Regions
Vancouver Island.
We are releasing a SPECIAL PUBLIC AVALANCHE WARNING for Vancouver Island in conjunction with Avalanche Canada.
We received multiple reports of human triggered avalanches (Size 2+) from mid island to North island including two separate incidents with full burials and serious injuries. These two separate and serious avalanche incidents occurred at the Below Treeline and Treeline Elevation Bands. The likelihood of people triggering an avalanche on a slope steeper than 30 degrees is "very likely" and/or "certain" at this time. Please ski and snowmobile safely, select low angle terrain (terrain under 30 degrees) until the new snow load consolidates and general snowpack stability improves.
Avalanche Forecaster confidence is HIGH : Based on extensive data collection all week as well as many people submitting observations from the field.
Past Weather
Cold temperatures (below zero degrees) and strong to moderate precipitation have left the mountain environment on Vancouver Island with 40cm to 70+cm of new snow. Warmer air temperatures Monday Feb 1st have brought additional snow and possibly rain to the Below Treeline elevation band.
Weather Forecast
The weather pattern for Vancouver island will be quite dynamic for the next several days. Unfortunately, incoming weather is such that the current snowpack instabilities will not see an improvement to stability in the short term.Tuesday (10 cm Snow to 25 cm Snow), Moderate Southerly winds gusting to strong Southerly winds in the afternoon, Freezing level 850MWednesday: (5 cm Snow to 10cm Snow ), Moderate winds from the North, Freezing level 950MThursday (Less than 10cm Snow for North Island) and (5mm Rain for Below Treeline and Treeline Elevation band for South and mid-island), Extreme winds from the Southwest, Freezing level begins at 700M elevation in morning and rises to 1700M elevation late afternoon.
Terrain Advice
Keep to simple terrain (terrain under 30 degrees slope angle) and utilize small slopes to test the reactivity of the recent snowfall.Keep an eye on snowfall rates, wind transport and rising temperatures for your area, as this promotes slab formation and “touchy/easily triggered” conditions.Be cautious when route-finding and transitioning from scoured areas into areas of wind loaded snow.Avoid open and steep slopes during periods of warming and rain. A small loose wet avalanche will entrain and gain enough mass to push a mountain traveller into gullies and over cliffs.Tree well hazards will pose a major hazard this weekend if the forecasted precipitation/winds arrive as predicted. Keep an eye on your riding group and ride in pairs.Avoid travelling above or below cornices and keep to conservative decision-making.
Snowpack Summary
Over the weekend, 40 cm to 70cm of snow fell and was transported by southeast winds creating slabs in the current affected areas. This overlies a sandwich of reactive melt-freeze crusts and persistent weak layers (PWL's) within the upper 60-80 cm of the upper snowpack. Below this, the snowpack is well settled.
Snowpack Details
- Surface: 40cm to 70cm of new snow
- Upper: Two persistent weak layers (contributing to dangerous avalanche conditions on Vancouver Island)
- Mid: Well settled and dense.
- Lower: Well settled and dense.
Problems
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
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.
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.