Putah Creek in Yolo County. Forecasters advise keeping an eye on streams for potential flooding. (Photo: Craig Miller)

All aboard the Pineapple Express!

Forecasters are telling us to prepare for high winds and heavy rainfall over the next several days. A line of Pacific storms is set to sweep through Northern California starting tonight. By the time it moves through on Sunday, it could go down as a major weather event.

There might not be much in this for skiers–or the Sierra snowpack, which ended last season on the thin side.

“Snow won’t be a major concern,” says Johnnie Powell, a forecaster for the National Weather Service in Sacramento. “Snow levels are going to be above 7,000 feet, so it’s a very warm storm in nature.” (Snow elevations could start out at the 5,000-6,000-foot level but then “quickly rise” to 7,000 or higher.)

And it’s a wet one. Powell says the stage is set for what forecasters call the “Pineapple Express,” a series of systems that pick up moisture from the tropics and dump it on our doorstep. In its most extreme form, meteorologists refer to these as “atmospheric rivers.” Some lower elevations could see seven inches of rain through Sunday, with as much as 18 inches possible in the mountains — that’s more than a foot of rain, spaced out mercifully over several days.

NOAA satellite image shows water vapor (white areas) swirling toward California.

“The biggest concern of all is where we had the fires during the summer,” says Powell. “They may have some debris flooding in some areas near the fires, because they just don’t have the right soil [conditions].”

California’s Emergency Management Agency has issued a warning, saying, “local power outages are possible as a result of downed trees from gusting winds. Small stream flooding is also likely with weir overflow and runoff.” Weirs are gates that separate rivers from designated flood bypasses. The Weather Service says some reaches of the northern Sacramento River could overflow into bypasses during this event, which will arrive in waves.

CalEMA went on to warn that “it’s critical that the public take a personal interest in preparing for this storm, and the storms that will follow throughout the winter season.”

It’s still unclear what sort of wet season we’ll have overall. The usual signals from the Pacific Ocean are mixed. But these storms will help key reservoirs, many of which are below normal levels for this time of year.

Tips for storm preparedness are posted at the CalEMA website.

First Major N. Calif. Storm Sequence of the Season Looks Like a Gully Washer 28 November,2012Craig Miller


Craig Miller

Craig is KQED’s science editor, specializing in weather, climate, water & energy issues, with a little seismology thrown in just to shake things up. Prior to his current position, he launched and led the station’s award-winning multimedia project, Climate Watch. Craig is also an accomplished writer/producer of television documentaries, with a focus on natural resource issues.

Sponsored by

Become a KQED sponsor