Regions
Northwest Inland.
A couple of recent deep slab avalanches in the north of the region are keeping Alpine danger ratings elevated.
Weather Forecast
MONDAY: light flurries overnight becoming mainly cloudy through the day, moderate westerly winds, freezing level 1000m. TUEDSAY: partly cloudy, moderate southerly winds, freezing level 800m. WEDNESDAY: partly cloudy, moderate westerly winds, freezing level 1200m.
Avalanche Summary
A couple skier triggered wind slab avalanches were reported on Saturday. In the north of the region, deeply buried persistent weak layers in the alpine have recently woken up with several large avalanches releasing on basal facets in the last week. This weak layer has be reactive to skier triggering from a thin spots or heavy triggers such as a smaller avalanches and cornice failure.
Snowpack Summary
Settling storm snow overlies a melt freeze crust buried on February 12th that extends up to around 2000m elevation. This snow is reported to be bonding well to the crust. Moist snow can be found at lower elevations and on slopes that see direct sun. Recent winds have redistributed the surface snow at higher elevations. Older wind slabs can be found on east aspects while reverse loading may have loaded lee features on the west. The early January surface hoar/facet layer can be found between 50cm and 1m down and remains a concern. This layer seems the most reactive in the north of the region but may still be a problem in the south as well. Shallow snowpack areas in the east and north of the region have a weak base layer of facetted snow on or just above the ground.
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.