Regions
South Coast Inland.
Storm snow amounts will vary across the region. The Coquihalla will see higher amounts then the Duffy. If your local riding area receives more than 25 cm of new snow consider the danger to be HIGH on Wednesday.
Confidence
Moderate - Intensity of incoming weather systems is uncertain on Wednesday
Weather Forecast
The Coquihalla can expect 5-15 cm overnight Tuesday accompanied by strong westerly winds. Less expected on the Duffy.Wednesday: 5-10 cm of new snow through the day with another 15-25 cm overnight Thursday. Strong southwest winds at ridgetop elevations. Freezing levels near 1200 m. Thursday: Another 10-15 cm expected tapering off throughout the day. Ridgetop winds light with strong gusts from the southwest. Freezing levels near 1400 m.Friday: A mix of sun and cloud. Alpine temperatures near -12 with a high of -4. Light-moderate ridgetop winds from the northeast and freezing levels at valley bottom.
Avalanche Summary
On Monday, no new avalanches were reported. Evidence remains of last weeks widespread avalanche cycle up to size 3.5 from alpine features, below rock bands and thin snowpack areas. Forecast new snow and wind will likely build new storm slab problems Wednesday afternoon into Thursday.
Snowpack Summary
Recent snowfall totals are highly variable. In the south, up to 40cm of snow fell in the alpine over the past three days, while tree line elevations saw 10-20cm. In the north, new snow totals were 15-20cm in the alpine, and rapidly decreasing below 1800m.In the alpine, winds were moderate to strong from the south / east (Coquihalla) and moderate from the south / west (Duffey zone), creating fresh wind slabs in exposed downwind (lee) terrain. At lower treeline and below, warm temperatures (and rain in many locations) have created heavy snow and tough riding conditions.The new snow adds to the 80-150cm of snow that fell during the last few weeks of January. These series of storms were accompanied by strong to extreme winds which resulted in extensive scouring and impressive cornice growth in upper elevation terrain. These accumulations sit on crusts from early and mid-January which generally show signs of bonding to the overlying snow; however, a week ago they were sensitive to human triggering. With forecast snowfall and strong winds this deeper instability may wake up initiation large and destructive 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.
Cornices
Cornice Fall is the release of an overhanging mass of snow that forms as the wind moves snow over a sharp terrain feature, such as a ridge, and deposits snow on the downwind (leeward) side. Cornices range in size from small wind drifts of soft snow to large overhangs of hard snow that are 30 feet (10 meters) or taller. They can break off the terrain suddenly and pull back onto the ridge top and catch people by surprise even on the flat ground above the slope. Even small cornices can have enough mass to be destructive and deadly. Cornice Fall can entrain loose surface snow or trigger slab avalanches.