California Weather Forecast: ‘Pineapple Express’ to Bring Heavy Rains

An atmospheric river of moisture, stretching over 3,000 miles past Hawaii, was streaming into California on Wednesday.

Forecasters have warned California residents that unsettled weather through Thursday is likely to bring heavy rains, strong winds and mountain snow as the storm moves down along the West Coast. A similar storm will threaten the region early next week.

When the tail end of an atmospheric river stretches back toward Hawaii, like this one, it is often called a “Pineapple Express.”

The rainfall began during the Wednesday morning commute in some areas and continued during the afternoon farther south down the coast.

Flooding concerns, like overwhelmed storm drains that can lead to road closures, will be widespread, and the heavy rain that falls could create localized areas of flash flooding, with urban areas, roads, small streams and burn scars the most vulnerable, forecasters said.

The storm is predicted to be a moderate atmospheric river, and nowhere near the strength of an “Ark storm,” as has been making the rounds on social media in the past few days. Nor is the forecast likely to be anywhere near as severe as the series of back-to-back storms last winter that led to widespread flooding and historic amounts of snow in the region.

This midweek storm, while still having the potential to produce flash flooding and heavy mountain snow, is expected to move quickly, which would reduce the amount of rain that falls over any one location.

A foot or more of snow is forecast over parts of Northern and Central California. The Sierra Nevada will get heavy snow from late Wednesday morning into Thursday.

Farther north, heavy rainfall through Wednesday may lead to increased threats of landslides in Western Washington, forecasters warned in a special weather statement. The consistent rainfall over the last few days, and with more in the forecast, puts extra pressure on soil instability. At least two landslides have been reported thus far in Western Washington, including one in a Seattle neighborhood.

Here’s what to know about the timing.

• Wednesday: A robust plume of moisture will move over California, with the heaviest rain falling over the northern Bay Area and the Sacramento area Wednesday afternoon before drifting farther south in the evening and overnight.

The next atmospheric river could be more robust than this one.

It is “increasingly likely” that another strong weather system and possibly a “significant atmospheric river event” will affect California late this weekend into early next week, forecasters with the Weather Prediction Center said.

Despite many possible outcomes, the atmospheric river arriving Sunday into Monday has the potential to produce greater low-elevation rain and mountain snow totals than this week’s event.

A worst-case scenario would be if the storm system stalls off the coast, which could prolong the rain and snow. This scenario would bring a high risk of flooding and heavy mountain snow, forecasters in Los Angeles warned.

Derrick Bryson Taylor contributed reporting.