Regions
Northwest Inland.
We're still working with quite a bit of uncertainty regarding the region's snowpack structure after last weekends storm. Avalanche danger may be higher than forecast in areas that see continued precipitation fall as rain on previously dry snow.
Confidence
Poor - Due to the number and quality of field observations
Weather Forecast
By the end of Saturday a series of frontal systems will have brought up to 35mm of precipitation to the northwest of the region and around 15mm to the area around Smithers.Rain is expected at lower elevations in the south.5-10 cm of snow is expected to have fallen in the alpine by Friday afternoon with the heavier snowfall concentrated in the north. The freezing level in the southern half of the region could be as high as 1500m but should remain close to valley bottom further north. Winds will be moderate from the southwest. Similar freezing levels are forecast for Saturday when northern regions could see another 5cm of snow with moderate southwest winds becoming westerly. A cooling and clearing trend is expected to begin on Sunday accompanied by light northwest winds.
Avalanche Summary
No new avalanche have been reported yet through this storm At least one one avalanche last weekend on the early February surface hoar and I suspect that some of the bigger ones that were reported may have stepped down to even deeper week layers. Given the uncertainty I would keep these layers in mind especially in areas that receive more snowfall through this system.
Snowpack Summary
Between 10 cm of new snow in the south of the region and 20cm in the north has fallen at upper elevations as of Thursday afternoon. This may sit on a thin new layer of surface hoar that was reported to be growing in the lull between the last two storms. A freezing rain crust may have formed on the surface at lower elevations. Deeper in the snowpack there are a number of weak layers although there is uncertainty about which of them are still players, and which are now dormant. The early-February surface hoar layer may not exist everywhere, but where it does it can be found buried between 30 and 70 cm down. The late January crust is probably down 75 to 150cm in the south of the region but is likely shallower in the north. The mid-January rain crust and surface hoar is probably down between 100 and 200cm. Finally, the crust/facet combination from November is near the ground.
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.
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.