Environment Canada is warning of another torrent of heavy rain in southwestern British Columbia in the latest atmospheric river to wash over the region. People use umbrellas to shield themselves from the rain in Vancouver, on Monday, September 25, 2023. THE CANADIAN PRESS/Darryl Dyck
VANCOUVER – There may be some breaks in a series of atmospheric rivers that have been saturating British Columbia’s South Coast, but the concerns over flooding come from the “cumulative event,” a metrologist says.
Alyssa Charbonneau with Environment Canada said Monday that another torrent of heavy rain was expected across the region, bringing warm air that’s also raising Avalanche Canada’s danger ratings in several popular backcountry areas.
The heaviest downpours are expected over Howe Sound and the Sea to Sky area, although the whole region will see more rain in coming days, Charbonneau said.
The weather office maintained a rainfall warning on Monday covering Squamish, Whistler and other communities near Howe Sound, saying another 60 to100 millimetres is forecast before the rain eases to light showers Tuesday morning.
Charbonneau said the systems are also carrying warm air that’s pushing up freezing levels, and a bulletin from Avalanche Canada on Monday said rain has saturated and weakened the upper snowpack in several mountain ranges.
The danger is ranked at “high” in the south Chilcotin and Pacific mountain ranges, including Whistler and Pemberton, as well as northwestern B.C.
The forecaster downgraded the rating to “considerable” in mountains in southeastern B.C. and along the boundary with Alberta later on Monday.
The danger is also classified as “considerable” in mountains throughout the Fraser Valley and parts of the central Interior, while it’s ranked at “moderate” along the North Shore mountains, the Sunshine Coast and parts of Vancouver Island.
The forecaster’s map indicates the risk is expected to remain high Tuesday in the south Chilcotin and Pacific ranges, including the Garibaldi area around Whistler.
B.C.’s River Forecast Centre has maintained flood watches for rivers and streams for all of Vancouver Island and the South Coast, including parts of the Fraser Valley, while lower-level streamflow advisories are in effect for the Central and North coasts.
A bulletin from the centre on Monday said a series of “potent” storms has delivered between 50 and 200 mm of rain through most of the region since Friday.
River levels were expected to peak in most areas on Monday and Tuesday.
The centre had issued a flood warning for the Sumas River as the nearby Nooksack River in Washington state swelled over its banks, but the centre downgraded the warning later on Sunday, saying water levels across the border were receding.
Charbonneau said the rain is expected to persist until some time in the middle of the week, perhaps Wednesday night, before easing up.
“We do see things cooling down toward seasonal, and it does look like we’re going to have a stretch of dry weather through the weekend,” she said.
Still, she cautioned, the longer-term forecast for B.C.’s South Coast should be taken “with a grain of salt” at this time of year because it can change quickly.
This report by The Canadian Press was first published Jan. 29, 2024.
