Wednesday is the last sunny and mild day before we transition to cooler weather

Our upper low is drifting past Point Conception to the east, allowing a pop-up ridge of high pressure to move in to Southwest California on Wednesday. It will allow temperatures to stay nice and mild. Highs will be in the 60s and up to 70 degrees in a couple coastal valleys. Lows will be chilly in the 30s to 40s.

Patchy low clouds could still develop Wednesday morning as offshore flow will be very weak. By the afternoon, onshore winds will return. As such, there will be a much more extensive marine layer at night. Also, our brief ridge of high pressure will start to exit east overnight.

We may wake up to patchy drizzle out of the marine layer on Thursday morning. Skies will be mostly to partly sunny during the day. We will have breezy west to southwesterly winds in the afternoon. Temperatures will begin to drop ahead of another system, and struggle to reach 60 degrees by the weekend.

A large and cold trough will sweep through the West Coast Friday and Saturday. It will bring a chance of rain to San Luis Obispo and Santa Barbara Counties by Friday morning, with chances extending into Ventura County by the afternoon or evening. Rain will continue into Saturday before tapering off in the evening. Estimates show a 0.33 to 1.5 inches of rain, with the highest totals in the mountains.

Snow levels will drop from 6,000 feet Friday night to 3,000 feet late Saturday night or early Sunday morning. We expect 8 to 16 inches above 7,000 feet, 4 to 8 inches above 5,500 feet, and light accumulations above 3,000. Frost and freeze warnings are possible in wind-sheltered valleys.

Winds will turn northwesterly on Sunday following the storm, in particular affecting southwest Santa Barbara County. Temperatures will warm back into the 60s by early next week.