409 FXUS66 KSGX 220915 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 215 AM PDT Mon Oct 22 2018 .SYNOPSIS... A trough of low pressure moving slowly inland across Southern California will bring cooler weather through Tuesday. A deeper marine layer will bring more night and morning low clouds to the coast and western valleys. The weather will turn much warmer Wednesday through Friday as high pressure over the eastern Pacific builds over central California. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds have organized and uniform coverage is marching inland this morning. It looks like clouds and fog might barely sneak into the Inland Empire through its western and southern portals before sunrise. Patchy fog with low visibility could occur anywhere between 1,200 to 1,800 feet elevation. Meanwhile, there are thunderstorms(!) in the desert of San Bernardino County, yes even this time of the morning. A weak upper low moving through Southern California can explain the storms and also the marine layer development. We don't expect the moisture or instability to be sufficient for storms in our region today, but you'll see some cumulus clouds over the interior, especially in the mountains. And that looks to be the case through Tuesday and Wednesday. The marine layer and coastal cloud coverage will be similar through Tuesday. There will be some high clouds from time to time as well. As the low moves on, the higher pressure will tamp down the marine layer a step for Wednesday and Thursday for less cloud coverage in time and space. There's also a touch of offshore flow each morning; after all we are in October. A high pressure ridge over the eastern Pacific Ocean noses boldly into California as we head into the weekend. A little more offshore flow will develop to bring areas of offshore breezes. The combination of ridging aloft and the offshore flow at the surface will boost temperatures quite a bit for Thursday through Saturday. Right now it appears the warmth peaks Friday, particularly for the coastal basin. As the offshore flow weakens over the weekend, the warmth will migrate into mountains and deserts. High temps on Friday will feature some 90s. The upper ridge weakens slightly next week with some form of western trough coupled with a baggy weak trough to our south. This would probably bring us more low and high clouds and slightly cooler weather. && .AVIATION... 220850Z...Coast/Valleys...Stratus with bases 1100-1500 ft MSL continuing along the coast and local 15-20 mi inland this morning. Local vis 3-5 SM in BR/HZ along inland extent of low clouds. Clearing to the coast will occur 16-19Z, though beaches may remain locally BKN through the afternoon. Stratus will spread back into the coastal areas around 23/02Z and 15-20 mi inland overnight. Bases will remain near 1000-1500 ft MSL. Mountains/Deserts...FEW-SCT mid and high clouds and unrestricted vis through Tuesday morning. && .MARINE... No hazardous marine weather is expected through Friday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MM AVIATION/MARINE...SS |