Regions
Northwest Coastal.
Storm slabs are very reactive to human triggers. Conservative terrain selection is crucial.
Confidence
Moderate - Due to the number of field observations
Weather Forecast
We're looking at occasional flurries and cool temperatures throughout the forecast period. MONDAY: Cloudy with scattered flurries and up to 3-5 cm of new snow, 30-50 km/h south winds, alpine temperatures around -10 C. TUESDAY: Flurries with 5-10 cm of new snow, 20-40 km/h south winds, alpine temperatures around -11 C. WEDNESDAY: Light flurries, 20-30 km/h south winds, alpine temperatures around -12 C.
Avalanche Summary
On Saturday several storm slabs sized 1.5 to 2.5 (some remote triggered) were reported on north through east aspects, between 1100 and 1400m elevation. On Friday, storm 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
Another 5-10cm of low density snow falling Saturday overnight into Sunday has brought recent storm snow totals to 60-85 cm. All this 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 resulting in widespread whumpfing and cracking in flat terrain, and sudden, propagation-likely test results. 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.