While the storm has eased somewhat, it isn't over yet. Dangerous conditions remain in the backcountry.
Confidence
Fair - Timing, track, or intensity of incoming weather is uncertain
Weather Forecast
Synopsis: The pineapple express will continue to bring good precipitation amounts to this region until Saturday but moves out on Sunday leaving dryer conditions.Friday night: 15-20 cm/mm snow/rain.Saturday: 10-15 cm/mm snow/rain expected. Freezing level around 1500 m in the morning, lowering through the day. Winds southwesterly up to 40 km/h.Sunday: Lingering light precipitation. Freezing level around 900 m. Light northwesterly winds.Monday: Dry, with some good sunshine. Cold in the morning, freezing level rising to 900 m in the afternoon. Light winds.
Avalanche Summary
Limited observations at this time, since very few people were in the mountains on Friday. On Thursday, natural avalanches up to size 3.5 were observed on north and south aspects from 1500 m to 2200 m.
Snowpack Summary
A heavy dump of moist new snow has increased recent storm totals to around a metre or more. The snow surface became wet as snow gradually turned to rain to approximately 1800 m in the south of the region and 1500 m in the north. As temperatures drop, expect to see a crust form at lower elevations. Strong southwest winds have redistributed the new snow into deep wind slabs on exposed lee slopes and cross-loaded gully features. The February 12 persistent weak layer (crust, and/or surface hoar) is now down 60-80 cm. It is primed for triggering and has been reacting readily to both natural and human triggers on all aspects and a wide range of elevations. Deeper persistent weak layers from early February and late January continue to show planar failures when moderate to hard forces are applied in snow pack tests. These deeper layers have not been reactive to the weight of a rider, but they could potentially be triggered during or immediately after the present storm system, further increasing the potential size of avalanche events.
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.