604 FXUS66 KSGX 261829 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 1000 AM PST Tue Dec 26 2023 .SYNOPSIS... High pressure aloft over the western states will continue dry weather through Friday with high clouds at times and patchy night and morning coastal low clouds and fog. Temperatures will be slightly above average. A low pressure system from the west will bring cooling and showers Saturday with additional chances of showers next week. High surf will occur at times along the coast Thursday through early next week with possible associated coastal flooding. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... High clouds were moving over the region but otherwise fair weather was occurring with light winds prevailing. Highs will be slightly warmer today versus Monday and generally be at or slightly above normal. The high pressure ridge will continue over the Western US from SoCal through Montana through Friday as the upper low moves east in the NE Pacific. Temperatures will continue to be a little above average, even though periodic high clouds will temper the daytime temps somewhat. Confidence is growing for the tail end of the trough to be far enough south for precipitation this weekend, especially with the negative tilt to the trough over California. Around 80-90 percent of the ensemble solutions (ENS/GEFS/CMC) have at least some measurable precipitation west of the mountains Saturday though only around 20 percent have at least 0.50" in the Orange County and lower farther east and southeast. Orographics will be somewhat limited as the winds will not be very strong with this system and mostly on west- facing slopes (850 MB winds mostly 10-20 knots). Snow looks rather limited as the 50th percentile 700 mb among the ensembles is -2 C, and most of the moisture will be the expected snow level of around 7000 feet MSL. Some cooling will occur with the trough, though high temperatures each day will still only be slightly below average then. For next week, there will likely be an a progressive pattern with low pressure troughs moving east across the East Pacific into the Western United States, with SoCal being most likely on the south end of the troughs. Models/ensembles disagree substantially with timing, but regardless we could have a couple rounds of precipitation next week. && .AVIATION... 261630Z...Variable high clouds at or above 20000 feet MSL through Wednesday morning. Coast and western valleys...Patchy low clouds after 04Z tonight into Wednesday morning. Local and intermittent cigs 1200-1600 feet MSL with occasional vis 3-5SM BR. && .MARINE... Two large, long period, west swells will arrive Thursday and again Saturday. Peak swell heights of 8 to 13 feet can be expected in the outer waters, and inner waters south of Point Loma. With such a long period, this should not pose a hazard on open water. && .BEACHES... Two large, west swells with a long period will arrive Thursday and again Saturday. They will generate large breaking surf, especially in southern San Diego County, where sets of 9-12 feet (locally higher) can be expected. This would produce strong rip currents and dangerous swimming conditions, as well as beach erosion and flooding, especially during high tides. The surf will begin to subside on Sunday, then rapidly diminish Monday. && .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...Maxwell AVIATION/MARINE/BEACHES...MM