Tour of California, Rose Parade and rain make for a busy, wet weekend ahead for Santa Rosa

As Santa Rosa prepares to host one of the busiest and most logistically complex events in its history Saturday - two professional bicycle races with a popular parade thrown in for good measure - organizers are bracing for yet another complicating factor: rain.

Forecasts show a risk of showers in the morning with the chances of rain increasing in the afternoon, around the time the seventh stage of the men’s Tour of California will be finishing downtown.

The prediction complicates but does not dampen enthusiasm for a day-long event that despite the weather is still expected to bring throngs of residents and tourists downtown.

“Between two professional bicycle races and the Rose Parade, we expect this is going to be the largest community event in Santa Rosa history,” said David Guhin, co-chairman of the local organizing committee.

The possibility of rain, while far from a certainty three days before the event, Guhin noted, could “add a layer of complexity from a race organizer standpoint” but was not expected to have a significant impact on attendance.

“Ideally, we would want perfect weather for our community and the crowds,” Guhin said. “But in years past, when it has rained, the crowds have come out in force, and it was amazing.”

When Amgen officials moved the race from February to May in 2010, they did so largely to avoid the storms that had soaked riders in previous years.

How any rain affects the tightly choreographed day remains to be seen.

A low-pressure system currently in Canada is expected to slide south through the Pacific Northwest and into Northern California on Friday evening, bringing with it lower temperatures and the risk of showers, according to Steve Anderson, a forecaster with the National Weather Service. Daytime highs in the area, now in the 80s, will drop into the 60s Saturday, he said.

The system will dive below and become detached from the jet stream, meaning it will “just kind of wander around aimless like a drunk in the street” for a couple days, Anderson said.

“It’s not going to race through in a matter of hours. It’s going to be here Friday through Sunday, maybe parts of Monday,” he said. It’s difficult to say precisely yet when the rain will begin or how steady it will be, but best estimates are that it will be ‘intermittent’ throughout Saturday, with about a tenth of an inch of total precipitation,” Anderson said.

“A tenth of an inch isn’t a lot, but it’s enough if you’re riding your bike to make it unpleasant and the roads slick and hazardous,” he said.

The first significant signs of activity from the public’s perspective will be the north-south closure of Mendocino Avenue at Old Courthouse Square at Third Street Friday morning. The closures of downtown streets will continue progressively through the day and overnight, Guhin said.

You can reach Staff Writer Kevin McCallum at 521-5207 or kevin.mccallum@pressdemocrat.com.