Parts of the Pacific Northwest and British Columbia can’t catch a break. Atmospheric rivers, or plumes of deep tropical moisture, have brought excessive rainfall, flooding and mudslides over the past several weeks. The latest, perhaps the most intense yet, lashed the region with downpours and damaging winds Monday.
Some of the affected areas had seen more than three feet of water in the past month pushing river levels to all-time highs. Seattle had already clinched its third-wettest November on record and its wettest autumn on record is close to a lock.
British Columbia also got walloped with record rainfall, flooding and high winds. Tens of thousands were without power in the Canadian Province, roads were closed and the city of Merritt, home to more than 7,000 people, was mostly underwater and had been evacuated.
Some of the worst flooding in northwest Washington was reported in Whatcom County, across the border from British Columbia. Social media photos showed high water from overflowing creeks and rivers engulfing communities:
“I’ve lost track of how many road closures we’ve hit and detours we’ve taken — nothing compared to what so many folks are dealing w flooded homes and vehicles,” tweeted Michelle Esteban, a reporter KOMO News in Seattle.
The inclement weather forced closure of all schools in Bellingham, Wash. Officials cited flooded roads and dangerous driving conditions, “which impacts many staff, students and families and their ability to get to school and work safely.”
Significant river flooding was also reported in Skagit and Clallam counties to the south and southwest. The Weather Service in Seattle tweeted that four rivers in western Washington had reached record levels.
The Olympic National Park tweeted that heavy rains, flooding and landslides had closed numerous roads on the Olympic Peninsula.
Peak gusts topped 60 mph along the coast and 90 mph in the mountains in western Washington.
Moderate to heavy rain was falling over much of northwest Oregon, western Washington and southwest British Columbia on Monday afternoon.
Unlike most atmospheric rivers, which feature a longer-duration lighter, steadier rain, this one was dumping rainfall at impressive rates topping a half inch per hour.
In Custer, Wash., a stone’s throw from the Canadian border, 4.23 inches of rain was recorded Sunday. An additional 1.66 inches had fallen between midnight and 7 a.m. local time. The rain came along with winds gusting over 50 mph.
Incessant heavy rain will pile into the Pacific Northwest, USA 🇺🇸 & British Columbia, Canada 🇨🇦 in the next 72 hours due to a significant atmospheric river event.— Scott Duncan (@ScottDuncanWX) November 13, 2021
Flooding & landslides are highly likely. The atmospheric warmth & moisture can be traced all the way to the tropics. pic.twitter.com/h69BYT6YgQ
The atmospheric river was aimed directly at Vancouver, B.C., unleashing a fire hose of moisture that will stick around at least into the afternoon. Environment Canada, Canada’s equivalent of the National Weather Service, issued a rainfall warning for the city, stating that up to seven inches were possible in the city by Monday afternoon. The Fraser Valley could see as much as 10 inches, with “possible washouts, debris flow and pooling water” all possible.
Merritt, in interior southwestern British Columbia about three hours away from Vancouver, was placed under an evacuation order. Floodwaters had inundated two bridges and were threatening the third, and, with the city’s wastewater treatment plant rendered inoperable, mass sewage backups are possible.
This footage out of Merritt is heartbreaking.— Alanna Kelly (@AlannaKellyNews) November 15, 2021
The entire City of #Merritt is now under an evacuation order due to surging floodwaters from the Coldwater River.
The city’s mayor is urging residents to stay calm.@EmconServicesBC #BCFlood #BCStorm pic.twitter.com/k6R25Z61P2
Abbotsford, B.C., just north of the U.S. border and about 60 miles southeast of Vancouver, observed its wettest day on record Sunday with 3.95 inches falling.
The narrow but intense jet of moisture, originating from near Hawaii, is being slung east by an atmospheric squeeze play of sorts, with low pressure banked to the north and a high to the south.
The atmospheric river’s impacts will wind down by Monday evening in Washington state, but its final act could come with a burst of winds there and along the shoreline of Oregon, helping the system go out with a bang. High-wind warnings are up there through Monday evening.
Weather models indicate that Monday’s atmospheric river could rate Level 5 out of 5 on the scale devised by the Center for Western Weather and Water Extremes.
Atmospheric rivers carry the bulk of their moisture at the midlevels of the atmosphere thousands of feet above the ground, for which reason the greatest precipitation totals are realized in the higher elevations. Air forced up the mountains deposits its moisture on their windward side.
What’s to come
The atmospheric river will relinquish its grip on Vancouver after noon, and Seattle by 3 or 4 p.m. local time Monday.
“Additional rainfall totals of 2 to 4 inches across the lowlands and 5 to 10 inches across the mountains is expected with through Tuesday morning,” wrote the Weather Service in Seattle.
Coastal Oregon will see its effects only for a few hours as the decaying strip of juicy air swings southward and thins late Monday. By early Tuesday morning, it will be lapping at the Bay Area in California with some light showers, but areas to the south should see next to nothing.
Low pressure instigating the atmospheric river’s deluges will pass through southern British Columbia and Alberta on Monday night while intensifying en route to Saskatchewan. Strong high pressure will build in on its backside, the resulting pressure gradient, or change in air pressure with distance, spurring winds accelerating out of the west over the northern Plains and Montana, where high elevation wind gusts could top 100 mph.
Meanwhile, another storm system promises to bring more precipitation to the Pacific Northwest late Thursday into Friday.