Regions
Northwest Coastal.
The timing of the this weekend's big warm-up is difficult to forecast. If Sunday ends up being the warmer day, Sunday's avalanche danger may be higher than posted.
Confidence
Fair - Timing or intensity of solar radiation is uncertain on Sunday
Weather Forecast
Sunday: Clear skies / Light and variable winds / Freezing level at about 2000mMonday: Clear with increased cloud late in the day / Light to moderate southwest winds / Freezing level at about 1500mTuesday: Overcast skies with very light precipitation / Light westerly winds / Freezing level at about 1300m
Avalanche Summary
In recent days numerous loose wet, and wet slab avalanches were reported up to size 2 from steeper start zones at treeline and below treeline. A widespread natural avalanche cycle up to size 4 occurred over the past 5 days and deep persistent weak layers became overloaded, initiating very-large avalanches. In shallower snowpack areas, storm slab avalanches have stepped down to the December facet/ depth hoar layer. Natural avalanche activity will likely continue through the weekend with sunny skies and a rapid rise in freezing levels.
Snowpack Summary
A recent storm has brought 90+ cm or more to coastal regions forming thick storm slabs on leeward features. Warmer temperatures have helped to settle the recent snow, although the storm snow may continue to be touchy where it overlies surface hoar, crusts and/or facets buried on April 2nd. At lower elevations the snowpack has been saturated by rain and may exist as wet snow or a refrozen crust. Large cornices have formed and loom over slopes below.The early February crust/facet layer is down 150 - 240 cm. This layer has become overloaded by recent storm loading and is failing in some places resulting in very-large avalanches.
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.
Deep Persistent Slabs
Deep Persistent Slab avalanches are the release of a thick cohesive layer of hard snow (a slab), when the bond breaks between the slab and an underlying persistent weak layer deep in the snowpack. The most common persistent weak layers involved in deep, persistent slabs are depth hoar or facets surrounding a deeply buried crust. Deep Persistent Slabs are typically hard to trigger, are very destructive and dangerous due to the large mass of snow involved, and can persist for months once developed. They are often triggered from areas where the snow is shallow and weak, and are particularly difficult to forecast for and manage.
Loose Wet
Loose Wet avalanches are the release of wet unconsolidated snow or slush. These avalanches typically occur within layers of wet snow near the surface of the snowpack, but they may quickly gouge into lower snowpack layers. Like Loose Dry Avalanches, they start at a point and entrain snow as they move downhill, forming a fan-shaped avalanche. Other names for loose-wet avalanches include point-release avalanches or sluffs. Loose Wet avalanches can trigger slab avalanches that break into deeper snow layers.