Next entry in B.C.'s atmospheric river parade will pack a punch

The next B.C. atmospheric river will pack a wallop, expected to produce high rainfall totals across the Lower Mainland and the Fraser Valley.

Totals since Sunday have topped 70 mm in portions of the South Coast; the next round of torrential rainfall threatens over 100 mm across the Fraser Valley, further increasing the threat of localized flooding.

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On Wednesday, there’s more concern for more intense, high-elevation snow across eastern B.C. We have an additional 10-20+ cm forecast across higher terrain.

With that, expect hazardous travel along the mountain passes as they face copious amounts of snowfall.

Heavy rain, snow continues as next atmospheric river pushes through

Highest rainfall reports through Tuesday morning include:

• Port Mellon: 70 mm

• Coquitlam: 62 mm

• Squamish: 57 mm

By Tuesday night, the next wave of moisture arrives across the South Coast, producing rainfall rates up to 3-5 mm an hour as the atmospheric river stalls in the eastern Fraser Valley and Washington state on Wednesday.

Rainfall totals with the next wave will likely reach upwards of 40-50 mm for downtown Vancouver and 75-100+mm for the eastern Fraser Valley. Greater Victoria is likely recording 30-50 mm of rainfall.

By Thursday, the stream of moisture slumps south, with showers dissipating through the morning.

Once again, heavy snow targets the Interior mountain passes through Wednesday.

• Pine Pass: 20-30 cm

• Rogers Pass (Trans-Canada Highway): up to 20 cm

• Kootenay Pass/Paulson Summit: up to 20 cm

Flood risk

The peak flood risk is expected late Wednesday into Thursday. Fraser Valley rivers could reach five- to 10-year flood levels, or higher. The main impacts include riverbank erosion, submerged roads and an elevated landslide risk.

• Flood watch: Lower Fraser and Skagit

• Chilliwack, Skagit, Coquihalla Rivers

• Abbotsford, Chilliwack, Hope

• East through Manning Park

• The Sumas River is also at risk due to possible Nooksack River spillover

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High streamflow advisories

• Tulameen River

• Coldwater River

• Central Coast (Kingcome, Wannock)

• South Coast, including Metro Vancouver and North Shore

• Vancouver Island

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Also an issue is the Nooksack River flood risk rising in Washington state. There is a 13 per cent chance of an exceeding flood spill threshold. It could push floodwaters into the Sumas River system.

Luckily, a dry pattern over the past week will give some breathing room for the watershed.

Long-range outlook looking very active and mild

Beyond, above-seasonal temperature will continue to dominate across southern B.C. through mid-December, and passed that. No persistent, frigid weather is in sight.

A very active pattern will continue for the South Coast region well into the second half of December, with above-normal precipitation totals. Very heavy snow is forecast for the alpine regions, but snow levels will often be on the high side of normal with rain at the bases of the ski areas.

Stay with The Weather Network for the latest on conditions across British Columbia.

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