The first in a series of storms that will make the pleasant weather of the past week seem a distant memory left the ground wet, the air cold and leaves swirling around most of the region before noon Wednesday.

By sunset, it was expected to be even wetter, colder and gustier, according to the National Weather Service — all of it from a pattern that the weather service said carries atmospheric river characteristics.

A couple of such patterns thrashed the Bay Area over the winter. This week’s pattern won’t be quite as intense, but it won’t pass through quietly, either. At least a half-inch of rain is expected to fall on the region from the three systems, and four inches may fall in the coastal ranges.

“This is probably going to be one of the weaker ones we’ve seen,” NWS meteorologist Brayden Murdock said Wednesday.

The Center for Western Weather and Water Extremes at UC San Diego forecast the atmospheric river to be weak, saying it rated as a 1 on a scale of 1 to 5.

The rain that fell before noon Wednesday came from what Murdock called “frontal showers” that preceded the main system. That left 24-hour rainfall totals at 11 a.m. of a half-inch at Saint Helena; three-tenths of an inch in Kentfield and San Rafael; about one-tenth of an inch in San Francisco and Ben Lomond; seven-hundredths of an inch in Richmond, and two-hundredths of an inch in Oakland. No measurable rain fell in San Jose.

The totals were expected to go up significantly by the time all three storm systems roll through the region.

The weather service said the first storm is expected to be gone by late Wednesday; the second one is forecast to arrive late today going into Friday and the final one is expected early Sunday and likely to last into Monday.

The initial system also will bring with it intense winds, according to the weather service. Gusts as high as 55 mph are expected in the higher elevations, and 20-30 mph gusts could blow steadily in the lower ones. The weather service issued a wind advisory from 8 a.m. to 8 p.m. on Wednesday.

Also expected on tap will be thunder and lightning. The weather service said Wednesday’s storm could light up the sky as far north as Santa Rosa and as far south as King City in Monterey County.

“The big thing with these thunderstorm chances is that they’re going to develop out over the (ocean),” Murdock said. “They’re going to start there and move inland, so we’ll be able to see them coming.”

Temperatures are expected to be cold as the storms move through. Daytime highs are not expected to exceed the high 50s until Saturday. Overnight lows are expected to dip into the low 40s in most of the region and into the high 30s in the most inland places.

“These subsequent systems are really not looking as strong as the first one,” Murdock said.