Danger on SOUTH and WEST facing slopes could be CONSIDERABLE in the afternoon.
Confidence
Fair - Due to limited field observations
Weather Forecast
Tuesday: Mostly clear skies, with a chance of clouds developing late in the day. Further inland (Coquihalla, Alison Pass) may see more cloud. Alpine temperatures should climb to -6 with freezing levels reaching 1400m. Winds should remain light from the northeast.Wednesday: Expect clouds to build through the day with alpine temperatures reaching -6 and winds turning southwesterly and increase to moderate values. Freezing levels could reach 1500m with possible isolated flurries late in the day.Thursday: Mixed skies are likely with temperatures reaching -2 and freezing levels climbing to 1600m. Expect light westerly winds and a chance of isolated flurries.
Avalanche Summary
Numerous rider triggered and isolated remote/sympathetic events have been reported in high (2400-2700m) north and northeast facing slopes up to size 2.0, all associated with preserved surface hoar.
Snowpack Summary
Recent convective snowshowers (Thursday to Sunday) have given up to 45cm of new snow at higher elevations. The surface snow is going moist on all aspects up to 2000m and continues moist into the alpine on solar aspects due to strong solar inputs. The new snow interface is predominantly crusts (sun, wind, meltfreeze) and the bonds are slowly tightening.The previous storm (Wednesday) was accompanied by moderate to strong south/southwest winds which left variable snow distribution in exposed areas near ridgetop with dense wind slabs in lee and cross-loaded features. These slabs are now buried, but may still be reactive to heavy triggers or in specific locations. Up to 75cm below the surface you will likely find a melt-freeze crust from previous sunny weather. At the same interface, spotty surface hoar is still being reported (up to 20mm!) in some high, north facing slopes. Where the surface hoar is present, consistent sudden results have been observed.Cornices are huge and have grown new tabs under the current conditions.
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.
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.
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.