We are still several days from moderate rains but light showers could start as early as Saturday. More on that later after we tackle the short term forecast.
We already have a mix of low clouds and some haze at the coastline and near coastal valleys, those low clouds will continue to push into the coastal valleys this evening and linger until Friday morning when the clouds should retreat to the beaches, but at the beaches they could linger in a patchy way all day.
An approaching trough and cold front could cause mist or drizzle as early as late Friday night into the wee hours of Saturday morning, but the actual cold front passage looks to begin around sunrise. The front essentially stalls and dissipates over the area into Saturday evening. The chances for showers early Saturday look better in SLO county and the western portion of Santa Barbara county.
Late Saturday looks different, the SW push of moisture begins and late Saturday night into Sunday morning the Southcoast is in the action as more showers push north across the area into Sunday afternoon.
A large low off the coast Sunday will likely move into the state Monday and Tuesday and slowly drag thru the state into Wednesday. Looks like several days of off and on rain. There is still high confidence in moderate rainfall.
1-4" of rain looks like a good ballpark to work with at this point. The low looks to tap into sub-tropical moisture. We'll have to watch the rain rates carefully. 1-4" of rain spread over 3-4 days can be OK but if it gets concentrated to a 24 hour time frame then flooding issues could be something to consider. The system next week will also have strong S-SW wind