggered slab avalanche was reported in the South Chilcotins on Tuesday. This avalanche occurred on a steep north aspect in the alpine and was triggered mid-slope. On Monday, a cornice fall triggered a size 3 slab avalanche on a NE aspect with a crown depth up to 100 cm. There is limited information on an accidentally triggered slab avalanche on Sunday in the Duffey Lake area that resulted in 2 people being buried.
Snowpack Summary
Recent snowfall amounts vary significantly throughout the region. In the Coquihalla area, around 25 cm of recent storm snow has been redistributed by strong winds over a crust, which is supportive to skis to at least 1700 m. A deeper melt-freeze crust was buried around a week ago by up to 90 cm of snow which is settling out. Further to the north (Duffey Lake), lighter amounts of new snow overlie a sun crust, wind slab, or settling storm snow. A buried surface hoar layer can be found down 50-70 cm and may be associated with a sun crust on southerly aspects at treeline. For all areas, expect extensive wind slabs and cornices in the alpine.
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.
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.