Regions
Northwest Coastal.
Conservative terrain use is essential. Rein in your exposure and avoid slopes that have consequences if they were to slide.
Confidence
Moderate - Timing, track, or intensity of incoming weather system is uncertain
Weather Forecast
We're expecting moderate snowfall in the forecast period but amounts are tapering off towards Thursday. TUESDAY: An additional 15-20 cm in the south and 5 cm in the north. Winds moderate (20 - 40 Km/hr) from the south. Freezing level 1100m in the south and 900m in the north. Alpine temperatures near +1 in the south and -2 in the north. WEDNESDAY: 5-15 cm snow in the south and 10cm in the north. Freezing levels around 1100m. Winds moderate gusting strong (40-80 Km/hr) southwesterly. Alpine temperatures +1 in the south to -3 in the north. THURSDAY: Scattered flurries with up to 5cm snow. Winds moderate (25-40 Km/hr) from the southwest. Freezing level 800m. Alpine high temperatures -1 in the south and -5 in the north.
Avalanche Summary
A widespread natural avalanche cycle with storm slabs and loose dry avalanches occurred on all elevations with steep aspects throughout the weekend.
Snowpack Summary
We've had a significant warming trend since the arctic outbreak, and a large storm snowfall gradient (25-35cm in the south ; 60-80cm near Stewart). The new snow fell with moderate to strong SW winds, and formed touchy soft slabs and wind slabs. Expect this new snow to bond poorly to all the windslabs (and a spotty layer of surface hoar and facets buried Jan 12th) that formed during last week's arctic outbreak conditions. The older wind slabs sit on a variable interface composed of hard wind slabs, weak surface hoar (Jan 5/6 layer) and faceted snow. If you're starting to think it's a dog's breakfast, you're right! With the recent new snow loading, the deeper slabs have remained reactive, especially on southwest facing features near ridge crests. Deeper in the snowpack, the Christmas surface hoar layer (buried 70-120 cm) is still preserved in some southern areas and has been reactive in sheltered areas and steep open features at treeline and below treeline. Lower elevations (below treeline) have moist snow below 1000m elevation, making for heavy and difficult riding.
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.