A complex and unpredictable snowpack exists. Avalanche Canada has released a Special Avalanche Warning for this region. Check out the details here: http://www.avalanche.ca/news/VRHTjCUAADQcpVdL/spaw-150324
Confidence
Fair - Due to the number of field observations
Weather Forecast
The next Pacific frontal system will reach the coast tomorrow. The front will affect most of the Interior through the forecast period. Wednesday will see light convective flurries, moderate ridgetop winds from the SW and freezing levels near 1500 m. For Thursday, precipitation amounts expected are 10-15 mm. Ridgetop winds will be strong from the SW and freezing levels rising to 2500 m. Warm air will remain over the region on Friday with freezing levels rising to 3000 m. Skies will show a mix of sun and cloud and ridgetop winds will be moderate-strong from the SW.
Avalanche Summary
On Monday, the region continued to see numerous natural slab avalanches up to size 2.5 from all aspects and 2000-2500 m in elevation. These avalanches were failing on a crust layer from mid-March and also stepping down to a deeper crust/facet layer from mid-February. Human-triggered storm slabs and persistent slabs remain a serious concern, especially in steep alpine terrain. Remote triggering slab avalanches from afar also remain a concern. If an avalanche does step down to the persistent weak layer, very large and destructive avalanches are possible.
Snowpack Summary
At higher elevations, 40-60 cm of dense storm snow sits over the mid-March interface which had included crusts, moist snow, wind affected surfaces, and/or old wind slabs. Anywhere from 25-60 cm of snow sits on the mid- March interface, which has recently been reactive as a storm slab. The mid- February persistent weak interface is now down 80-120 cm and continues to be very reactive, producing very large and destructive avalanches. In exposed terrain, strong SW winds had redistributed the new snow into wind slabs on leeward features. Snow surfaces are reported to be moist below around 1900 m.
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.
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.