980 FXUS66 KSGX 092034 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 134 PM PDT Tue Oct 9 2018 .SYNOPSIS... Onshore flow with daytime temperatures slightly below seasonal averages will continue through Thursday. Marine layer low clouds will spread into the inland valleys during the nights and mornings. Some light precipitation is possible late Wednesday night into Thursday morning west of the mountains, including the coastal waters. Temperatures increase for Friday into early next week, along with periods of offshore flow producing gusty east to northeast winds. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... Mostly clear this afternoon, except for a few low clouds off the Orange County coast. A coastal eddy centered southwest of the Channel Islands is transporting low clouds northwest towards Point Conception and farther north. Temperatures are generally a few degrees lower than at this time yesterday west of the mtns while in the mtns and deserts, temperatures are generally higher. Sfc pressure gradients remain onshore and some locations are reporting wind gusts 20-25 mph at this hour. A large-scale trough of low pressure continues to dominate the pattern over the western U.S. A shortwave trough moving southward in the mean cyclonic flow will reach California and Nevada on Thursday. Global models differ only slightly on the speed and trajectory of the shortwave. For Wednesday night into Thursday, deepening of the marine layer is expected ahead of the shortwave trough moving southward into California and Nevada. The higher resolution models show the potential for widely scattered light showers across the coastal waters into coastal areas for late Wednesday night into Thursday morning. High temperatures today will be similar to those of Monday, with high temperatures for Wednesday and Thursday a few degrees cooler inland from the coast as the shortwave trough brings in cooler air from the north. Friday through Tuesday...The global models develop a weak closed low somewhere in the vicinity of southern California on Friday. Significant differences in the projected location of the low continues to make the forecast uncertain. Beyond that location on Friday, there are differences on how quickly it then moves inland across northern Mexico and the southwest states as well as the projected path. By Sunday, most of the models have weakened the trough of low pressure and moved it inland. The models continue to show temperatures increasing on Friday and remaining above seasonal averages through early next week. Periods of offshore flow will be possible for Friday through early next week. However, at least for the weekend, humidities are likely to remain elevated as the low brings some moisture from the tropics into SoCal. Some model solutions indicate the potential for showers Saturday afternoon, mainly in San Diego County. At this time, the differences in model solutions inspires little confidence in the model projections. && .AVIATION... 092010Z...Mostly clear conditions are seen in most areas with scattered cumulus starting to pop up over the mountains with unrestricted vis expected. Cigs will start to redevelop after 04Z Wednesday. These low clouds will spread a little farther inland than last night with bases 1500 to 2000 feet. Clouds will slowly begin to scatter out after 15Z in coastal valleys and after 17Z at the coast on Wednesday. && .MARINE... No hazardous marine weather is forecast through Saturday. && .BEACHES... A long-period swell coming from tropical cyclone Sergio will bring increasing surf today and Wednesday and will peak Thursday into Friday. Strong rip currents and possible coastal flooding are the biggest threats. Swell and surf will rapidly subside late Friday and Saturday. For details, consult 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...PG AVIATION/MARINE/BEACHES...APR/Brotherton