Regions
Northwest Coastal.
Danger ratings will be one level higher in areas that receive more than 20 cm on Thursday.
Confidence
Fair - Timing, track, or intensity of incoming weather system is uncertain on Thursday
Weather Forecast
Synopsis: The pattern switches to a NW flow for the forecast period opening the door for some cooler dryer snow and potentially strong winds.Thursday: Freezing Level: 300m Precip: 10/15mm 10/20cm Wind: Mod, WestFriday: Freezing Level: 900m Precip: Trace Wind: Mod gusting Strong NWSaturday: Freezing Level: 500m Precip: 2/3mm 4/6cm Wind: Light, NW.
Avalanche Summary
Numerous size 2-3 avalanches have been running naturally and with explosive assistance throughout the region. Large avalanches have been running on all aspects, with the bulk of the activity occurring on N - SE facing aspects. The activity likely calmed down a bit on Wednesday as temperatures dropped.
Snowpack Summary
Heavy wet snow has fallen at upper elevations with freezing levels rising to 1500m during the last storm. Strong west winds have transported the new snow creating storm slabs that sit above a weak layer formed during the last cold snap. Surface hoar, and facets in the upper snowpack are now buried anywhere from 50 to 80cm from the surface by the recent stormShames area at 950m elevation suggested the mid and lower snowpack was composed of various faceted layers and a stiff 4 cm crust. Another crust can be found closer to the base of the snowpack. The recent precipitation will strengthen the snowpack at lower elevations, but may prove to be problematic with rapid wind loading at upper levels.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.