Regions
Vancouver Island.
Avalanche control work at Mt Washington produced a few size ones with explosive control and ski cutting on Saturday. No new avalanches were reported by the resort on Sunday.
Natural loose wet avalanche activity was noted to have taken place late Friday night when rain saturated the new snow that fell during the day up to size 1.5.
A few natural storm avalanches up to size two were also reported from activity sometime during the last three days.
Past Weather
From zero to hero... Our snowpack has gone from thin very spring like conditions to a winter wonderland in a few short days. Multiple storms with strong to extreme SW to SE winds have dumped 40 -50 cm of new snow in the past four days. Unfortunately Friday and Saturdays snow loads were each capped by short lived rain events to well above the 1600 m mark.
Weather Forecast
Another blast of winter will hit from Monday morning until midday bringing more new snow. Atypically the wind will be strong from the NW with this event (reverse wind loading slopes) but the cold air should produce some very nice light dry powder. Things calm down Tuesday and temps remain cold until a warming trend pulls in Wednesday. Monday: An average of 10 cm of new snow will fall in most areas Monday morning-midday, with the exception of around 30 cm near Arrowsmith and only a trace for Mt Cain, temps for 1500 m will range from -2 to -7, winds will be strong to very strong NW, with freezing levels from 400 to 800 m. Tuesday: no new snowfall, temps for 1500 m will range from -1 to -4, winds will be light to moderate from the NW, with freezing levels from sea level to 800 m.Wednesday: no new snowfall, temps for 1500 m will climb from 0 to +4, winds will be light to moderate from the more typical SW, and freezing levels will jump all the way from sea level to 1700 m.
Terrain Advice
-Give wind loaded south east slopes in the alpine and treeline time to settle and bond after the new snow falls in the AM Monday. This snow will likely have a poor bond to the rain crust that formed with the bit of rain Sunday night. -Cornice growth in the Alpine on all aspects will present a danger. Avoid exposure both on top of and below these recent addition to our season.-Warming on Wednesday may make weak layers in the snowpack more sensitive to triggers. Keep an eye on how warm it is getting where you are, and adjust plans as temps get into the positive numbers. -Avoid exposure to steep slopes in forest openings and/or near water sources as a now buried weak layer may linger there.
Snowpack Summary
40 to 50 cm of new snow has fallen recently with short lived rain events after each new addition to the snow pack. Great storm riding was had during the day Friday and Saturday prior to the wet evening warmups. New snow has climbed to a level that surface anchors like trees and rocks are no longer going to prevent avalanches from running. From this point on we need to factor this into our decisions. Typical total snow heights are now around 50 -90 cm below treeline, 90 to 170 cm at treeline and above 200 in the alpine. *A layer of very weak snow crystal has been noted in several snow pits around the Forbidden Plateau area approx 20 cm down on the rain crust that formed after Fridays storm. Tests have produced significant easy (scary) results. Big thanks to our local avalanche course providers for sending in reports.
Snowpack Details
- Surface: A thin rain crust tops the new snow that fell Saturday
- Upper: Another thin rain crust and below that the snow that fell Friday (potential weak layer above this crust)
- Mid: Moist well settled snow and a old crust from the early season.
- Lower: Well settled
Confidence
High - Many days of field data and weather models in agreement
Problems
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.
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.