The headline for this story is about a brief shower or thunderstorm potential early Sunday morning, it is not really the emphasis of the forecast which continues to be pretty mild for most outside of the interior valleys. But folks in the interior valleys are already experiencing cooler weather than Thursday when highs briefly topped 100 degrees.
The shower/thunderstorm potential comes as the easterly push of the summer monsoon peaks early Sunday, prior to that the activity stays too far east (though the Sierra and parts of eastern and southern CA do have higher potential).
After the Sunday morning potential, it looks like upper atmospheric steering winds shift from easterly to SW by later Sunday and any further monsoon activity appears unlikely.
Other than that, the night and morning marine presence will still be significant. The mid and upper-level clouds could cause the cloud deck to not be as firm and consistent but regardless the cooling impact of marine-influenced air will be present. So beaches stay in the 60s over the weekend with the coastal valleys in the 70s and interior temps in the 80s and 90s.
There really isn’t a huge trend other than the interior cool-down which really already took place today, we look to stay fairly level with perhaps a slight uptick in temperatures as we move into the midpoint of next week.