Rising temperatures and intense solar radiation is the driving force for the Avalanche Danger Ratings on Saturday.
Weather Forecast
Saturday: The dominating ridge of high pressure will bring significant warming and sunny skies. Alpine temperatures could get as high as plus 3.0 degrees with freezing levels rising near 2300 m and sunny skies. Ridgetop winds will be light from the SW.Sunday: The ridge will start to weaken, allowing the next frontal system to move in. Skies will generally be cloudy and no significant precipitation is expected. Alpine temperatures will fall to -3.0 and freezing levels will be near 1100 m. Ridgetop winds will blow moderate from the SW.Monday: Unsettled conditions with snow amounts up to 5 cm. Ridgetop winds will be light from the SW. Alpine temperatures near -4.0 and freezing levels hovering at 1600 m in the afternoon.
Avalanche Summary
A natural size 2 slab avalanche was reported from the Southern part of the region. No additional information besides the size. On Thursday, reports from the Northern parts of the region, saw a natural slab avalanche size 2.5 from an East aspect at 2000 m, failing on the buried surface hoar layer from early January. This layer has been fairly quiet recently, goes to show it may still be reactive in isolated areas. Another noted size 2.0 slab avalanche failed on the recent buried weakness from a NNW aspect around 1600 m.Several rider triggered slab avalanches up to size 2.0 have been reported south of the Coquihalla. These avalanches were triggered from SE-E aspects at 1600-1700 m, failing on the most recently buried crust/surface hoar/facet layer.
Snowpack Summary
Wind slabs may be found on lee slopes (N-SW) behind ridges and ribs and may be touchy to rider triggers. This recent snow seems to be settling and gaining strength although forecast rising alpine temperatures and sunny skies will affect and weaken the upper pack.Down 10-30 cm sits a persistent interface comprising of crusts, facets and surface hoar crystals. Recently, this layer has been touchy in sheltered areas at treeline and below (where the surface hoar had a chance to form). Tests done on this layer have produced moderate-sudden planar and resistant planar results. This layer should remain on your radar through the weekend. Down deeper sits another surface hoar layer (40-80 cm) which seems to be gaining strength with very little reactivity on it.Near the base of the snowpack, a crust/facet layer exists, which is now unlikely to be triggered, except perhaps by heavy triggers in unsupported, shallow, rocky terrain where more faceting has taken place.
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.
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.
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.