How does one atmospheric river impact one region more than the other? It all depends on the axis of the moisture and how long it sticks around. The atmospheric river moving in this week will stay tilted to the north, mainly impacting Washington state and Vancouver Island, British Columbia.
Weather models are projecting anywhere from an inch to two inches in the northern Oregon region, with totals across Washington up near the Olympic Peninsula in the two- to the four-inch range.
Most parts of Metro Vancouver and the Fraser Valley are expected to see 75 to 100 millimeters (3 to 4 inches) of rain, reports CTV News Vancouver.
“Heavy rain will develop early this afternoon as the first system arrives and continue until Wednesday afternoon as additional systems impact the coast,” a warning posted by Environment Canada Tuesday morning said.
“The heaviest hit areas of Metro Vancouver are going to be the North Shore mountains. That’s where you could see easily 150 millimeters (six inches) or even more of rain,” said Bobby Sekhon, of Environment Canada.
Rivers near flood stage with the threat of melting snow
There are some flood watches already out in Washington, but Oregon, expected to get lesser amounts of rain, is free of any flood alerts. There are only a select few locations in Oregon that are still in the near flood stage at this time.
Washington is in a different boat, as the Chehalis river is still running very high in many locations. That is why the flood watch is in place for that area of Washington this week. The atmospheric river will bring in some more rain and likely additional flood warnings this week.
In a prepared statement released Monday afternoon, Emergency Management B.C. said “the rainfall expected this week, combined with the melting of recent snow is a concern. Rivers are expected to rise, resulting in possible flooding. Previously flooded areas may be more vulnerable.”
Heavy rain is expected for coastal areas including east and west Vancouver Island, Fraser Valley, Howe Sound, inland Vancouver Island, Metro Vancouver, and the Sunshine Coast.
A wind warning is in effect for the central coast – coastal sections, Haida Gwaii, North Coast – coastal sections, and North Vancouver Island.
The River Forecast Center has issued a high streamflow advisory for: Howe Sound; Sunshine Coast; Sea-to-Sky; North Shore Mountains; Metro Vancouver; Fraser Valley, including the Chilliwack River and surrounding tributaries; and Vancouver Island (North, East, South, West, and Central).
The Rain Forecast Center says “The upcoming temperatures are not forecast to be as warm as the atmospheric river events in November,” but warned of “added vulnerabilities due to erosion and higher baseflow conditions” in areas still recovering from the mid-November floods.
