A moisture-laden system, which will be rated as a Category 4 atmospheric river, is expected to bring heavy rainfall starting Friday, targeting the South Coast. This will be the first of the season to impact the region. Wind and rainfall warnings, as well as flood watches have been issued to alert residents of prolonged heavy precipitation and strong winds through the weekend.
Atmospheric rivers transport huge amounts of moisture, like rivers in the sky. This moisture can fuel heavy rains when it arrives on the coast.
General rainfall totals of 40-70+ mm are expected, with up to 100 mm of rain possible along the coastal mountains. Localized totals of as much as 200+ mm are possible along western and inland portions of Vancouver Island.
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Strong southeasterly winds up to 70 km/h will also impact areas of Vancouver Island, the Sunshine Coast and Metro Vancouver on Saturday, which could result in power outages and travel impacts, including ferries. There’s an increased risk of washouts, rockfall, and even landslides where the heavier rain falls.
Rain picks up Friday, with wet and windy conditions persisting through the weekend
Moisture from a low-pressure system will be funneled between a trough off the coast of B.C. and a ridge of high pressure across Oregon and California. A temperature clash will create favourable dynamics to draw up tropical moisture and steer it toward the South Coast.
The ridge to the south won’t allow the atmospheric river to slump south quickly, increasing rainfall totals across western Vancouver Island and the higher terrain across the Lower Mainland.
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Rain started Thursday overnight for the central and north coast, but by Friday morning, the entire coast will be engulfed in soggy conditions.
Rainfall warnings are in effect for western Vancouver Island ahead of this system’s arrival.
The rain will pick up in intensity across Vancouver Island on Friday afternoon, continuing steady through Saturday afternoon. Up to 150 mm may fall along the coast, with as much as 250 mm in the mountains.
The east side of Vancouver Island is slightly protected from the rain shadow effect, but could still expect 50-100 mm in places like Nanaimo and Campbell River. Meanwhile, Victoria is forecast to see 30-50 mm of rain, which could make for the rainiest event for the region since last February.
The Lower Mainland will see persistent rain on Friday through Sunday, with some heavier periods overnight Friday and into Saturday, especially for Squamish, and North and West Vancouver. Rainfall amounts will vary greatly, from as little as 50 mm in Delta, to upwards to 125 mm in downtown Vancouver, 100-150 mm in the Fraser Valley, including Abbotsford, and over 100-200 mm in North and West Vancouver.
Expect ponding on low-lying roads, however, and landslides could become a concern in areas like Highway 4 on Vancouver Island.
The winds will also be noticeable in the south, with gusts between 50-70 km/h expected on Saturday. This could impact travel, as well, and could result in localized power outages.
For some locations in the Lower Mainland and southern Vancouver Island, this atmospheric river will be bringing some of the heaviest rainfall accumulations since the November 2021 event, which shattered rainfall records over 48 hours and cut off vital transportation routes.
WATCH: Vancouver Island atmospheric river on the way
Be sure to check back for the latest weather updates across British Columbia this week.
With files from Tyler Hamilton, a meteorologist at The Weather Network