A powerful multi-day atmospheric river is battering coastal British Columbia, with officials warning that rivers across the Howe Sound region — including Squamish and Pemberton — could surge to levels not seen in decades.
In a press release, the River Forecast Centre announced it has upgraded to a Flood Watch for Howe Sound and the entire Sea to Sky Corridor, cautioning that moderate to very heavy rainfall is expected from Wednesday, March 18, through Friday, March 20 — with rapid and dramatic river rises likely to follow.
Sign up for news alerts from the Squamish Reporter
A Flood Watch means that river levels are rising and will approach or may exceed bankfull. Flooding of areas adjacent to affected rivers may occur.
According to the press release, the storm’s first wave dropped 100 to 120 millimetres of rain at lower elevations and 150 to 170 millimetres at higher elevations over the past four days. An additional 50 to 150-plus millimetres is expected through Friday, falling on ground that is already fully saturated.
Compounding the risk is the rapidly melting snowpack. With freezing levels expected to sit between 2,000 and 3,000 metres for the duration of the storm, rain is falling at elevations where significant snow has already built up. The press release noted that melt rates could reach the equivalent of 30 to 50 millimetres of water per day, adding a major surge to rivers already running high.
River Forecast Centre warned that river peaks could be prolonged, potentially stretching from Thursday into Saturday, with flows possibly reaching levels seen only once every 10 to 20 years — or higher — in the hardest-hit areas. Residents and drivers are urged to stay off flooded roads and avoid driving through washouts.
