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Rivers rising, homes flooded in Washington as ‘Pineapple Express’ atmospheric river


SEATTLE – Rivers in Western Washington are overflowing their banks and flooding neighborhoods as an atmospheric river event known as a Pineapple Express drenched the Pacific Northwest for a second day.

Several counties across the region are under a Flood Warning and some rivers near populated areas in the foothills of Western Washington are forecast to be near or reach major flood stage by Wednesday.

Flooding in Washington’s Grays River Valley on Dec. 5, 2023.
(Washington State Dept. of Transportation)

Flooding in Washington’s Grays River Valley on Dec. 5, 2023.
(Washington State Dept. of Transportation)

The Skokomish River floods in Washington’s Mason County on Dec. 5, 2023.
(Washington State Dept. of Transportation)

A home is flooded from the swollen Stillaguamish River in Granite Falls, Washington on Dec. 5, 2023.
(Benjamin Jurkovich / Washington Weather Chasers)

A home is flooded from the swollen Stillaguamish River in Granite Falls, Washington on Dec. 5, 2023.
(Benjamin Jurkovich / Washington Weather Chasers)

A mudslide blocks Seattle’s Burke-Gilman Trail on Dec. 5, 2023
(Seattle Parks Department)

A mudslide blocks Seattle’s Burke-Gilman Trail on Dec. 5, 2023
(Seattle Parks Department)

The Snohomish County Sheriff’s Office shared this photo of a car that was stranded in high water on Tuesday, Dec. 5, 2023. The driver was safely rescued.
(@SnoCoSheriff/X)

Already, as much as 4-8 inches of precipitation have fallen in the mountains, and more is on the way before the event begins to wind down.

Amtrak suspended service between Seattle and Portland, Oregon, due to the extreme weather and a landslide.

Service is expected to be suspended until at least Thursday morning.

WHAT IS AN ATMOSPHERIC RIVER?

Flooding witnessed in Granite Falls, Washington

Videos from along the Stillaguamish River in Granite Falls, Washington, show water rushing across roads and vehicles trying to navigate through the flooding as the river nears a record-high crest.

They also show water entering homes due to the rapidly rising rivers in the foothills of the Cascades.

According to the King County Department of Natural Resources and Parks blog, the county’s Flood Warning Center was opened to monitor conditions and and has warned that road closures are possible after the Snoqualmie River rose to a Phase 3 flood level.

HOW TO WATCH FOX WEATHER

According to the blog, the river’s three forks was recorded flowing at 20,670 cubic feet per second (CFS) which surpassed the Phase 3 flood alert threshold of 20,000 CFS.

“At these flows, we could expect to see flooding across the entire Snoqualmie Valley,” the blog said. “Roads that could overtop include the Fall City – Carnation Road, portions of West Snoqualmie River Road, Northeast Tolt Hill Road, Novelty Flats Road and others.”

7 FACTS YOU SHOULD KNOW ABOUT FLASH FLOODS

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The heavy rain on Tuesday morning led to standing water on several Seattle-area highways and roads, including Interstate 5. 

The Snohomish County Sheriff’s Office shared a photo of a car that had become stranded in high water in Granite Falls, where nearly 6 inches of rain had fallen. The driver of the vehicle was safely rescued.

WHAT TO DO IF YOUR HOUSE FLOODS

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Washington State Patrol said on X that troopers had responded to more than a dozen crashes since midnight in Snohomish County, with multiple areas with standing water.

What is a Pineapple Express?

A Pineapple Express is when the jet stream dips to the south into the tropical Pacific Ocean near Hawaii, gathers warm, moist air and carries it across the ocean where it dumps heavy rain in either the Pacific Northwest or California.

And the air in Washington is indeed warm. Seattle recorded a temperature of 59 degrees early Tuesday morning, which already broke its old record of 58 degrees. Olympia, Washington, hit 63 degrees on Tuesday morning which is now its second-warmest December temperature on record. Snow levels are near 10,000 feet.

WHAT IS A PINEAPPLE EXPRESS?

The FOX Forecast Center says that the combination of record-warm temperatures and several inches of rain falling on top of the 2-4 feet of melting snow on the ground in the Cascades and Olympics from winter storms over the weekend is resulting in extensive runoff. 

Numerous rivers, creeks and streams are expected to reach flood stage – with major flooding possible in some spots.

Western Washington rivers rapidly rising

Flood Warnings cover several rivers across the Northwest. Moderate to major flooding is expected along the Skagit, Snohomish, Snoqualmie and Skokomish rivers in Western Washington, and communities along those rivers were told to prepare for flooded roads and water creeping into homes and other buildings.

The Skagit River at Mt. Vernon is expected to crest at 35.47 feet on Thursday, which is well above major flood stage at 32 feet. The Snoqualmie River near Carnation is expected to crest at 58.55 feet on Wednesday, which is just above major flood stage at 55 feet.

Major flooding is occurring along the Stillaguamish River at Arlington, reaching 20.90 feet. That’s also well above major flood stage at 19 feet, and just below its record crest at 21.2 feet.

FLOOD WATCH, WARNING AND EMERGENCY: HERE ARE THE DIFFERENCES THAT COULD SAVE YOUR LIFE

Flood Watches remain in effect for much of the Northwest

The National Weather Service in Seattle says several inches of rain have already fallen in the region and up to 5 inches of additional rain is possible over the Olympics, 2-4 inches over the Cascades, 1-2 along the coast and 1-2 over the interior lowlands by late Tuesday.

This will be on top of the already impressive rainfall totals reported in the region over the past 24 hours.

The Flood Watches have covered much of western Washington and Oregon for days, but have expanded to the south to include portions of Northern California, including Eureka, through Thursday.

Flood Watches include the cities of Bellingham, Seattle and Spokane in Washington. In Oregon, the cities of Portland, Eugene, Coos Bay and Medford are included in the Flood Watch. 

HOW MUCH FLOOD WATER DOES IT TAKE TO DAMAGE A CAR?

The NWS says Olympic National Park recorded 8.67 inches of rain. Duvall and Granite Falls, which are both near the foothills of the Cascades, picked up several inches of rain. Duvall recorded 7.12 inches while Granite Falls reported 5.87 inches. Skykomish, in the heart of the Cascades along Stevens Pass, was just over 7 inches and counting.

The bulk of the heavy precipitation is expected to wind down as we head into Wednesday. 

However, the flood risk will continue throughout the day as copious amounts of water continue to flow downstream. More rain is in the forecast later in the week but snow levels will return to more typical December levels, mitigating any future flood threat.



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