Regions
South Coast Inland.
Fresh snow fall and westerly winds Tuesday will likely form a new round of shallow wind slabs that rest above wind slabs formed over the weekend. Seek out wind sheltered terrain where you can avoid the wind slab problem and find the best riding.
Confidence
Low - Timing, track, or intensity of incoming weather system is uncertain on Wednesday
Weather Forecast
A weak upper trough Tuesday should deliver a small shot of precipitation and wind before a vigorous low makes landfall on Wednesday which has potential to bring significant precipitation. Unfortunately the weather models have not yet agreed on a solution with regard to track and intensity, but there will likely be less uncertainty as we get closer to Wednesday. Stay tuned for more details. TUESDAY: Broken cloud cover, freezing level beginning at valley bottom rising to around 500 m in the afternoon, moderate to strong west wind, 1 to 5 cm of snow.WEDNESDAY: Overcast, freezing level around 1000 m, potentially strong to extreme south/southwest wind, latest model run shows about 10 cm of snow. Stay tuned for more details. THURSDAY: Scattered cloud cover, freezing level around 1300 m, light to moderate southeast wind, 1 to 5 of snow possible.
Avalanche Summary
On Sunday wind slabs up to size 2 were sensitive to skier triggering on northeast, north and northwest facing features between 1950 and 2100 m. Small wind slabs failed naturally and were human triggered Saturday to size 1 on south and southeast facing features between 1750 and 1900 m.
Snowpack Summary
20 to 40 cm of new snow fell over the weekend accompanied by strong winds that were predominantly out of the south, southwest and west. This wind event formed widespread wind slabs that likely extend down into treeline. The new snow rests on the February 23 weak layer that consists of wind hardened snow, facets, a sun crust on solar aspects and surface hoar that is present at and below treeline. In the southern portion of the region a widespread crust is down 40 to 80 cm below the surface. Well-consolidated snow exists below the crust.Variable winds in the past month have created cornices on all aspects in the alpine. 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.