Caution should be used when venturing into big terrain. Buried weak layers are still capable of producing large destructive avalanches.Daytime warming may push the hazard higher than forecast.
Confidence
Fair - Due to the number and quality of field observations
Weather Forecast
5 to 10cm of cm throughout the day today, then another light pulse of moisture through Sunday evening and into Monday morning. Monday afternoon the skies should clear and bring sun to the South Coast Inland region. Daytime heating will bring the freezing level up to around 1500m for the forecast period, then climb to over 2000m later in the week.
Avalanche Summary
Moist loose avalanches reported on solar aspects below 1900m. No other reports from the area.
Snowpack Summary
20-30 cm of low density storm snow is sitting on a strong and supportive rain crust that was buried last Saturday and extends as high as 2100m. West through southwesterly winds have shifted these new accumulations into touchy wind slabs in exposed lee terrain, especially high NE aspects. A facet/crust persistent weakness that was buried in mid-March is now approximately 50-100 cm down. In recent snowpack tests, it was found down 55 cm near the Duffey Lake Road and produced moderate sudden results. This remains the chief concern amongst avalanche professionals in the region because of it's potential for very large avalanches.
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.