A series of storms is expected to bring rain, mountain snow, and colder temperatures to California beginning Friday, as forecasters monitor atmospheric river activity along the West Coast.

The National Weather Service in Hanford said precipitation would begin Friday morning and continue into the evening, with rain and snow lingering over the Sierra Nevada into early Saturday.

The forecast follows an outlook from UC San Diego’s Center for Western Weather and Water Extremes identifying elevated chances of atmospheric river activity reaching Northern California through Saturday.

For Fresno and areas farther north in the San Joaquin Valley, forecasters put the chance of at least a quarter-inch of rain at 60% to 70%. Areas farther south generally could get about a tenth of an inch.

A winter storm warning runs from 10 a.m. Friday through 4 a.m. Tuesday for portions of the Sierra, with total snowfall reaching 18 inches above 6,000 feet.

Saturday should be relatively dry before another storm arrives late Sunday, bringing additional rain and mountain snow through Monday night.

A third system is expected Wednesday into Thursday. Temperatures will fall sharply, with daytime highs around 10 degrees below average across much of the region during the coming week.

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