Communities across British Columbia’s South Coast are gearing up for a series of storms forecast to deliver buckets of rain, and possible flooding.
Environment Canada has issued rainfall warnings for northern parts of Metro Vancouver along with Howe Sound, while rain-related weather statements are in place for Vancouver Island and the Sunshine Coast.
Forecasts call for up to 300 mm of rain on West Vancouver Island and the Coast Mountains, with Howe Sound expecting up to 250 mm and the Fraser Valley up to 120 mm. while parts of Metro Vancouver could see between 60 and 90 mm over the same period.
The rainfall is forecast to peak Sunday night into Monday. However, the exact timeline and locations that will be hit hardest by the systems remain uncertain.
The rain is being delivered by a series of atmospheric rivers, meteorological phenomena that transport warmer moisture from subtropical regions.
That warm airmass also has the BC River Forecast Centre concerned, because it is expected to raise freezing levels as high as 2,500 metres.
Forecast centre hydrologist Natasha Cowie told Global News the weather system looks set to be the “biggest precipitation event” of this fall and winter season.
“There’s going to be this parade of storms that come through with a pretty high rainfall total — we’re also expecting a fair bit of snowmelt, because the freezing levels are going to be rising a lot,” she said.
“We are anticipating up to anywhere between 50 and even as much as 150 mm of additional snowmelt over the weekend and into early next week that’s going to then be going on top of that runoff from the rainfall.”
The forecast centre has issued flood watches for the South Coast, including Howe Sound, the Sunshine Coat, the Sea-to-Sky region, the North Shore Mountains, the Fraser Valley and Vancouver Island.
High streamflow advisories are also in place for Lower Fraser River tributaries and the eastern Fraser Valley.
Cowie said there is also concern about the potential for slides, as the downpour and snowmelt combine to saturate soils.
On Vancouver Island, preventative measures are already underway, with BC Hydro spilling water from the John Hart Dam near Campbell River in anticipation of the downpour.
“When we do know that storms are coming and we think that we may not have enough capacity in our reservoirs, which is the dams, to absorb, we will do some controlled spilling in advance,” BC Hydro spokesperson Mora Scott explained.
Scott said the Crown corporation is closely monitoring water levels in a number of rivers on the island and in the Lower Mainland, but believes its reservoirs will have the capacity to absorb most of the precipitation.
In Tofino, where some of the heaviest rainfall is expected, Mayor Dan Law said residents are being warned to prepare their properties for potential flooding.
The community is also closely watching Highway 4 for landslides. The critical highway is the only road link between the west coast and the rest of the island, and has faced repeated closures since damage near Cameron Lake from a wildfire last June.
“I know that (the Ministry of Transportation) is very, very aware of that and they’ll be watching that closely, so we will see what happens,” he said.
Law said the town’s engineering department has been highly proactive about upgrading public works in response to storms, and may be out on the roads over the weekend.
“It’s going to be dark, it’s going to be wet — those people are out there for their communities,” he said.
“Drive slow, drive safe, and if you don’t have to drive don’t drive, stay off the roads.”
B.C.’s Ministry of Emergency Management and Climate Readiness said in a release late Thursday that the storms may also bring winds that could cause power outages, and the province’s River Forecast Centre is monitoring streamflow closely.
Cowie said people who live in flood-prone areas should know their routes to higher ground and have an emergency kit packed.
She also warned the general public to stay well back from fast moving water, and not to drive into any water they can’t see the bottom of.
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