SAN FRANCISCO (CBS SF) — A winter-like storm front began sliding toward the San Francisco Bay from the Pacific Northwest Monday, threatening to dump as much as an inch of rain by midweek.

Carolina Walbrun, a meteorologist with the National Weather Service, said a stormy week was in store for the Bay Area beginning early Wednesday.

“What’s unusual is the model for these storms, and the timing and the strength of these storms,” Walbrun said.

The weather service predicted that light rain may begin in the North Bay on Tuesday night.

“Rainfall is then expected to become more widespread and increase in intensity on Wednesday, and especially Wednesday night,” forecasters said. “The heaviest rain will occur on Wednesday night and early Thursday when moderate to locally heavy rain rates are possible. Rain is then expected to change over to showers on Thursday.”

Rainfall totals during the second half of this week were forecast to range from a half inch to an inch across most of our area, with isolated amounts up to 1.5 inches or more possible.

Another storm front is expected to roll into the region in time for the weekend. Rain totals were forecast to be another 1/2 inch or more.

The weather service said if the “active weather pattern” persists on into next week as currently forecast, rainfall totals could become very impressive for this time of the year.

The weather service said rainfall totals through the middle of next week range from 2 to 2.5 inches across our area.

“While 10-day rainfall totals of this magnitude would not be at all unusual during the winter months, they would definitely be unusual for mid May, the weather service said.

Winds could also be a factor, especially late Wednesday and Wednesday night when gusty southerly winds are are expected to develop.