What to expect as latest atmospheric river drenches B.C.'s South Coast

Another atmospheric river is drenching B.C.'s South Coast this week – but so far, there hasn't been enough precipitation to prompt any rainfall warnings.

Environment Canada meteorologist Doug Lundquist said the storm is packing subtropical moisture, having originated north of Hawaii, and might lead to some clogged culverts and other minor flooding in the Lower Mainland.

But the system is expected to pass through quickly enough that no major impact is anticipated, at least on this side of the Canada-U.S. border.

"If there's one area I'd be worried about, it's south of the border, so down towards Washington and Oregon," Lundquist told CTV News. "And even there, they're only expecting minor impacts."

Environment and Climate Change Canada is forecasting 10 to 20 mm of daytime rain on Thursday, with periods of heavier downpours expected later in the evening.

But there are some areas of concern in the region.

The River Forecast Centre has issued a high streamflow advisory for the Fraser River from Quesnel downstream, and from Hope to the ocean, meaning minor flooding is possible in low-lying areas.

The advisory, which was prompted by increased snowmelt along with the "moderate" rainfall, indicates lower risk than a flood watch or flood warning.

Until the storm clears, the Fraser Valley Regional District urged the public to keep away from "fast-flowing rivers and potentially unstable riverbanks." Residents living in floodplain areas, particularly those that aren't protected by dikes, have also been advised to keep an eye on water levels.

There are also more serious flooding concerns on rivers outside of the Lower Mainland. 

Speaking over the phone from the B.C. Interior, Lundquist noted June's soggy weather also serves a purpose in preventing the kinds of wildfire seasons the province has suffered in recent years.

"It's an important part of what we do need for this time of year, to provide rains to the Interior so we don’t get fires and smoke coming out to the coast in the summer," he said.

The atmospheric river is more potent than B.C. normally sees heading into summer, but not all that unusual, according to the meteorologist, who also voiced his dislike for the term "June-uary."

"January is actually much wetter than this. This is just one system in June, and June is typically wet," he said. "This is normal, so why don't we call it June?"

Lundquist also stressed that atmospheric rivers don't necessarily equate to disastrous flooding, the likes of which B.C. suffered last November, when one of the systems delivered a month's worth of rain over just a few days. Environment and Climate Change Canada has said it's working on a system of ranking atmospheric rivers, though it's unclear when it will launch. 

"We have anywhere from 20 to 30 of these every year in the western part of North America," Lundquist said. "We've got to take it in context. This one isn't even wet enough to provide for a warning."

With files from CTV News Vancouver's Ben Nesbit