Atmospheric river to bring heavy rain to B.C.'s South Coast, orange warning issued for Fraser Valley

An atmospheric river headed toward the B.C.'s South Coast will bring significant rainfall to parts of the Lower Mainland.

The storm has prompted Environment and Climate Change Canada to issue an orange warning, under its new colour-coded warning system, for parts of the Fraser Valley.

People living in the central and eastern Fraser Valley — including Chilliwack, Hope, and western sections of Highway 3 from Hope to Princeton — can expect rainfall amounts between 70 to 100 millimetres between Tuesday night and Wednesday evening.

"Warm air with the system will cause freezing levels to rise and snowmelt combined with the already saturated ground and heavy rain, will likely result in high streamflows and localized flooding," the warning reads.

Metro Vancouver and the western portion of the Fraser Valley, and much of the west coast of Vancouver Island, are under a yellow warning, with forecasters predicting between 50 to 80 mm of rain to fall in those areas.

Drivers are warned that visibility may be poor at times and that water may pool on roads and in low-lying areas.

The B.C. River Forecast Centre has issued a flood watch for lower Fraser River tributaries through the Fraser Valley and into the southern Interior, including Abbotsford, Chilliwack, Hope, the Sumas River, Skagit River and Coquihalla River.

A flood watch is the second level on the provincial forecast centre's three-tiered warning system. It means that river levels are rising, and flooding in areas adjacent to riverbanks may occur.

A high streamflow advisory is also in place for the central coast and south coast, including Howe Sound, the North Shore Mountains, Metro Vancouver and Vancouver Island. This means that river levels are rising or expected to rise rapidly in these areas, but no major flooding is expected.

The province said rainfall amounts have been “unusually high” for this time of year with up to 100 millimetres of rain in the last 24 hours. 

People are urged to stay clear of fast-moving waterways and avoid driving through flooded roads as rivers are expected to continue rising through Thursday.

Environment Canada updated its weather warning system last month with a risk-tiered colour-coded system that aims to offer a clearer picture of the weather's impact — and indicate how the public should prepare.

The alert level will be based on an assessment of both the potential impacts of the weather event and also the forecast confidence.

The changes align with recommendations from the World Meteorological Organization and follow updates already implemented by 31 weather agencies across Europe.