November through March is typically the rainy season for California.  These five months normally provide most of the yearly water supply for the state.  Dry winters can lead to droughts.  California just came out of a five year mega-drought in 2017, thanks to one of the wettest winters on record.  Currently, most of the state's reservoir levels are actually above historical average for this time of year.  But in order for those levels to remain high, winter rain is needed.  After some healthy rains at the beginning of the season, most of December was dry.  High pressure systems blocked Pacific moisture from coming into California.  It appears in the short term, the high pressure has weakened, allowing rain to arrive. There was rain in northern California on Wednesday ahead of a frontal system.  This trend will continue on Thursday.  Scattered showers will be mainly to the north of San Francisco. By Friday morning, the front will move inland, bringing more rain to the northern portion of the state. Even by Friday evening, the rain will stay behind the front, in northern California.  Very little rain is expected to reach southern California.  But this is actually pretty normal as far as weather patterns are concerned.  And that's a big reason why many reservoirs are located in the northern part of the state. In fact, 80% of southern California's drinking water, comes from reservoirs in the northern part of the state.  So moisture that falls in northern California, is a huge benefit for all locations in the state.  Rain is in the forecast through Saturday morning east of San Francisco and south of Sacramento.  There could even be a few inches of snow in the Sierra Nevada mountains. Storm totals could produce up to an inch of rain in areas shaded in green.  Areas in the orange and yellow shading could see between one and three inches of rain.  Reservoirs around the Chico and Redding areas, such as Shasta Lake, are included in this region. Most of the rain will be over, just in time for a great weekend.  Redding will be sunny, dry, and cool for the weekend.  Looking ahead, there could be another round of soaking rain next Tuesday. San Francisco is also showing great weather for the weekend and Monday.  And like Redding, more rain could be moving in by Tuesday. For Weather Nation:  Meteorologist Matt Monroe