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Late-Season California Rainstorm

April 25, 2012; 12:43 PM ET

Two storms will combine to bring late-season rain to California Wednesday night into part of Thursday. This continues the wet weather pattern that started back in the middle of March.

The two storms can be seen nicely on satellite pictures.

The southern storm is out west-southwest from San Diego and is moving east with a nice area of rain offshore. The northern storm is a well-developed cold front from the western Washington states south to off the northern California coast. That front is moving southeast.

The southern storm has tapped a very rich moisture source from the subtropics. As it continues east it will act on this warm, moist air and produce a decent period of rain and even a thunderstorm in spots tonight into tomorrow morning. This satellite pictures shows the amount of precipitable water in air. Notice the red plume extending north to Southern California.

It is because of this moisture and the low moving in that I am expected 0.50 to 1 inch of rainfall from the Los Angeles Basin on south and from the mountains on west. In the deserts, it will also rain some but amounts will be in the range from 0.10 to 0.25 of an inch. The greatest amount of rain will probably fall in a five- to seven-hour period. Showers will linger into tomorrow morning before mostly ending during the afternoon.

The northern branch storm will also spread rain in across northern and central California tonight into part of tomorrow. Also 0.50 to 1 inch of rain is likely in northern and north-central areas and along the Central Coast. In the San Joaquin Valley expect more like 0.25 to 0.50 of an inch on average with more in the Sierra foothills.

Snow will not be a big issue with either of these storms. Snow levels will be 8,000 feet or a little higher for a time tonight and only drop to near 7,000 feet late tonight or tomorrow morning in the south while staying at or slightly above 7,500 feet in the Sierra.

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or


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Ken Clark
Ken Clark's Western U.S. weather blog tackles daily weather events with commentary from one of the most experienced and trusted Western U.S. weather experts.