Drivers advised to avoid 'treacherous' mountain passes as winter storm grips southern B.C.

A spell of harsh, wintry weather is set to continue across the southern quarter of B.C. on Monday night and into Tuesday, bringing treacherous winter-storm conditions to key highways crossing the Interior and torrential rain nearer the coast.

Winter-storm warnings are in effect for the Coquihalla Highway, Sea to Sky Highway, Okanagan Connector and sections of Highway 3 with heavy snow and freezing rain in the forecast.

Environment Canada says conditions will be hazardous. The high-elevation roadways were expected to see up to 15 centimetres of fresh snow during the day as well as an additional 10 to 20 centimetres Monday night. There is also a risk of freezing rain on the Interior passes overnight.

"With this storm system coming in today, tonight, tomorrow, we are recommending that any non-essential travel be postponed because the highways are going to be so treacherous," Environment Canada meteorologist Lisa Erven said Monday.

• Find Environment Canada warnings here

A stretch of Highway 1 between Golden and Revelstoke is also under a winter-storm watch, with 25 centimetres of fresh snow forecast for the next 24 hours.

Snowfall warnings are in effect for parts of the central coast, West Kootenay and Okanagan Valley. Multiple flights were cancelled or delayed out of the Kelowna International Airport and Penticton Regional Airport because of the adverse conditions. 

Further west, milder weather means the winter storm will manifest as rain. Rainfall warnings are in effect for parts of Vancouver Island and the South Coast, including Metro Vancouver, the Fraser Valley and Howe Sound, as "a pair of moisture-laden" Pacific frontal system seizes the regions.

Erven said up to 90 millimetres of rain could cause localized flooding in low-lying areas before the system eases Tuesday.

The snow inland is not expected to relent until early Wednesday but Avalanche Canada's website shows the avalanche risk has decreased over most of B.C. — although it is ranked as high for sections of mountains across the Sea-to-Sky region and South Coast.

Stubborn winter weather has gripped much of B.C. since New Year's Eve. Power has been knocked out for more than 160,000 residents over the last week and avalanches have claimed at least three lives.