'Pineapple Express' weather drags heavy rain and floods to Pacific Northwest

NASA satellite images have shown an atmospheric river flowing into the Pacific Northwest, resulting in warmer temperatures and large amounts of rain, with flood warnings in effect.

The weather event is known as the 'Pineapple Express', and occurs when storms in the Gulf of Alaska pull moisture from Hawaii to Oregon and the rest of the Pacific Northwest.

Josh Cozart, a meteorologist at KOIN 6 said that Hawaii's warm, subtropical moisture made it all the way to Portland, which broke a temperature record at the start of the week.

"Portland actually broke a record for warmest Dec. 4 on record," he said. "Portland climbed to 65 degrees, breaking the old record of 59 last set in 1970."

But the storm will bring cooler temperatures by Thursday as it travels east and drags colder air from Alaska into the area Cozart said. 

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"The tail, or river, attached to the cinnamon roll shape is also a cold front that will eventually help work cooler temperatures back into the region," he explained.

With storm systems expected to bring heavy rains and strong winds across the West in the days ahead, forecasters have warned they could cause flooding, landslides, and coastal issues.

This stormy pattern is typical for the winter months in the West.

Mount Hood's ski slopes are getting rain instead of snow as a result of record-breaking temperatures in Oregon, with snowfall levels expected to remain above 9,000 feet until Wednesday.

The Mount Hood Meadows ski resort told KOIN 6 that if temperatures fall, they might be able to start the ski season on December 8.

Oregon and Washington are set to see rain and possible flooding. Fox Weather reports that several rivers across the region have been put on Flood Warnings. Some rivers near populated areas in the foothills of Western Washington are expected to approach or reach major flood stage by midweek.

Between 4-8 inches of rain have fallen in the mountains already, with much more anticipated.

Heavy rain and precipitation are expected to continue into late Tuesday before finally easing up in the evening as the band of moisture slowly pushes inland. But, local weather experts worry that "the stage has been set" for significant river flooding.

The FOX Forecast Center warns that the combination of several inches of rain on top of the 2-4 feet of snow already on the ground in the Cascades and the Olympics from winter storms over the weekend is causing extensive runoff.

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

Water levels are set to rise significantly on Tuesday, peaking either late Tuesday night or Wednesday. Moderate to major flooding is expected along the Skagit, Snohomish, Snoqualmie, and Skokomish rivers in Western Washington, with local communities warned to prepare for possible flooded roads and water entering buildings.

The Skagit River at Mt. Vernon is predicted to peak at 34.51 feet on Thursday, while the Snoqualmie River near Carnation is set to crest at 58.4 feet on Wednesday. Both these peaks are considered major flood stage.

The National Weather Service in Seattle reports that the region has already seen several inches of rain, with as many as 5 more inches expected over the Olympics, 2-4 inches over the Cascades, and 1-2 inches along the coast and over the interior lowlands by late Tuesday.

Moreover, Olympic National Park recorded a whopping 8.67 inches of rain. Duvall and Granite Falls, both near the foothills of the Cascades, also experienced heavy rainfall. Duvall had 7.12 inches, while Granite Falls saw 5.87 inches.

Skykomish, located in the heart of the Cascades along Stevens Pass, received just over 7 inches and counting.

What is a 'Pineapple Express' weather event?

The Pineapple Express isn't a surface storm, but an atmospheric river. The term "Pineapple Express" was coined by TV weathercasters in the 1960s, inspired by the popular fruit that has long been a symbol of Hawaii.

The "Pineapple Express" is a bit like El Nino, but instead of being a 'warm patch,' it's a huge, constant flow of warm, moist air that travels from the waters northeast of Hawaii to the West.

To be called a "Pineapple Express," the storm must start from the northeast of Hawaii.