B.C.'s Highway 5, the Coquihalla, experienced heavy snow, slushy road surfaces and delays on Sunday between Hope and Merritt, and Environment Canada is warning drivers that more heavy snowfalls and icy conditions are expected overnight.

Greg Pierce, an Environment Canada forecaster, said there was about 40 cm of snow on the roads Sunday, with another 10 cm falling throughout the day. He said between 10 cm and 15 cm more could fall overnight.

Pierce said conditions should improve Monday, but for now, drivers should use alternate routes or delay their travel plans.

At about 8:30 p.m. PT, DriveBC reported that the Coquihalla southbound lanes were closed 15 km south of Kamloops because of an accident. It advised drivers to detour via Highway 1 or via Highway 8.

Earlier, on Sunday morning, the northbound lanes of the Coquihalla were closed at the Box Canyon chain-up area because of a crash.

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Conditions near the Coquihalla summit (left) were treacherous Sunday morning. Some vehicles, such as the semi trailer shown (right) were delayed trying to make it past the Great Bear Snowshed. (DriveBC webcams)

A travel advisory was also issued Sunday along Highway 5 between the Portia Interchange and Coldwater Road, where compact ice and "extremely slippery" conditions made travel treacherous.

Falling rock was also reported near the Coquihalla Summit throughout the day.

DriveBC asked drivers to use extreme caution, and to consider using alternate routes or delaying their plans.

With files from The Canadian Press