VIDEO: 'Pineapple Express' expected to take direct aim at Oregon

PORTLAND, Ore. (KOIN) — Thursday’s incoming round of rain marks the beginning of a week-long downpour that’s forecast to pick up in intensity over the weekend as an atmospheric river rakes direct aim at Oregon.

Thursday and Friday’s rainfall will pair with 20 to 30 inches of fresh snow in the Oregon Cascades. However, temperatures and snow levels will steadily rise through the weekend as an atmospheric river is forecast to channel warmer subtropical moisture into the Pacific Northwest.

The anticipated weather phenomenon, known as the “Pineapple Express,” occurs when a narrow band of moisture spans the North Pacific, funneling precipitation from Hawaii to the Western U.S. and Canada. Pineapple Express storms are known to bring heightened levels of rain and snow.

“Prevailing winds cross over warm bands of tropical water vapor to form this ‘river,’ which travels across the Pacific as part of the global conveyor belt,” the National Weather Service says. “When it reaches the west coast, the Pineapple Express can dump as much as 5 inches of rain on California in one day.”

If the weather pattern holds, Oregon will see its warmest and wettest stretch of the storm between Sunday and Tuesday, KOIN 6 Chief Meteorologist Natasha Stenbock predicts. KOIN 6 will continue to monitor the budding atmospheric river as it develops in the Pacific.