Anticipated rain will bring end to Bay Area’s dry pattern

After weeks of mostly dry weather, a change to the Bay Area’s weather pattern already was underway by Tuesday morning, and the result is expected be significant periods of rain in the days ahead.

“We’ve got a rain pattern,” National Weather Service meteorologist Brayden Murdock said. “So that’s a switch.”

The pattern change began Monday when the barometric pressure surrounding the region started to fall gradually. That low pressure is coming from the southwest and the air is flowing north, the opposite of many winter low-pressure systems that dip in from the Pacific Northwest.

As a result, light but steady rain is expected to start in Monterey County and the Central Coast late Tuesday morning. The rain is expected to reach the region closer to San Francisco sometime Tuesday night, Murdock said.

According to Murdock, the central coast and areas in the Santa Cruz Mountains and Big Sur may receive as much as 2½ inches during this initial burst. The way the air is churning around the low pressure also is expected to create some heavy winds in that area, according to the weather service. A wind advisory begins for Monterey and San Benito counties at 4 p.m. Tuesday and will be in effect through 4 p.m. Wednesday.

The rest of the region is expected to get anywhere between a half-inch and three-quarters of an inch of rain in the early part of the week. Murdock said the anticipated rain is expected to be “easy-going, with a few waves where the rain becomes moderately heavy. It’s not going to be widespread hard raining.”

That will change come the weekend, he said. By then, a heavier system is expected, with low pressure complemented by a cold front. The weather service remains unsure when that surge will move through the region or how much rain will fall. But Murdock said it is supposed to be a more intense storm than what is arriving Tuesday.

“In the last 24 hours, the biggest change is that we think the weekend stuff has been pushed back,” Murdock said. “Right now, we think it will be Saturday evening. Once we start seeing that rain, the chances are good that it will extend into next week.”

In the Sierra Nevada, the systems will translate to snow. Rain showers are expected to change into snow showers late Tuesday into Wednesday, with winds becoming increasingly heavy near the higher elevations. A heavier winter storm is then expected to start Saturday and move into Sunday.