Regions
Vancouver Island.
Observed Size 1 loose dry "sluff" avalanches in extreme terrain. Cracking and small size 1 avalanches triggered by ski cuts in steep unsupported terrain on the storm snow we received during the weekend in leeward terrain.
Past Weather
A Major warm up on Friday and extensive rains were felt up to the Alpine Mountain environment. Late Friday, the air temperature dropped and into Monday we have received a consistent and moderate snowfall amount in excess of 30cm to 45cm depending on aspect, elevation and location on Vancouver Island. The skiing has been great!
Weather Forecast
A large storm cycle of strong precipitation, wind and freezing level fluctuations is expected over the next 24 HRS.Monday - Air temps will rise above zero, (2cm-10cm of snow) in the afternoon precipitation will shift to rain (5mm-20mm Rain) , Moderate mountain top Winds from the SW, Temps O degrees to +2 degrees, Freezing Level rising to 1850MTuesday - Big rise in air temperature will bring about extreme rain up to Alpine (20mm - 80mm Rain), Extreme Winds from the SW will lessen throughout the day but expect more snow transport, unstable snow on multiple aspects at Treeline and Alpine elevation, Temps +3 to -7 degrees, Freezing Level dropping from 2000M to 1,600M later in the day.Wednesday - Forecast models indicate a major drop in air temperatures and light snowfall (1 cm to 5cm Snow), Air temperature steady at -7 with a freezing level at 600M of elevation.
Terrain Advice
Monday is likely the best day to get out explore terrain however later in the day Rain and/or snow is forecast to fall in many parts of the island. As incoming strong rates of precipitation arrive, so too will additional load and stress to the snowpack. Dial back your objectives in terms of slope angle and keep an eye out for snow cracking underfoot, whumpfing and other signs of instability.
Snowpack Summary
Despite the major warm up earlier in the weekend, the air temperatures have dropped back below zero and have helped to consolidate the snowpack. New storm snow has begun to settle. In shallow snowpack regions, a more pronounced surface hoar layer is providing results that indicate less consolidation in the upper snowpack. Monday evening and Tuesday forecasted rainfall may increase load on this problematic layer and contribute to a possible natural avalanche cycle at Alpine and upper elevation Treeline Environments.
Snowpack Details
- Surface: Depending on Aspect and elevation, anywhere from 20cm-40cm of light dry powder snow on a firm rain crust
- Upper: A laminated Rain crust of several ice layers from Friday's major rain event is confirmed from mid island (Mt Wash) to North Island (Mt Cain)
- Mid: A well consolidated mid pack that includes a facet and Surface Hoar Layer approximately 60cm down are increasingly more stubborn to triggers during snow pack testing
- Lower: Well Settled
Confidence
Moderate - Weather models in agreement, Moderate field data available, insufficient Weather station data.
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.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.
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.
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.