LOS ANGELES — A powerful Pacific storm setup could bring heavy rain and thunderstorms to Southern California and parts of the West from Halloween through early November. Forecast models show a strong jet stream curving around an offshore low and aiming right at the coast. That setup could open the door for an atmospheric river. The period to watch runs from October 31 through November 5.
Offshore Low Spins West of California
The European model shows a strong area of low pressure sitting off the Southern California coast early on Sunday, November 1. The low is located west of Los Angeles over the Pacific Ocean. Its counterclockwise spin is pulling moisture and energy toward the coast.
Storms like this can wander slowly off the coast before moving inland. That slow movement could allow rain to fall over the same areas for a long time. It also gives the storm more time to pull in deep moisture.
Strong Jet Streak Aims at Southern California
High above the ground, at about 30,000 feet, very fast winds are shown racing around the low. This jet streak is aimed toward Los Angeles, San Diego, and the Inland Empire. Fast winds aloft help lift air upward, which can make rain and storms stronger.
When this kind of lift combines with deep moisture, rain bands can become intense. Some storms could also turn into thunderstorms with lightning and heavy downpours. That raises the risk of flash flooding in some areas.
Atmospheric River Possible
An atmospheric river is a long, narrow band of moisture that flows from the tropics toward land. When one reaches California, it can bring heavy rain at lower elevations and snow in the mountains. This setup shows some signs of that kind of pattern…