The Pacific Northwest is bracing for what meteorologists are calling an “atmospheric river,” a stream of water vapor due to arrive from the Pacific on Sunday evening and bring heavy rain and flooding on Wednesday.
The main impact of the storm system was expected in the mountains of northern Oregon and western Washington, where up to seven inches of rain can inundate rivers flowing from mountain ranges, said Dustin Guy, meteorologist for the National Weather Service in Seattle.
“These amounts, combined with fairly high levels of snow, can significantly increase water levels in our rivers,” Mr Guy said.
It was too early on Sunday afternoon to know which rivers might be the most flooded, Mr Guy said, so the weather service had yet to issue any flood warnings.
Parts of Oregon and Western Washington had winter weather warnings in place as heavy rain was expected from Sunday evening through Tuesday morning. Seattle weather service. Lighter rain is forecast for Wednesday, with possible flooding starting late Monday or Tuesday.
Gusty winds and “distant, energetic ocean waves” are expected along the coast. Weather service in Portland, Oregon.
You thought winter was over, didn’t you? Seattle Weather Service reports. Twitter on Sunday morning. “Well, it’s not.”
Mr Guy said it was “definitely not unusual” that there is an atmospheric river in the west at this time of the year, with only a few weeks left before the end of the rainy season.
An atmospheric river is a trail of water vapor that moves through the sky in much the same way that a river moves through the earth. National Oceanic and Atmospheric Administration.
Think of it as “a long ribbon of very humid air pointing right at us,” Mr. Guy said.
This week’s atmospheric river will be at least the second to hit the western United States in the past few months.
In October atmospheric river converged with a bomb cyclone cause heavy rainfall in the San Francisco Bay Area. Nearly 100,000 customers lost power due to landslides and hazardous road conditions in areas of Northern California.