Higher amounts of snow expected in the southern parts of the region; especially the Coquihalla area. Danger ratings reflect the higher snowfall accumulations.
Confidence
Fair - Intensity of incoming weather is uncertain on Tuesday
Weather Forecast
Monday overnight brings 5-10 cm of new snow. This is accompanied by strong South winds, and freezing levels near valley bottom. Tuesday: Snow amounts 15-25 cm. The Coquihalla could see 30-50 cm by Tuesday night. The Duffy will receive less. Ridgetop winds strong from the SW. Treeline temperatures near -5. Freezing levels near 500 m. Wednesday: Due to the convective weather pattern, scattered light-moderate snow accumulations are expected. Ridgetop winds moderate from the SW. Treeline temperatures near -8. Freezing levels valley bottom. Thursday: Cloudy in the morning, broken skies in the afternoon. Light afternoon flurries. Freezing levels valley bottom in the morning, rising to 800 m in the afternoon.
Avalanche Summary
No new observations reported on Monday. On Sunday, a size 3 loose avalanche failed naturally with solar warming on a south-east aspect in the Coquihalla area. A size 3 slab also failed on a north aspect, 1.5m deep and 100m wide. A few isolated avalanches were observed on Saturday in steep, rocky terrain. On Thursday, a natural loose moist avalanche cycle was observed in the Coquihalla region between 1400-1700m, with avalanches of size 2-3.5. A few slabs also released, with crowns of 50-60 cm. Explosives testing in the Duffey Lake area produced slab avalanches up to size 2.5 and skiers triggered very touchy storm slabs to size 1.5. Avalanche activity may increase again with solar warming on Monday, or with snow and wind on Tuesday.
Snowpack Summary
Forecast snow and strong SW winds will likely create new storm and wind slab problems. Last week's storm snow created slabs at all elevations, which appear to have gained strength. Large cornices loom and threaten slopes below. Crusts down 50-60 cm can be found on solar aspects in the Duffey Lake, Chilcotin, and Coquihalla areas. These exhibit moderate to hard, sudden results in snowpack tests.Deeper persistent weak layers are variable in distribution across the region. A crust/surface hoar/facet layer buried in early February, now down about 1.5m, is still is a key concern. It is especially prevalent on south-facing slopes above treeline, and all slopes below treeline. Although the likelihood of triggering this layer has decreased, the potential for surprisingly large avalanches remains.
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.
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.
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.