Heavy snow, rain and high winds are forecast to wallop much of southern B.C. on Tuesday, creating dangerous driving conditions on mountain highways and high avalanche risk in the backcountry.

Environment Canada is warning winds up to 90 kilometres per hour will hit Vancouver Island and the Sunshine Coast today. Up to 70 millimetres of rain is forecast for the eastern Fraser Valley by Wednesday morning.

For inland areas, forecasters are predicting up to 25 centimetres of snow will fall in Whistler, the Okanagan, the Kootenay's and Columbia regions.

It was already raining heavily on Highway 1 in the Fraser Valley on Tuesday morning. (Lisa Johnson/CBC)

DriveBC has issued travel advisories for several mountain highways including the Coquihalla and the 97C connector, and the TransCanada Highway 1 between Boston Bar and Ashcroft, and between Revelstoke and Golden.

Between 40 and 75 centimeters of snow could fall on the Coquihalla Highway between Hope and Merritt, starting this afternoon and continuing overnight, according to DriveBC.

Environment Canada meteorologist Doug Lundquist says the alternative route up the Trans-Canada through the Fraser Canyon will not be much better.

"Even in Kamloops they're going to get five to 10 centimetres along the road between Kamloops and the canyon, and even that much can be a headache when it's about minus two," said Lundquist.

DriveBC is also warning the Trans-Canada highway between Revelstoke and Golden will be closed for intermittent avalanche control over the coming days.

Officials are asking people to consider delaying travel until the storm has passed later tomorrow.

The Canadian Avalanche Centre has issued a high danger rating for many backcountry areas in southern B.C.

As of 10 a.m. PT BC Ferries has not reported any sailing cancellations.