Southwest California area forecast discussion...updated National Weather Service Los Angeles/Oxnard California 500 PM PDT Tuesday may 21 2013 ..updated aviation discussion... Synopsis... A cooling trend that began for most areas today will continue through the weekend along with an increase in night through morning low clouds and fog. Breezy conditions are expected along the central coast...southern Santa Barbara County...Interstate 5 corridor...and the Antelope Valley. && Short term (today-fri)...a strong onshore push today brought cooling to most areas except some of the mountains and Antelope Valley. This will continue and spread further inland through the weekend as a persistent trough sets up along the West Coast. Slight deepening of the trough is expected Wednesday and Thu, and this combined with a strengthening eddy circulation (thanks to increasing outer water winds) will possibly be enough to generate some drizzle during the overnight hours across Ventura and la counties. That increase in northwest flow around pt Conception and through the Santa Ynez range will likely keep low clouds out of southern sba County the next few days with warmer temperatures there. Winds will be close to or locally exceeding advisory criteria for southern sba County, the i5 corridor and the Antelope Valley starting late Wednesday. If the models are to be believed, the trough briefly lifts on Friday, resulting in a very slight warming trend Friday, maybe a few degrees at most, and earlier marine layer clearing. Long term (sat-tue)...trough deepens again over the Holiday weekend. Decreasing northwest flow should allow the low clouds to spread up the coast through slo County and we may see areas of drizzle again each morning through Monday. Limited coastal clearing and clouds may linger into early afternoon for some of the valleys. Daytime temperatures expected to run 2-4 degrees below normal. The trough is expected to shift east Tuesday for a warming trend going into the middle of next week. && Aviation...21/2355z. Satellite imagery showing low clouds surging quickly into the la County coastal areas late this afternoon...including klax. Clearing being observed to the northwest of la County. Lower confidence in low clouds returning to coastal areas north of Point Conception...with higher probability of ceilings across la County coast/valleys tonight. Appears that eddy will be strong enough to bring low clouds back into koxr early Wednesday morning. Eddy circulation expected to maintain ceilings in MVFR category for the most part...with the exception of a 30 percent chance of IFR conditions in the valleys (including kbur and kvny). Gusty winds across the passes and canyons of sba County this evening and somewhat stronger tomorrow evening...bringing a good chance of low level wind shear both evenings. Also...gusty west to northwest winds will be affecting ksmx...ksbp...kpmd...and kwjf through period. Klax...low clouds surging in quickly as of 00z with MVFR ceilings already observed. Current thinking is that low clouds will likely linger for the night...but there is a 30 percent chance that low clouds could scour out for a few hours later this evening before returning. Ceilings generally expected to remain in MVFR category. Kbur...fairly high confidence that low clouds will return overnight into Wednesday morning. Leaning towards MVFR category...but a 30 percent chance of IFR conditions. && Lox watches/warnings/advisories... Gale Warning (see laxmwwlox). Small Craft Advisory (see laxmwwlox). High rip current risk (see laxsrflox). && $$ Public...mw aviation...gomberg synopsis...kj Www.Weather.Gov/losangeles