437 FXUS66 KSGX 211009 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 309 AM PDT Fri Jun 21 2019 .SYNOPSIS... A low pressure system over the western states will maintain stronger onshore flow today which will spread cooling inland and continue periods of stronger and gusty southwest to west winds in the mountains and deserts. The marine layer will deepen with patchy drizzle and a chance of light showers into this morning. For Saturday through Monday, the low pressure system will weaken and move east. There will be a warming trend for inland areas, winds in the mountains and deserts will weaken, and the marine layer will become a little less deep. Tuesday and Wednesday will be a little cooler, then slow warming into next weekend. Summer begins at 854 AM PDT today. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... A large low pressure system will remain across the western states today. This will maintain stronger onshore flow into this evening with periods of strong and gusty southwest to west winds in the mountains and deserts. The marine layer has deepened to around 4000 feet with coastal low clouds extending inland onto the lower coastal mountain slopes. There has been drizzle overnight with the greatest concentration of light measurable amounts in coastal areas with a lot less in the valleys. There have also been some scattered light showers, mostly in the coastal areas of San Diego County and the adjacent coastal waters. These scattered light shower will continue for coastal areas through around 6 AM, then may move inland into portions of the San Diego County valleys through 8 AM and dissipate. High temperatures for the inland valleys, mountains, and deserts will be around 5 to 10 degrees cooler today than on Thursday. That's 15 to 20 degrees below average for the valleys and mountains and 10 to 15 degrees below average in the deserts. The west winds in the mountains and deserts will subside tonight with locally gusty north winds to around 35 mph in portions of the San Bernardino County mountains for Saturday morning. North to northeast flow aloft will bring faster and greater clearing of the low clouds west of the mountains on Saturday. It may also delay the return on Saturday evening. There will be a warming trend for Saturday through Monday, but with high temperatures for the mountains and deserts still a few degrees below average. For the middle to latter part of next week, there will be a large, closed low pressure system over the eastern Pacific, centered just off or near the Pacific Northwest coast. High pressure aloft will be to the southeast extending from central Baja into New Mexico. Southern California will be in between with continued onshore flow and southwest flow aloft. There will be minor day to day difference with current guidance a few degrees cooler for Tuesday and Wednesday, then a few degrees warming for Thursday and Friday. Night and morning coastal low clouds will continue to extend inland into portions of the valleys. && .AVIATION... 210925Z...Coast/Valleys...Stratus with bases 1500-2500 ft MSL and tops to 4500 ft will continue along and west of the mountains this morning. Local vis 2-4 SM in DZ/-RA through about 18Z. Stratus slowly clearing inland 18-20Z, with coastal areas remaining BKN-OVC through the day. Low clouds will fill in west of the mountains again tonight with similar bases and tops. Mountains/Deserts...Coastal slopes obscured in clouds/fog through about 19Z and again after 06Z this evening. West winds with surface gusts of 30-45 kt over the mountain crests, desert mountain slopes, and below passes will gradually weaken through 19Z. Winds will strengthen again this afternoon and evening with gusts 35-45 kt, weakening late tonight. Areas of strong UDDFS and rotors possible over and east of the mountains. && .MARINE... No hazardous marine conditions are expected through Tuesday. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory until 9 PM PDT this evening for Apple and Lucerne Valleys-Coachella Valley-Riverside County Mountains-San Bernardino County Mountains-San Diego County Deserts-San Diego County Mountains-San Gorgonio Pass Near Banning. PZ...NONE. && $$ PUBLIC...17 AVIATION/MARINE...SS