Regions
Northwest Coastal.
While avalanche danger will decrease in the wake of the storm I would make conservative terrain choices for a few more days until the snowpack has adjusted the recent load and warming.
Confidence
Poor - Due to the quality of field observations
Weather Forecast
A ridge will build over the weekend signaling an end to the deluge. Rain will continue overnight Friday with coastal regions receiving up to 10mm of rain and snow although this is expected to taper off rapidly further inland. The freezing level is forecast to drop to 1000m on Saturday with moderate westerly winds. Isolated showers may persist into Sunday although a clearing trend is expected as the winds become northwesterly, bringing scattered clouds and a freezing level of 750m. The region should be mainly dry by Monday when broken skies, light south west winds, and a freezing level of 1500m are expected.
Avalanche Summary
Warm temperatures, wind, snow and rain drove a natural avalanche cycle that started on Wednesday. Since then we have received reports of numerous natural and explosive controlled slab avalanches up to size 3 on all aspects above 1000m with widespread loose wet avalanche activity bellow . I am unsure if all of these avalanche were contained to the storm snow or if some may have released on one of the deeper week layers.
Snowpack Summary
Between 20 to 70 mm of precipitation in the form of new snow and/or rain had fallen through the storm as of Friday evening. In many places this sits on a thin layer of surface hoar that formed in the brief lull between systems on Febuary 10th. The freezing level rose to 1500m in the southwest corner of the region on Friday with cooler temperatures recorded further inland and to the north. Predominantly strong southwest winds have loaded lee features in the alpine and at treeline. Before this storm the late-January crust could be found down between 60 to 150cm in the south of the region and about half this depth in the north. This crust may have surface hoar on it. The mid-January rain crust and/or surface hoar layer is down over 160cm in the south and has generally become inactive. The November crust/facet combo near the bottom of the snowpack is still on my radar as a potential problem layer in the far north of the region.
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.
Wet Slabs
Wet Slab avalanches are the release of a cohesive layer of snow (a slab) that is generally moist or wet when the flow of liquid water weakens the bond between the slab and the surface below (snow or ground). They often occur during prolonged warming events and/or rain-on-snow events. Wet Slabs can be very unpredictable and destructive.