Another torrent of heavy rain is expected across British Columbia’s South Coast as the latest atmospheric river brings warm air that’s also raising the avalanche risk.
Alyssa Charbonneau, a meteorologist with Environment Canada, says 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.
The weather office is maintaining a rainfall warning that covers Squamish, Whistler and other communities near Howe Sound, saying another 60 to100 millimetres is forecast before the rain eases to light showers Tuesday morning.
There may be some breaks in the heaviest rain, but Charbonneau says it’s a “cumulative event” and concerns about flooding stem from its long duration.
She says the systems are also carrying warm air that’s pushing up freezing levels, and the Avalanche Canada map shows danger ratings are high in many areas.
The danger is ranked at “high” in the south Chilcotin and Pacific mountain ranges, including Whistler and Pemberton, as well as northwestern B.C., and along the boundary with Alberta, stretching as far west as Nelson and Castlegar, B.C.
The forecaster says heavy rain soaks the snow, creating dangerous avalanche conditions, and travel into alpine areas is not recommended.
The avalanche danger is 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 ease somewhat by Tuesday.
B.C.’s River Forecast Centre is meanwhile maintaining flood watches 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 says a series of “potent” storms has delivered between 50 and 200 mm of rain through most of the region since Friday.
River levels are 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 forecaster downgraded the warning later on Sunday, saying water levels across the border were receding.
Charbonneau says 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 says.
Still, she cautions, 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.
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