See what's behind Pineapple Express as it drenches California and Northwest
This story was updated to correct spelling in headline.
An atmospheric phenomenon called a Pineapple Express is expected to bring heavy rains and snowfall to California and the Northwest this week.
What is a Pineapple Express? It's a type of atmospheric river that forms a long, narrow tract in the Earth’s atmosphere. This jet stream gathers moisture from the tropics near the equator and sweeps it toward the poles. It originates near Hawaii.
Accuweather meteorologists predict this atmospheric phenomenon could bring strong winds, heavy rains and landslides.
How a pineapple express can wreak havoc on the West Coast
In the West, atmospheric rivers approach from the Pacific Ocean, where they’ve collected tremendous amounts of water. They occur most often when the El Niño weather pattern is in force in the Pacific.
The long, narrow corridors of air, which are heavy with moisture, form when warmer air from the tropics in the lower latitudes moves toward the poles ahead of powerful storm fronts. These "rivers in the sky" have been responsible for as much as 65% of the West's extreme rain and snow events, a 2017 study said.
Unable to view our graphics? Click here to see them.
Rivers in the sky
AccuWeather warned of possible flooding, avalanches, strong winds and travel delays as excessive rains move across California. Several cities, including San Francisco and Redding, could receive a month’s worth of rain.
Landslides and mudslides are possible from the top of California to San Francisco, AccuWeather meteorogist Heather Zehr said. That could lead to road closures and travel disruptions.
Excessive wet weather could bring risks of flooding in California
The valley and foothills will be under a flood watch until Tuesday evening, according to the National Weather Service. By early Tuesday, snow was expected in the Sierra Nevada at elevations above 6,000 feet. Travel in the Sierra Nevada probably will be hampered by strong winds and the rapid accumulation of snow.
The National Weather Service Climate Prediction Center predicts below-normal temperatures in California for the next eight to 14 days. With the exception of Southern California, which is predicted to get near-normal or below-normal precipitation, much of the state will experience above-average precipitation.
CONTRIBUTING John Bacon
SOURE National Oceanic and Atmospheric Administration, AccuWeather and National Weather Service