088 FXUS66 KSGX 101642 AAA AFDSGX Area Forecast Discussion National Weather Service San Diego CA 940 AM PDT Wed Oct 10 2018 Updated marine, aviation, and beaches sections .SYNOPSIS... Cool weather will continue as low pressure dominates the West. Scattered light showers are possible tonight into Thursday. After some offshore flow and foothill winds Friday morning, moisture from the south will bring a chance of showers Saturday into Monday. Offshore flow continues next week and combines with higher pressure to bring a drying and warming trend after Monday. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Low clouds are gathering in much of the coastal basin, but a weak marine inversion and a batch of high clouds drifting overhead have disrupted the cloud factory. That has made the cloud coverage less than uniform. The marine layer is quite deep and will deepen today and tonight as a short wave low pressure trough zips through California. Light showers or drizzle are expected, but with little if any accumulation. Behind that wave, some offshore flow develops Thursday night and peaks Friday morning. Easterly winds will develop mainly in the foothills, and top gusts in the typically favorable spots could exceed 40 mph. Meanwhile, hundreds of miles to our south, Sergio will weaken and stagger into southern Baja and Sonora. He will serve up some moisture as a dying gift all over northwest Mexico. Back up north, a trough of low pressure develops over California and cuts off in the ocean to our west Friday and Saturday. It's not a strong cutoff low, but it grabs some of that moisture over Mexico and draws it into Southern California. A deeper, colder trough moves through the interior West, which brings in colder, heavier air and therefore high pressure, setting up an offshore pressure gradient over the Southwest. You knew it was coming as it does every fall: offshore flow and occasional Santa Ana episodes. We'll get some offshore breezes Sunday into Monday, but thankfully they don't appear to be very strong and we have too much moisture in the air for it to be scary dry and a serious threat for fire growth. In fact, that cutoff low moves very slowly to our south and continues to draw that tropical moisture wrapping around into our region for a couple days. Despite the drying influence of offshore flow, the chance of showers is forecast to persist into Monday, and it could go beyond that. With the deepest moisture to our southeast, the chances of showers drop off the farther north and west you go (i.e., no real chance in the high desert). By next Tuesday or Wednesday the low scoots east and should take the moisture/clouds with it. Gotta say model agreement during this highly amplified and variable weather pattern is quite impressive right now. It will be interesting to see if they gain consistency with the current solution, and resulting forecast. && .AVIATION... 101530Z...Coasts/Valleys/Coastal Mountain Slopes...Low clouds currently in western Riverside County will clear out by 17Z. SCT clouds expected in the coastal valleys and immediate coastline for the majority of the afternoon. Low clouds spreading into the lower coastal slopes overnight with tops rising to around 4500-5000 ft MSL by Thu morning. Redevelopment along the coast around 12Z Thursday with bases near 2500 ft MSL. DZ/ISO -SHRA possible along and west of the mountains Wednesday night with vis lowering to 3-5 SM and CIGS 1000-1500 ft MSL in -SHRA. Desert Mountain Slopes/Deserts...SCT-BKN clouds AOA 20000 ft MSL and unrestricted vis through Thu morning. && .MARINE... No hazardous marine weather through Friday. A low pressure system will bring a slight chance of showers beginning early Saturday. && .BEACHES... South swells from 200-210 degrees generated by Tropical Storm Sergio will build through Friday. This will bring increasing surf, peaking late Thursday through Friday at around 5-8 ft with higher sets. The swell and surf will decrease late Friday and Saturday. Minor coastal flooding is possible during morning high tides, which peak around 6 ft. There will be strong rip and longshore currents. For more details, see the Beach Hazards Statement and the Surf Zone Forecast. && .SKYWARN... Skywarn activation is not requested. However weather spotters are encouraged to report significant weather conditions. && .SGX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement through Friday afternoon for Orange County Coastal Areas-San Diego County Coastal Areas. PZ...NONE. && $$ PUBLIC...MM AVIATION/MARINE/BEACHES...ADR