350 FXUS66 KSGX 110946 AFDSGX Area Forecast Discussion National Weather Service San Diego CA 246 AM PDT Thu Oct 11 2018 .SYNOPSIS... Cool weather will continue as low pressure dominates the West. Isolated sprinkles are possible this morning near the coast. After some offshore flow and foothill winds Friday morning, moisture from the south will bring showers Friday night through Sunday morning. Offshore flow strengthens Sunday into Monday, becoming weaker Tuesday and beyond. Combined with higher pressure aloft, that would bring blue skies and warmer weather. && .DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE... SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO COUNTIES... We have the clouds from the mountain crests westward, but they are full of holes and quite thin. The shower idea isn't looking so good, but there is still a small chance a shower could convect here and there near the coast this morning. The western low- pressure trough pattern continues and that means a relatively cool air mass over the interior. That means offshore flow for SoCal. A weak trough moves through the West today. So after a cool and partly cloudy day today, the flow turns offshore tonight and Friday. The west-facing foothills will have some impressive gusts 30 to 40 mph, with isolated higher gusts. We'll see an increase in clouds Friday, courtesy of tropical cyclone Sergio which (who?) will be staggering into mainland Mexico. A shortwave trough cuts off of the main longwave trough over California and closes off west of SoCal. It will reach into the deep moisture over Mexico and draw it into SoCal Friday night. The closed low slowly moves east and provides some energy to convert that moisture into showers. We have showers beginning Friday evening and continuing into Sunday morning, with the best chance for heavier showers Saturday. Mountains could get up to an inch of rain, but most lower elevations will be less than a half inch. There is considerable uncertainty in this amount forecast. Still not quite sold on the thunderstorm chances, but they may be coming soon to a forecast near you. Yesterday I noted the good model agreement, or consistency, but didn't have the consistency from one model run to the next. They were all giving us some rain this weekend, but when it would end was still up in the air. Now several model runs have indicated the trough will move out Sunday and take the moisture with it. Immediately in its wake will be some offshore winds (and that boosts confidence that precip will end at that time, too). As long as that big trough hovers over the West, we'll keep the offshore flow and winds coming possibly all next week. Monday looks like a pretty decent offshore wind event with some gusts in the favored foothills that could exceed 50 mph. Right now winds appear much weaker for Tuesday and beyond. Skies will become crystal clear. Daytime temps will increase Monday and Tuesday, but under northerly continental flow, we don't warm up all that much. A tepid Santa Ana. By Tuesday a few spots could touch 90, but 80s will be common at lower elevations and humidity way down. The dry air and clear nights will make for some cool nights outside of the breezy areas. && .AVIATION... 110850Z...Coasts/Valleys/Coastal Mountain Slopes...Stratus with bases 4000-6000 ft MSL and tops to 6500 ft MSL continuing through about 16Z, obscuring coastal mountain slopes. Occasional CIGS down to 2500 ft MSL and patchy -DZ possible 10-15Z. After 16Z...FEW-SCT clouds with bases 4000 ft or higher. No low cloud development expected tonight into Fri morning. Desert Mountain Slopes/Deserts...Mostly clear with unrestricted vis through fri morning. && .MARINE... No hazardous marine weather through Friday. A low pressure system will bring a slight chance of showers Friday night through Sunday morning. && .BEACHES... South swells from 200-210 degrees generated by Tropical Storm Sergio will build slightly through Friday. Combined seas are currently 1-2 ft below forecasted values and recent wave guidance has lowered the max swell from 8 ft to 6 ft. Surf of 4-7 ft with higher sets still possible as the swell peaks, though the risk of coastal flooding this morning is reduced. Strong rip and longshore currents are likely through Friday. For more details, see the Beach Hazards Statement and the Surf Zone Forecast. && .FIRE WEATHER... Offshore flow and foothill winds to develop tonight and peak late Friday morning, most favored for the west-facing foothills. Fortunately, the air will still be quite moist, so the fire growth potential stays in check. Offshore flow develops Sunday and peaks Monday. This will be a drier and stronger event, but will follow showers. Nevertheless, this will need to be monitored. && .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 this evening for Orange County Coastal Areas. High Surf Advisory from 8 PM this evening to 11 PM PDT Friday for Orange County Coastal Areas. Beach Hazards Statement through Friday evening for San Diego County Coastal Areas. PZ...NONE. && $$ PUBLIC/FIRE WEATHER...MM AVIATION/MARINE/BEACHES...SS