Get ready, Oregon: A strong jet stream that's already picking up moisture from a western Pacific Ocean typhoon could bring the first atmospheric river -- more commonly called the Pineapple Express -- to the Pacific Northwest this weekend.



Water vapor satellite images show that tropical moisture from Typhoon Phanfone is being pulled into the jet stream and combining with a low pressure center in the Gulf of Alaska to create a weather system that could hit as early as Friday, said Will Ahue, a forecaster for the National Weather Service in Portland.



"The issue for us is timing,'' Ahue said. "The forecast models are having a bit of a hard time figuring out when and where" it will land.



While the models aren't predicting any flooding in western Oregon, the approaching system should bring significant rain to northwest Oregon and southwest Washington over the weekend.

That will end the rain-free October in Portland and tamp down the record- and record-tying high temperatures of this past weekend.

For the uninitiated, the Pineapple Express is notorious for causing floods, landslides and mudslides in Oregon and Washington.

"When you look at past occurrences of heavy rain over a multi-day period it almost always has this component of the Pineapple Express, or the atmospheric river," said Andy Bryant, a forecaster and hydrologist with the Northwest River Forecast Center in Portland.



When that typically deep subtropical moisture interacts with low pressure systems and gets caught up in the jet stream, it creates a long, undulating river of rain in the upper atmosphere.

When it makes landfall, the atmospheric river delivers loads of rain. The effect is enhanced when rain-laden clouds slam into the Coast Range, where steep hillsides squeeze even more moisture out of the clouds.



"The tricky thing for us is figuring out the details of that firehose ... specifically which areas will get the heaviest rainfall?" Bryant said.



It was the Pineapple Express that in November 1996 broke the one-day rainfall record for Oregon when 11.65 inches fell at Elk River Hatchery in Port Orford.

Ten years later, that record drowned under another Pineapple Express onslaught that dumped the all-time one day record rainfall for the state of 14.30 inches at Lees Camp east of Tillamook in the Oregon Coast Range.



That November, 11.92 inches of rain fell in Portland, making it the city's wettest November since record-keeping began at Portland International Airport in October 1940; the record still stands today.



Other significant Pineapple Express floods in northwest Oregon and southwest Washington:



* Dec. 19-25, 1964: A Pineapple Express, combined with heavy snow that melted rapidly, created widespread flooding. In Oregon, 17 people died, damage was $37 million.

* Feb. 5-9, 1996: Record-setting rains and snowmelt, including a Pineapple Express, created massive flooding. Damage estimates in Oregon and Washington were in excess of $100 million.

* Nov. 18-20, 1996: The official single wettest one-day record for Oregon up to that time, 11.65 inches, Five people died in Douglas County from flooding.

* January 2006: Gov. Ted Kulongoski declared a state of emergency in 24 of Oregon's 36 counties and asked federal disaster officials to help assess the millions of dollars in damage caused by four weeks of high winds and unrelenting rains.

* Nov. 6, 2006: Lees Camp near the Wilson River east of Tillamook received 14.30 inches of rain on Nov. 6. The rains flooded houses and businesses in Tillamook, undermined million-dollar homes on the coast and the Sandy River, and caused a major washout of Oregon 35 near Mount Hood.

* January 2012: President Obama declared a major disaster in 12 Oregon counties because of a severe winter storm that slammed the state with high winds, landslides and flooding rains that came into the state on an atmospheric river.

-- Stuart Tomlinson