935 FXUS66 KLOX 100408 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 908 PM PDT Tue Oct 9 2018 .SYNOPSIS...09/905 PM. Cooler than normal conditions will continue through most of the week then warm a bit into the weekend. Overnight and morning low clouds and fog will be patchy early in the week then becomes wide spread across the region. High surf is likely Tuesday through Friday. && .SHORT TERM (TNT-FRI)...09/902 PM. Weak ridging aloft remains over the area this evening. The latest satellite imagery shows a upper-level disturbance over the British Columbia coast. The disturbance will dip south into the region through Wednesday and the marine layer should deepen to between 4000 and 5000 feet Wednesday morning. The latest AMDAR soundings show a marine layer depth near 1900 feet deep at KLAX this evening. The disturbance moving south will spin up an lower- level trough circulation off the Central Coast late tonight. Moisture will likely wrap into the lower-level cyclonic flow rapidly overnight and into Wednesday morning. PoPs have nudged higher to mention a slight chance of rain or accumulating drizzle tonight for areas north of Point Conception. As the disturbance moves farther south into South Coast Basin, positive vorticity advection could squeeze out light rain or measurable drizzle from the deep marine layer. PoPs have also been nudged up south of Point Conception, as well. NAM BUFR time height sections shows decent omega values through the mixed layer on Wednesday morning. Wednesday looks like a day where most areas will struggle to clear and temperatures will likely be problematic. The forecast for temperatures remains unchanged for now, but it is possible that temperatures are about 3-5 degrees too warm if there are more clouds than sun. A few mountain showers cannot be ruled out Wednesday afternoon and evening, especially along the coastal slopes. Broad troughing over the region will linger into Wednesday night and Thursday. Slight chance PoPs remain in the forecast as the marine layer will deepen to near 5000 feet. Both NAM and GFS forecast guidance suggest at least slight chance of rain across the area. A deepening mixed layer with decent amounts of moisture will allow for instability with the trough to press out some light rain or measurable drizzle between Wednesday night and Thursday. Additional cooling should be expected for Thursday, and it is starting to shape up that Thursday will be mostly cloudy. An update was issued previously. No additional updates are planned at this time. ***From Previous Discussion*** Numerical guidance continues to diverge on Friday. All agree to make a weak cut-off low from the base of the trough. The EC then quickly moves the low to our south and east by Saturday morning, while the GFS moves it very slowly in an arc from our west on Friday until moves over San Diego on next Tuesday. This is one of those patterns that the models struggle with. As far as Friday goes, there will be some additional height falls and GFS and NAM indicate the surface gradients will turn offshore at about -3 mb. There will be much less of a marine layer and clouds will be mostly confined to the LA coast. Afternoon high temperatures will jump everywhere about 3 to 5 degrees. .LONG TERM (SAT-TUE)...09/154 PM. The long term forecast is very low confidence due to the stark differences in numerical guidance. The EC forecasting warmer temps and less of a marine layer due to higher heights while the GFS is the opposite due to the lower heights and cyclonic turning from the upper low. Model spread in the EC and GFS ensembles seems to indicate the EC is less certain of its solution so have tended the long range to favor the GFS, although would not be surprised to see that model speed up its solution for moving the cut-off low out of the area. Expecting the offshore winds to end by Sunday and a marine layer to return for Monday and Tuesday mornings. Temperatures will be near seasonal with a warm up is expected early in the week. && .AVIATION...10/0022Z. At 23Z, the marine layer depth was around 2500 feet deep at KLAX. The top of the inversion was at 3400 feet with a temperature near 16 degrees Celsius. Low to moderate confidence in the current forecast. Timing could be up to two to four hours earlier than forecast. IFR to MVFR conditions will likely spread into coastal terminals through 08Z, then into valley terminals through 13Z. There is a chance of conditions lowering one category between 10Z and 16Z. KLAX...There is a 40 percent chance of MVFR conditions at 03Z increasing to 90 percent by 07Z. There is a 30 percent chance of IFR conditions in drizzle or light showers between 11Z and 16Z. There is a 40 percent chance that VFR conditions could develop as soon as 17Z. Any east winds should remain less than 7 knots. KBUR...There is a 40 percent chance of MVFR conditions at 07Z increasing to 90 percent by 11Z. There is a 30 percent chance of IFR conditions in drizzle or light showers between 11Z and 16Z. There is a 50 percent chance that VFR conditions could develop as soon as 17Z. && .MARINE...09/812 PM. Moderate to high confidence that winds will remain below SCA levels across the waters through at least Saturday. Winds over the outer waters are expected to increase to near-SCA levels on Sunday. Large, moderate-period south to southwest swell will affect much of the waters beginning tonight. The swell is expected to build through early Friday, then diminish Friday night into Saturday. && .BEACHES...09/907 PM. Hazardous surf conditions including dangerous rip currents will continue through much of this week. Surf and swell will build through at least Thursday night. The increased surf and dangerous rip conditions will be from Tropical Storm Sergio. Estimates of surf heights between 5 to 8 feet with sets to 10 feet during the peak of the event. The highest surf will be observed at south and southwest facing beaches. Surf should begin to subside late Friday, but there is a chance that dangerous and strong rip currents could linger into Saturday. In addition, there will be the potential for some minor to moderate coastal flooding during peak of the high surf combined with high tides. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement in effect through Friday afternoon for zones 34-35-40-41-87. (See LAXCFWLOX). PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). High surf and dangerous rip current are likely across south and southwest facing beaches through Friday as additional swell energy from Sergio moves into the coastal waters. Minor/moderate coastal flooding will also be possible during times of high tide along low lying areas due to the combination of high surf and fairly high tide levels. Locally gusty offshore winds are possible Friday with low humidities and elevated fire danger. && $$ PUBLIC...Hall/jld AVIATION...Hall MARINE...Smith BEACHES...Hall SYNOPSIS...Kj weather.gov/losangeles