3:45 p.m.The National Weather Service has issued an urban and small stream flood advisory for Napa, Sonoma and Marin counties from 4 a.m. to 4 p.m. Friday. The flood advisory means flooding of urban areas and some small streams or creeks is expected by the weather service for some of the area.

“We are going to have the bulk of the rain in Napa County on Friday between 4 a.m. to 4 p.m.,” Napa County spokeswoman Mary Jean McLaughlin said. “We had a conference call with the National Weather Service this morning and they said the heaviest part of the storm will hit the Santa Cruz area, not us.”

Residents can expect as much as three to four inches of the wet stuff, starting early morning and tapering off by late afternoon.

After that? Don’t put away the umbrellas.

An unstable air mass is expected to waltz in Saturday, brining much colder temperatures, showers and thunderstorms, McLaughlin said. “But the heavy rains will have passed through.”

Snow level is expected to drop to 2,000 feet, meaning there will be snow on Mount St. Helena.

And don’t forget the wind.

The National Weather Service has issued a high wind advisory for Friday. The coastal region is expected to take the brunt of the strong winds, but Napa County will also get a pretty good dose, McLaughlin said. “Strong winds bring a high potential for power outages with tree branches into power wires and down power lines.”