Northern California, Oregon to be Hit With Heavy Rain and Flooding Into Saturday

By Meghan Mussoline, Meteorologist

February 6,2015; 10:09PM,EST

 

 

Heavy rain will inundate coastal Oregon and northern California into early next week, threatening serious flash flooding, mudslides and travel delays and cancellations.
A Pineapple Express will help to fuel the heavy rain as the first of two major storms plows into the Pacific coast through Saturday.
The heaviest rain from the first storm will soak Northern California through Friday night.
"A Pineapple Express is a continuous surge of tropical moisture extending from near Hawaii all the way into a West Coast storm," AccuWeather.com Senior Meteorologist Bernie Rayno said.
This pattern can significantly enhance rainfall and threats such as flooding. Recent burn scar areas in California will be especially vulnerable to flooding and debris flows, since rain water cannot penetrate scorched ground.


Widespread rainfall amounts of 2-3 inches are expected in western Oregon and northern California, including in the Bay Area. In far northern California, amounts will exceed 6 inches in some communities through Saturday.
Lengthy flight delays and cancellations are possible at San Francisco International Airport on Friday due to low clouds and excessive rainfall associated with the storm.
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Motorists may face travel problems on the ground as rain mixes with oil buildup on roadways to create slick conditions.

During Saturday into Saturday night, the rain will taper to showers. However, runoff will continue to cause small streams to run high.
A second storm will arrive along the West Coast Sunday into Monday, unleashing another round of heavy rain and most likely another dose of flash flooding, mudslides and travel disruptions.
The rounds of rain follow after an extremely dry January for many locations.
"This is the first significant rain [for Northern California] since the middle of December," Clark said.
January 2015 went down in the record books as the driest January on record for San Francisco with no rain recorded.
The second longest period of dry weather on record has ended at 43 days in San Francisco as of 9 a.m. PST on Friday. The longest period with no measurable rain on record was 60 days spanning Nov. 17, 1876, to Jan. 15, 1877. Records at San Francisco date back to 1849.
Meanwhile, mountain snowpack is an important resource for filling reservoirs and water supply for drought-stricken California. It is crucial to look at snowpack when analyzing the potential impact of storms on the ongoing drought. However, mountain snow is not likely with the upcoming storms, Clark said.
"Snow levels, because of the warm subtropical flow, will be very high, above 8,000 feet most of the time," Clark said. "Therefore, while the rains are welcomed, though too much in some places is not good either, these storms will be no help in putting down a snowpack."
Keep checking back with AccuWeather.com for updates on the Pineapple Express setting up and any potentially life-threatening flooding that may result.