A large ridge of high pressure is in place over The West but conditions will change between now and the end of the week.
A trough and a cold front pass to our north later Wednesday which will starts a temperature slide into the weekend. The changes will also likely be marked with some locally gusty winds, especially at higher elevations and passes and canyons but currently, no advisories are in place.
The second half of the week is interesting, at least meteorologically: An area of low pressure looks to wobble along the SoCal and AZ border, this could be enough to cause some instability for some isolated showers and thunderstorms across southern California but locally activity is not likely.
Another interesting element is that another ridge builds in but the Central Coast and SoCal will be under some upper-level NE flow if any of this couples down we could see offshore flow, but right now models still favor some mild temps.
Fall officially begins Wednesday afternoon with the equinox but meteorological fall is generally considered to be September, October and November.