Regions
Vancouver Island.
Confidence
Moderate - Precipitation amounts on Saturday are uncertain.
Travel & Terrain Advice
Avoid areas with freshly wind loaded snow and cross loaded features. Avoid travelling near or below cornices. Avoid avalanche terrain when rain on snow events occur and temperatures warm rapidly. Choose low angle terrain, simple or non avalanche terrain and be very cautious of even the slightest exposure to overhead hazards
Avalanche Summary
Avalanche control teams at Mount Washington report ski cutting triggering numerous wind-slab avalanches on western aspects and found on all aspects new snow instabilities touchy to skier traffic. These avalanches were size one and easily triggered with light loads and on specific terrain features widespread propagation was noted. Numerous explosives testing produced size 1.5 avalanches on north westerly terrain and had crowns down 20 to 30 cm. One explosive test on a south west aspect produced a large slab avalanche down between 60 and 80 cm and was large, size 2 and it ran far and fast. During the early PM on Thursday temperatures and freezing levels continued to rise with precipitation falling as rain to treeline. Numerous small loose wet avalanches were reported on all aspects and at all elevation from treeline and below. Signs of instability such as pinwheels from steep thin areas where reported as widespread and especially prevalent on steep slopes with rocky out crops and thin areas. Expect these conditions to persist through this forecasting period, as freezing levels will remain high, snowfall that does occur will be moist and heavy and in westerly regions of the forecast area, precipitation amounts may exceed 50 mm in volume.
Snowpack Summary
Moderate to strong south east wind and moderate to heavy snowfall have in areas lee to this wind buried a melt freeze crust down between 40 and 60 cm. This new snow fall has become moist and is bonding poorly to the old surface. Below the well establish melt freeze crust, another crust initially buried March 22 is now down between 100 cm and 130 cm. Numerous Testing of the March 22 crust produced no results, the crust however is well defined and may wake up with a big enough load. The mid and lower snow pack are well settled and dense.
Snowpack Details
Surface: Variable surface conditions, some areas scoured to old crust other in the lee of the wind, up to 60 cm of moist new snow all sitting on a melt freeze crust. Upper: New moist snow. Mid: Widespread March 22 melt freeze crust and in isolated protected north aspects areas its suspected that surface hoar and surface facets may have been buried on this crust. Lower: Well settled.
Past Weather
A period of cold temperatures has been followed by a warm front bringing rising temperatures and freezing levels with moderate to strong south east winds.
Weather Forecast
A low pressure located to the north west of the region, will bring to the forecast area rising freezing levels, warming temperatures, and moderate precipitation amounts. Rainfall is expected to breach the 1800 meter mark Saturday and any snowfall above this elevation will be heavy moist and perhasp wet with potential to trigger large natural avalanches. Friday: 10 mm of rainfall. Temperatures 2 overnight rising to 4.5 mid day, winds light to moderate south east . Freezing level rising to 1700 m mid day. Saturday: 50 mm of rainfall. Temperatures 4 overnight rising to 5 mid day, winds moderate east south east. Freezing level rising to 1900 m mid day. Sunday: 5 mm of rainfall temperatures 3 rising to 6 mid day, winds light to moderate south west. Freezing level rising to 1700 m mid day.
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.
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.
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.