Regions
Northwest Coastal.
Strong winds could turbocharge new snowfall amounts on Tuesday: Dial back your terrain choices if you see more than 25cm new snow. Be extra vigilant if the fresh snow is falling on a smooth sliding layer, like firm sun crusts or hard wind slabs.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Tuesday
Weather Forecast
Snowin' and blowin' on Tuesday followed by a cold front and a more organized system on Thursday. TUESDAY: Snow (5-15 cm, with locally higher amounts) / Moderate to strong south - west winds / Alpine temperature near -1 C / Freezing level 700 m.WEDNESDAY: Cloudy with flurries in the afternoon (5 cm possible) / Light south east winds / Alpine temperature -2 C / Freezing level 600 m.THURSDAY: Snow (10-20cm) / Moderate to strong south east winds / Alpine temperature near 0 degrees C / Freezing level 500 m.
Avalanche Summary
Over the weekend, several wet loose avalanches to size 3 were observed at tree line and below, primarily on sunny aspects. Some of these stepped down to basal facets in northern parts of the region.On Monday we received reports of a skier triggered size 1 wind slab on a north-east aspect near 1600m elevation. The slab averaged 20cm thickness and ran on the March 9th surface hoar / facet layer. On Sunday we received reports of a glide avalanche near Terrace, size 3 on an east aspect near 700m elevation. On Saturday, explosives control work near Stewart produced several wet loose and wet slab avalanches to size 3. Some avalanches stepped down to the mid December ice layer. On Friday, a remote-triggered size 2 persistent slab was reported near Stewart, running on an east facing rib feature near 1600m. The slab (30-120cm thick) failed on the mid January layer, with surface hoar 4-8mm reported.
Snowpack Summary
Recent warming has melted and refrozen the snow surface on sunny aspects. The new snow on Tuesday could be falling on wet snow down low, a melt-freeze crust on south-west aspects, wind slabs higher up, or even preserved powder on north facing slopes above 1100-1300m. Last week, strong easterly to southerly winds redistributed any available soft snow and produced variable surfaces at high elevations, including wind slabs in lee and cross-loaded features. On March 9th, 5 to 20 mm surface hoar or smaller facets (on sheltered, shady aspects) were buried by the last significant snowfall. This layer is still active in some areas (see Avalanche Summary above).Beneath this, layers of crusts, facets, and isolated surface hoar buried 50 to 100 cm exist below the surface from mid- and late-February. A surface hoar and crust layer from January is buried around 150 to 200 cm.Near the bottom of the snowpack, sugary facets exist in colder and dryer parts of the region, such as the far north.
Problems
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.