Area Forecast Discussion
Issued by NWS Los Angeles, CA

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054 FXUS66 KLOX 231841 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 1141 AM PDT Mon Sep 23 2024 .SYNOPSIS...23/837 AM. Low clouds will affect the coastal areas through the week with near normal temperatures, and dense fog through at least Tuesday. Inland temperatures will remain above normal through the week, warmest today through Tuesday. Otherwise, fairly benign pattern. && .SHORT TERM (TDY-WED)...23/822 AM. ***UPDATE*** The marine layer is currently between 800 and 1200 feet, but in many ways it is behaving likely it is much shallower than that. Thick fog with visibilities under 1 mile is affecting a lot of the coastal and adjacent valley areas. The most widespread dense fog with visibilities of 1/4 mile or less is occurring over the Central Coast and the Santa Ynez Valley, where a Dense Fog Advisory was issued through 10am today. Expecting most areas to see visibilities starting to improve within the next hour and clear to at least the beaches by 11am. Where the low clouds and fog will be this afternoon is a tough call. The offshore pressure trends suggest good clearing and some projections show some sort of clearing trend from northwest to southeast. Looking at the satellite picture however and the late morning cloud surge has the scent of poor beach clearing from the Central Coast to Ventura County. While coastal areas will likely see similar temperatures compared to yesterday thanks to the moderating effects of the marine layer, all other areas will be 5 to 10 degrees warmer thanks to those offshore pressure trends and building high pressure aloft. The current temperature forecast looks on track with highs in the mid 80s to mid 90s common away from the immediate coast, and the hottest spot or two approaching 100 degrees. ***From Previous Discussion*** The marine layer will be a little shallower tonight and there will be a little less clouds in the vlys. The csts, however, will remain mired in stratus with patchy dense fog. Not much excitement in the Tue/Wed fcst. At the upper levels SW flow will develop over the state as a trof forms in the E PAC and a high amplitude ridge develops over the Rockies. Tuesday`s 586 dam hgts will fall to 584 dam. There will be similar gradients Tuesday and a stronger onshore push to the east on Wed. The low cloud pattern will continue across the coasts each night through morning with a little more vly penetration on Wed due to the increase in onshore flow. There will not be too much change in temps on Tuesday. The interior will warm a little making Tuesday the warmest day there. Most coastal areas will cool a degree or two. The lowering hgts and increased onshore flow will combine to bring 3 to 6 degrees of cooling to the area on Wednesday. The marine layer will bring a split personality to temps on Wed with the csts/vlys 2 to 4 degrees blo normal and the interior 4 to 6 degrees above normal. .LONG TERM (THU-SUN)...23/313 AM. The GFS and EC ensembles and deterministic runs are in good agreement thru the xtnd period. Srn CA will be in between high pressure to the east and low pressure troffing to the west. SW flow aloft will continue through the period. Quiet weather will dominate the fcst. In fact it will be rather June like with the forecast confined to how much marine layer stratus there will be each night through morning. Those low clouds should cover the coasts each night through morning with perhaps a little better vly coverage Sunday as the onshore flow is forecast to increase to mdt-stg. Look for slight warming Thu and better warming Fri. Cooling is on tap for both days Sat and Sun. Max temps will continue cooler than normal across the csts/vlys and warmer than normal across the interior. && .AVIATION...
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23/1840Z. At 1738Z at KLAX, the marine layer was 1100 ft deep. The top of the inversion was 2700 ft with a temperature of 27 degrees C. High confidence in desert and KPRB TAFs. Moderate confidence in KSBP and KSMX. Timing of flight cat changes could be off by +/- 2 hours. There 30% chance of VLIFR conds at KSBP 07Z-15Z. Low confidence for all other TAFs. Timing of flight cat changes could be off by +/- 2 hours. Cigs could scatter and reform at KSBA, KOXR, KSMO, and KLAX through 06Z, then there is a 30-40% chance of VLIFR conds 03Z-16Z. There is a 30% chance of VLIFR conds at KCMA 06Z-16Z. There is a 40% chance of conds remaining VFR at KBUR and KVNY, if cigs do arrive, there is a 30% chance of VLIFR conds after arrival through 16Z. KLAX...Low confidence in TAF. BKN007-010 Cigs may scatter and reform through 06Z, before remaining in for the night. There is a 40% chance of 1/2 SM FG and VV002, with a 20% chance of brief 1/4 SM FG and VV002 cigs 10Z-15Z. There is a 20% chance for cigs of no VFR transition after 16Z Tue. Good confidence in no significant easterly wind component. KBUR...High confidence in TAF through 10Z, then low confidence. Timing of flight cat changes could be off by +/- 3 hours. There is a 40% chance of 1/2SM FG VV002 conds 11Z-16Z, with a 20% chance of brief 1/4SM FG VV002.
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&& .MARINE...23/928 AM. High confidence in the current forecast through early Thursday, then moderate confidence thereafter. Winds and seas will remain below Small Craft Advisory (SCA) levels through early Thursday, except for low-to-moderate (20-30 percent) chance of local SCA level W-NW wind gusts in the vicinity Point Conception, near Point Dume and into the San Pedro Channel each afternoon and evening through Wednesday. There is a moderate (40-50 percent) chance of SCA level winds Thursday afternoon through Friday for the waters beyond 10 NM offshore along the Central Coast southeast to San Nicolas Island. Additionally, there is a 30% chance of SCA level seas building over the weekend. A shallow marine layer over the coastal waters will bring at least patchy dense fog to the coastal waters at times through Wednesday morning. A marine weather statement is in effect through noon today, but there is a likely chance that areas to widespread dense fog will redevelop over the coastal tonight through Tuesday morning. && .LOX WATCHES/WARNINGS/ADVISORIES...
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CA...NONE. PZ...NONE.
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&& $$ PUBLIC...Rorke/Kittell AVIATION...Lund MARINE...Hall/Lund SYNOPSIS...Kittell weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox