Regions
Northwest Coastal.
New snow, wind, warming, and rain will increase the avalanche danger on Tuesday. It's a good time to stick to conservative terrain.
Weather Forecast
TUESDAY NIGHT: 15-25 cm of snow, 60+ km/h south wind, freezing level up to 1200 m.WEDNESDAY: Another 5-15 cm of snow throughout the day, 60 km/h south wind, freezing level around 1000 m.THURSDAY: Linger flurries with another 5-10 cm, moderate southeast wind, freezing level up to 1000 m after an overnight freeze.FRIDAY: Mostly cloudy with isolated flurries, moderate southeast wind, freezing level up to 1000 m after an overnight freeze.
Avalanche Summary
On Monday, two large cornice falls were reported, one of which triggered a size 2.5 persistent slab avalanche on the February weak layer on a northeast aspect at 1600 m. Explosive control north of Stewart produced numerous size 1-2 wind slabs and cornices on north and northwest aspectsOn Wednesday, expect the new storm slabs to be touchy at higher elevations with the ongoing potential for deeper avalanches on the February weak layer.
Snowpack Summary
Strong winds and 20-40 cm of new snow will form fresh storm slabs above 1200 m. At lower elevations, rain will weaken the snow and release loose wet avalanches in steep unsupported terrain features. On shaded aspects above 1300 m, the new snow is burying 20-30 cm of old storm snow. Elsewhere, a mixture of crusts and moist snow surfaces exist from recent melt-freeze cycles. The late February persistent weak layer continues to be a concern for triggering large avalanches. This combination of crust and weak facets is now down 100-150 cm. Recent snowpack tests at the May Creek area found moderate sudden results on the layer on a east aspect around 1200 m. The layer could still be triggered by light loads in shallow weak spots.
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.
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.
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.