B.C. forecast centre issues flood warning for part of Lower Mainland amid atmospheric rivers

British Columbia's River Forecast Centre issued an upgraded flood warning for the Sumas River, a tributary of the Fraser River east of Vancouver on Sunday.

An updated bulletin says flows in the Sumas River are not anticipated to pose a hazard for flooding into Sumas Prairie, an area that was hard hit during the atmospheric rivers that swamped much of southwestern B.C. in November 2021, washing away bridges and spurring landslides that killed five people.

But in neighbouring Washington state, the bulletin says high flows on the Nooksack River have reached "local flood stage.''

It says "spillover'' into the Sumas River watershed has been observed near the community of Everson, Wash., about 20 kilometres south of Abbotsford.

The centre says the spillover should be "short-lived'' as upstream areas of the Nooksack have already reached peak levels and are now receding.

Sunday's bulletin says the latest round of atmospheric rivers has delivered between 50 and 160 millimetres of rain throughout the South Coast since Friday, and forecasting suggests two more will arrive by Tuesday.

A special weather statement from Environment Canada says snowmelt from above-seasonal temperatures is adding to the potential for flooding and landslides.

An updated bulletin from the weather agency says the heaviest rain is expected on Monday, but the rainstorms could last until the middle of the week.

The statement spans all of Vancouver Island, Metro Vancouver and the Howe Sound region, as well as the Sunshine Coast.

It says the rains combined with mountain snowmelt raises the risk of landslides in "vulnerable areas'' as water falls on

already-saturated surfaces.

The River Forecast Centre says the heaviest rainfall is expected over western Vancouver Island and the Coast Mountains.

Flood watch for Island and South Coast

The centre is maintaining flood watches for the island and much of the rest of the South Coast, including the Sunshine Coast, Fraser Valley and Sea-to-Sky region.

Today's update says rivers with potential for flooding on the island include the Gold, Salmon, Somass, Englishman, Qualicum, Chemainus and Cowichan rivers.

On the mainland, it says rivers with potential for high flows and flooding include the Stawamus, Squamish, Mamquam and Cheakamus rivers, as well as tributaries around the North Shore mountains, the Fraser Valley and the Sunshine Coast.

Meanwhile, a lower-level streamflow advisory is in effect for the Central Coast.

Environment Canada added a rainfall warning for Kitimat, saying the community could receive up to 75 millimetres of rain by Tuesday morning.

A wind warning also spans Prince Rupert and Haida Gwaii, where the weather office says gusts could reach speeds of 110 kilometres per hour before easing Monday.