Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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729 FXUS66 KLOX 171800 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 1100 AM PDT Fri May 17 2024 .SYNOPSIS...17/943 AM. A persistent marine layer will remain in place through the weekend as strong onshore flow continues across the area. Night through morning low clouds and fog will continue to be a staple of the forecast, struggling to clear from the coast each afternoon. Breezy to gusty onshore winds will occur across the interior valleys and adjacent foothill areas each afternoon and evening. Better clearing with slight warming is possible next week as onshore flow could weaken. && .SHORT TERM (TDY-SUN)...17/949 AM. ***UPDATE*** A persistent marine layer pattern with strong onshore flow will continue through the weekend as a long wave trough remains along the West Coast. Clearing will be slow or non-existent for coast and valleys with temperatures 4-8 degrees below normal, the valleys being on the higher side of that range. Interior areas will remain clear but breezy with highs 2-5 degrees above normal. ***From Previous Discussion*** Weak dynamics with the upper-level trough will start to scrape the area tonight and into Saturday morning. The dynamics with the trough will likely lift the marine layer induced cloud deck and squeeze out some drizzle. PoPs were nudged higher tonight through Saturday morning to account for the drizzle possibility. While it is less confident, there is an outside chance that mountains showers could develop on Saturday afternoon and evening, but most model solutions suggest the middle-levels of the atmosphere to be too dry at this time. Strong onshore pressure gradients will likely bring breezy to gusty onshore winds each day across the high valleys and interior portions of the area and into the adjacent foothill areas. Winds appear to remain below advisory levels again today, but winds are expected to increase on Saturday and Sunday. At this time, advisory levels could occur across the Antelope Valley and adjacent foothill areas. A wind advisory may be issued later to account for gusty southwest winds in places, such as Lake Palmdale and Sierra Pelona. At the very least, elevated fire weather conditions will continue across the interior portions of the area, such as the Antelope Valley this afternoon and evening where winds could combine with drier conditions to bring elevated fire weather conditions. .LONG TERM (MON-THU)...17/337 AM. EPS cloud cover means suggest better clearing after Monday as an upper-level trough digs south down the state. Cold air advection moving south with a decaying frontal boundary could transport enough colder air to weaken the marine inversion. Thus, confidence continues to grow for temporary break of May Gray for the early half of next week. GEFS ensemble pressure gradients suggest onshore pressure gradients weakening for Tuesday and Wednesday. The weakening onshore gradients should promote an earlier clearing of the marine layer stratus for the coastal and valley areas. Gusty northerly winds will be possible across southern Santa Barbara County and through the Interstate 5 Corridor during evening and morning hours between Monday night and Wednesday morning. The forecast still takes a conservative approach for next week as there is a spread of the possible outcomes in the forecast ensembles for Tuesday and Wednesday, but if the ensembles continue to trend this direction, the changes to the forecast should occur and a warming trend with less clouds should be expected. && .AVIATION...17/1759Z. At 1735Z at KLAX, the marine layer was 2800 ft deep. The top of the inversion was 5400 feet with a temperature of 17 C. Overall for the 18Z TAF package, high confidence for desert TAFs and moderate confidence in coastal/valley TAFs. Lower confidence for coastal/valley sites due to uncertainties with flight category changes with the marine layer stratus. KLAX...Moderate confidence in 18Z TAF. There is a 40% chance that MVFR CIGs do not dissipate this afternoon. Timing of return of MVFR CIGs this evening could be +/- 2 hours of current 03Z forecast. No significant easterly wind component is expected. KBUR...Moderate confidence in 18Z TAF. Timing of dissipation of MVFR CIGs this afternoon could be +/- 1 hour of current 21Z forecast. For tonight, timing of return of MVFR CIGs could be +/- 2 hours of current 05Z forecast. && .MARINE...17/335 AM. In the Outer Waters, rather high confidence in the forecast. Small Craft Advisory (SCA) conditions are not expected thru Sun. There is a 30-40% chance of SCA winds/seas in the outer waters Sun night/Mon, and SCA conds are likely Tue. For the Inner Waters N of Pt. Sal, high forecast confidence. Winds and seas are expected to remain below SCA levels thru Mon night, with a 20-30% chance of SCA winds Tue. In the Inner Waters S of Pt. Conception, moderate to high forecast confidence. There is a 20-30% chance of SCA level winds in western portions of the SBA Channel in late afternoon/eve hours Mon and Tue. Otherwise, SCA conds are not expected. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...MW/Hall AVIATION...RAT MARINE...DB SYNOPSIS...Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox