Regions
Northwest Coastal.
Storm slabs are very reactive to human triggers. Conservative terrain selection is crucial.
Confidence
High - Due to the quality of field observations
Weather Forecast
SUNDAY: Light flurries confined to coastal areas, 20-30 km/h south winds, alpine temperatures around -12 C.MONDAY: Cloudy with scattered flurries and 3-5 cm of new snow, 30-50 km/h south winds, alpine temperatures around -12 C.TUESDAY: Stormy with 15-20 cm of new snow, 30-50 km/h south winds, alpine temperatures around -12 C.
Avalanche Summary
On Friday, storms slabs were very reactive to human triggers producing numerous size 1-1.5 avalanches and widespread whumpfing and cracking in flat terrain. Explosive control resulted in numerous size 2-2.5 slab avalanches. A widespread natural cycle occurred during the peak of the storm with up to size 2.5 slabs on a variety of elevations and aspects. Conditions will remain touchy as the recent storm snow settles and stiffens.
Snowpack Summary
60-80 cm of recent storm snow has buried a variety of old snow surfaces including surface hoar, facets, crusts, stiff wind slabs and a melt-freeze crust below 1600 m. The storm snow has been very reactive on this interface including widespread whumpfing and cracking in flat terrain. Below this interface the snowpack is generally settled and strong with the exception in shallow snowpack areas around Bear Pass and Ningunsaw where basal facets remain an ongoing concern.
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.