The National Weather Service is expecting rain and possible thunderstorms in the North Bay for the next couple of days. Forecasters expect a combined half inch to one-and-a-half inches of rain to fall in Sonoma and Napa Counties today and tomorrow. It would boost the rain total for March, which is traditionally the fourth-wettest month of the year. Charles M. Schulz-Sonoma County Airport has recorded two-and-a-fourth inches of rain so far this month.