Regions
South Coast Inland.
Snowfall amounts over the coming days vary between the north and south portions of the region. Light to moderate amounts of snow accompanied by wind will gradually raise danger ratings.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Friday
Weather Forecast
THURSDAY: Flurries, accumulation 5cm / Moderate to strong south wind / Alpine temperature -2 / Freezing level 1300mFRIDAY: Flurries, accumulation 10-15cm / Moderate to strong southwest wind / Alpine temperature -3 / Freezing level 1400mSATURDAY: Flurries, accumulation 5cm / Moderate southwest wind / Alpine temperature -4 / Freezing level 1000m
Avalanche Summary
There is no recent avalanche activity to report. On Thursday, wind slabs may remain reactive to human triggers at upper elevations. In northern parts of the region, the deeper February weak layers continue to present a low probability / high consequence scenario.
Snowpack Summary
On Tuesday the freezing level reached 2000+m. A subsequent freezing may have created a thin crust. 10-15cm of snow at upper elevations may now sit on this crust. Thicker wind slabs and large cornices likely exist in alpine terrain. A widespread thick rain crust forming last week up to 2100m is now approximately 40-60cm below the surface. In the north of the region, the February weak layers are 80-120 cm deep and include a buried surface hoar layer that recently produced a few persistent slab avalanches and a crust/facet layer that appears to be gaining strength. In the southern parts of the region, the lower snowpack is generally stable.
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.
Persistent Slabs
Persistent Slab avalanches are the release of a cohesive layer of snow (a slab) in the middle to upper snowpack, when the bond to an underlying persistent weak layer breaks. Persistent layers include: surface hoar, depth hoar, near-surface facets, or faceted snow. Persistent weak layers can continue to produce avalanches for days, weeks or even months, making them especially dangerous and tricky. As additional snow and wind events build a thicker slab on top of the persistent weak layer, this avalanche problem may develop into a Deep Persistent Slab.