Vancouver weather: Flood risk rises as heavy rain pounds B.C.’s South Coast
Parts of Metro Vancouver could get up to 120 millilitres, with the heaviest rainfall Thursday night into Friday
By Cheryl Chan
Last updated 5 hours ago
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B.C.’s South Coast is in for more rain as a prolonged atmospheric river lingers over the region, increasing flooding concerns.
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Parts of Metro Vancouver, the Fraser Valley and the Sea to Sky region should brace for periods of heavy rain over the next two days, said Environment Canada, which issued several rainfall warnings Thursday.
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The heaviest downpours are expected Thursday night into Friday.
The North Shore and northeastern areas, including Coquitlam and Maple Ridge, are expected to receive between 80 and 130 millimetres of rain by Friday.
Metro Vancouver’s rainfall warning was upgraded from yellow, the lowest, to orange. Under Canada’s new colour-coded system, orange indicates severe weather likely to cause significant damage or disruption.
The Fraser Valley, including Abbotsford and Chilliwack, could see 100 to 120 millimetres of rain, with higher totals near the mountains.
Whistler, Pemberton and areas along the Sea to Sky Highway are forecast to receive about 75 millimetres.
Rainfall warnings for the Fraser Valley and the Sea to Sky remain yellow.
The agency also warns freezing levels near 1,500 to 2,500 metres could trigger snowmelt, which could exacerbate effects of the rain, leading to flooding, road washouts, water pooling and an increased risk of landslides.
On Wednesday, the B.C. River Forecast Centre issued a flood watch for the South Coast warning that more than 150 millimetres of rain could fall across the region by Friday.
The latest rainfall comes on top of about 100 to 120 millimetres at lower elevations and up to 170 millimetres over higher terrain over the last week.
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Earlier in the storm, a substantial amount of snow accumulated in the mountains, increasing the potential for rapid melting. Freezing levels are expected to remain elevated at around 2,000 to 2,500 metres — possibly reaching 3,000 metres in some areas — for much of the storm.
Rivers across the South Coast remained within their banks as of Wednesday, but rapid rises are expected as rainfall continues.
“River levels are already elevated and soil is saturated as the next round of the storm begins, which will likely mean a faster and more dramatic flow response,” said the centre.
The storm’s extremely long duration, heavy precipitation rates, and potentially significant rain on snow and snowmelt contributions all increase the flood hazard associated.
The flood watch is in effect for the North Shore, Metro Vancouver, Howe Sound, the Sea to Sky Corridor, the Sunshine Coast, and the Fraser Valley.
While Washington State is also expected to get heavy rain, overflow from the Nooksack River into the Sumas River watershed is unlikely, said the centre.
Environment Canada said heavy rain is expected to ease by midday Friday as a cold front moves into the Lower Mainland. Freezing levels should also drop to between 500 and 1,000 metres by Saturday.
