High pressure has squished the marine layer so that the interior valleys get no help from it, as a result temps have again been in the upper 90s for most inland again today. But near the coast we have our microclimate coming out to play where temps are more than 30 degrees cooler during the peak heat of the day.
Marine clouds look to expand at beaches and get stubborn to clear.
Today it lingered around the Southcoast beaches, models show it lingering at Central Coast beaches by later Wednesday-Friday. I think the question is, does it happen sooner than that? We already have the moderating temperature from the marine layer at beaches and coastal valleys (which is not always a cloud deck). When this deck forms it looks low and dense which could mean some marine drizzle and possibly visibility advisories.
I think Wednesday and Thursday will be very hot inland as the ridge in the upper atmosphere remains, but coastal valleys will be mild and beaches likely cool with the marine clouds.
The entire area will cool Friday thru the weekend when an upper low currently merges with a trough swinging into the Pac NW. This will deepen the marine influence and allow cool air to get into the interior valleys.
The trough-upper low combo could also provide enough lift for some spotty showers near the coast. It has shown up on several model runs. A better chance north of here but the chances here are not 0% Friday night into Saturday. If it rains it'll be hundredths of an inch and the best chance should be near the coast.
There is actually a second little wave later Monday-Tuesday that could again even produce light showers, but that's missing the main point that temps will drop back to below average into the from the weekend into the middle of next week at least.