Regions
South Coast Inland.
Keep a close eye on the effects of the strong late-winter sun on Saturday, even brief periods of direct sun could initiate natural avalanche activity.
Confidence
Low - Timing or intensity of solar radiation is uncertain on Saturday
Weather Forecast
We are moving into a high and dry period for the foreseeable future. Northwest flow across the province will allow a couple of shortwave troughs to ripple along the upper flow giving a mix of sun and cloud. At this time, precipitation amounts will be insignificant.SATURDAY: Scattered cloud cover, freezing level rising to around 800 m, light north/northeast wind, trace of precipitation possible.SUNDAY: Scattered cloud cover, freezing level rising to around 1000 m, light west/southwest wind, no precipitation expected.MONDAY: Broken cloud cover, freezing level rising to around 800 m, light west/southwest wind, no precipitation expected.
Avalanche Summary
On Thursday wind loaded features produced natural avalanches to size 2.5. Several natural wind slab avalanches to size 2 were observed on steep north facing alpine terrain. Control work produced avalanches to size 2 in steep unsupported terrain.On Wednesday a natural size 1 wind slab was reported from an east facing feature at 1950 m. Isolated soft wind slabs were also being observed on steep convexities.Several small wind slab avalanches 15 to 25 cm in depth were susceptible to ski cutting Tuesday on north, northeast and east facing features between 1800 and 2000 m.
Snowpack Summary
The region picked up 10 to 40 cm of storm snow this week accompanied by wind mainly out of the southeast, south and southwest. As the storm exited the region Thursday winds shifted to the east/northeast. This new storm snow rests on top of old wind slabs that are becoming more stubborn and somewhat resistent to human triggering. The February 23 weak layer is now down 30 to 70 cm below the surface. This interface consists of wind hardened snow, facets, a sun crust on solar aspects and surface hoar that is present at and below treeline. Compression tests preformed Thursday continue to show planar results at this interface. The mid and lower snowpack are well settled and strong.Variable winds in the past month have created cornices on many alpine ridgelines. They will become touchier as they grow in size, as temperatures rise, and as the strong late-winter sun shines down upon them on clear days.
Problems
Wind Slabs
Wind Slab avalanches are the release of a cohesive layer of snow (a slab) formed by the wind. Wind typically transports snow from the upwind sides of terrain features and deposits snow on the downwind side. Wind slabs are often smooth and rounded and sometimes sound hollow, and can range from soft to hard. Wind 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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.