6:30 AM PST UPDATE: New storm slabs may become increasingly reactive during the day.Be particularly cautious in wind-loaded areas and continue to make conservative terrain choices while the storm snow settles and stabilizes.
New snow overnight Wednesday will add to the 30-50 cm of recent storm snow which continues to be reactive, especially in wind-affected terrain at treeline and in the alpine. A poor bond may exist to the underlying old snow surface and reactivity may persist for longer than is typical.
Two weak layers consisting of a crust with small facets above buried between 50 and 180cm deep, have been responsible for a few large avalanches in the past two weeks. This problem seems to be more of an issue west of the Sea to Sky highway corridor. These layers are of greatest concern with large triggers, such as a cornice fall, or by first triggering a smaller avalanche that could step down to this interface.
On Tuesday, a few skier-controlled storm slabs were reported up to size 1, and previous old natural avalanche activity was seen from last weekend's storm.
On Monday, several natural storm slab and cornice failures were reported up to size 2. The cornice fall triggered a slab up to 50 cm deep from the slope below to size 2. Additionally, numerous explosive-controlled wind slab avalanches and cornices were reported up to size 2.
Looking forward to Thursday, natural avalanches are possible, and human-triggered storm slabs are likely, especially in wind-loaded areas. Storm slab reactivity is expected to persist for longer than is typical due to the weak surface they are sitting on.
For a deeper dive into conditions leading up to last weekend's storm, check out this awesome South Coast Conditions Report posted by Zenith Guides.
20 + cm of new snow may hit the region by Thursday afternoon. This will add to the 30-60 cm that accumulated over the past 5 days. In some areas, this new snow has bonded poorly to the underlying surface consisting of stiff wind slabs and facets formed by last week's wind and cold temperatures.
Deeper in the snowpack 60-180 cm down exists two crusts with facets sitting above them. They can be found in alpine and treeline elevation bands. These crust/facet layers have been responsible for a few large avalanches in the past 2 weeks in the Brandywine and Pemberton Icefield areas.
The remainder of the mid and lower snowpack is well-settled, strong, and consolidated.
Wednesday Night
New snow 10-20 cm. Alpine temperatures -10°C. Ridge wind southwest 50 km/h. Freezing level valley bottom.
Thursday
Snow up to 10 cm. Alpine temperatures -8 °C. Southwest wind 40 to 65 km/h. Freezing level 700 m.
Friday
Cloudy with sunny periods and a trace of snow. Ridgetop wind 25 to 50 km/h from the southwest. Alpine temperatures -5°C. Freezing level 700 m.
Saturday
A mix of sun and cloud with isolated flurries. Alpine temperatures near -5 °C. Ridge wind northeast 15 km/h. Freezing level 1100 m.
More details can be found in the Mountain Weather Forecast.
