Regions
Vancouver Island.
No new avalanche activity from Mt Washington patrol
Reports of ski accidental and natural triggered avalanche activity, possibly up to size 2 from Mt Cain's west bowl. All second hand info at this time. Hopefully the parties that experienced these can send us some more info.
Widespread pinwheeling (ie very small loose wet avalanches) have been reported at below treeline elevations island wide.
Past Weather
Little snow has fallen over the weekend. (Mt Cain got the most with 14 cm, Strathcona Park 7 cm, Mt Washington 2 cm, and the southern reaches at around 10 cm. Strong winds have continued to move this snow around to create variable depths depending on your location. Temps climbed as the freezing levels went up to approx 1300-1500 m on Sunday and then cooled as the evening chill set in. Some light rain was reported at lower elevations Sunday.
Weather Forecast
Moderate amounts of new snow are forecast to fall with most expected Monday and Wednesday. Strong winds from SE to SW will move the new snow around. Temps will drop after the warmth of Sunday, cooling the upper snowpack. Monday: 10 to 20 cm of new snow. Winds strong south to moderate west and south west. Temps -1 dropping to -6. freezing levels 1300 dropping to 600 m. Tuesday: 3 to 9 cm of new snow. Winds moderate south to south west. Temps -8 to -4. Freezing levels 200 to 800 m. Wednesday: 25 to 2 cm. Winds strong south east to moderate south east. Temps -5 to -1. Freezing levels 400 to 900 m.
Terrain Advice
Continue to avoid wind loaded terrain in the alpine and treeline. Moderate amounts of new snow and strong winds, during this forecast period, will only add to the windslabs that developed previously.Moderate amounts of new snowfall Monday and Wednesday will load on a hard sliding surface (old crust) in previously wind stripped zones. Take the time to dig down and check what the new snow is lying on and how well it is or is not bonding to the layer below. Give cornices a wide berth as winds of late will certainly have expanded their size. Avoid travel above and below these ridge top features..
Snowpack Summary
The alpine and open spaces at treeline have been beaten by the winds over the past few days. Moist snow (due to warm temps and some light rain Sunday) at treeline and below treeline elevations are now cooling to a thin crust.
Snowpack Details
- Surface: Wind blown snow up high. Moist snow now freezing to a new exposed crust at lower elevations
- Upper: An old crust with a moderate bond to the snow above it. Some preserved dry snow under the crust.
- Mid: Well settled with a dormant persistent weak layer and old crusts
- Lower: Well settled
Confidence
Moderate - Few reports from the field/public. If more reports come in we will try and update the bulletin. Weather models in agreement. Warm/moist trend ending and cold temps on the way to tighten the upper snowpack.
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.
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.