597 FXUS66 KLOX 291127 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 427 AM PDT Tue Jul 29 2025 .SYNOPSIS...29/225 AM. An onshore flow regime will keep a persistent marine layer depth in place. The marine layer depth will thin some through midweek as an upper-level ridge over the Southeast builds into the Four Corners region. Meanwhile, an upper-level trough of low pressure will serve to keep onshore flow in place and night through morning low clouds and fog in the forecast for most coastal and valley locations. Away from the coast, a slow warming trend will take shape due to the influence of the high pressure system. && .SHORT TERM (TDY-THU)...29/224 AM. Southwest flow aloft continues across the region this morning, keeping an onshore flow regime and a persistent marine layer depth in place. Low clouds and fog are a less-entrenched early this morning versus the last several nights, but clouds should return to most coastal areas and some valley areas later this morning as moderate onshore gradients continue across the region. An eddy circulation remains intact across the southern California bight, and clouds should fill in across the bight through daybreak. The latest AMDAR soundings from KLAX indicate a 1000 foot deep marine layer depth currently, which is a little lower than what the latest NAM BUFR time height sections indicate. The eddy should deepen the marine layer depth to around 1500 feet deep later this morning, which would represent some thinning of the marine layer depth. 1000-500 mb thickness values are starting to climb and clamp down on the marine layer depth as an upper-level ridge over the southeastern United States expands and builds west into the Four Corners region. The marine layer depth will thin through Thursday as subsiding air aloft with the high pressure system presses down on top of the marine layer. Away from the coast and into the valleys, mountains, and desert, a slow and gradual warming trend will develop, but closer to the coast, temperature trends will be much more muted as the high pressure system will serve to sharpen and strength the marine inversion. Along the Central Coast, clouds will struggle to clear each day, likely shrouding portions of the Central Coast in clouds through much of the week as EPS cloud cover means suggest. This will keep temperatures trends near persistent for the coastal sections and coastal valleys. Strong onshore flow should persist for Central California as a weak upper-level trough remains over the Central Coast and to the northwest. A cooler air mass to the northwest will keep higher pressure at the surface over the northeastern Pacific, while a thermal low pressure system will continue across southeastern California. This will set up a tighter northwest surface gradient across the area. Gusty Sundowner winds will develop each night through Wednesday night as KSBA-KSMX surface pressure gradients tighten. If traveling across southern Santa Barbara County the next several evenings, watch out for gusty cross winds, especially west of Goleta out toward Gaviota. Gusty northwest winds, which could develop rapidly, should be expected at Refugio and Gaviota State Beaches each evening. If planning outdoor activities, it may be best to schedule these outside the windy times. .LONG TERM (FRI-MON)...29/224 AM. The latest forecast ensembles indicate 500 mb heights climbing between Thursday and the weekend. Interior portions of the area will see temperatures climb above normal for late week as the high pressure system builds into the Four Corners region through the week, and then build west into the Desert Southwest on Friday. While most of the warming will take place outside of the marine, southwest flow aloft will remain in place and keep some marine influence in the forecast. Cluster analysis of the 500 mb pattern suggests the persistent trough over the northeastern Pacific Ocean remaining anchored in place through at least the weekend, and night through morning low clouds and fog should persist. Cluster analysis does hint at a pattern shift for early next week as Clusters 1 and 3 would shift the high pressure system farther to the north and west. This would produce much hotter solutions across the region. The pattern, if it develops, could confine low clouds and fog to the coast and heat up the valleys. In particular, Cluster 3 could open up the window for monsoonal flow to work its way into southern California. For now, the long term period forecast goes with NBM values. && .AVIATION...29/1126Z. At 0834Z at KLAX, the marine layer was around 900 ft deep. The top of the inversion was around 3300 feet with a max temperature of 23 C. High confidence in VFR TAFs for KWJF and KPMD. Low confidence in TAF for KPRB through 16Z, where there is a 40% chance for LIFR to IFR cigs. High confidence in TAF thereafter. Moderate confidence in remaining TAFs. Timing of flight cat changes may be off +/- 2 hours through 21Z. Minimum cig height may be off +/- 300 ft. There is a chance for no low clouds this morning at KSBA (30%), KOXR (15%), and KCMA (20%), KBUR (30%), and KVNY (30%). Patchy marine layer clouds may cause cigs to frequently vary between BKN and SCT this morning. Low confidence in arrival times of cigs tonight (+/- 3 hrs), highest uncertainty south of Point Conception. There is a 30% chance for no low clouds tonight at KLAX, KSMO, KLGB, and a 20% chance for low clouds tonight (after 06Z) at KOXR and KCMA. KLAX...Moderate confidence in TAF. Cigs may vary from BKN to SCT through 18Z. Transition to VFR may be anywhere from 16Z to 20Z. Arrival of cigs tonight may be off +/- 3 hrs and heights +/- 300 ft. There is a 30% chance of no low clouds after 00Z through 18Z Wed. Moderate confidence in any east wind component remaining below 7 kts. KBUR...Moderate confidence in TAF. Arrival and departure of cigs may be off +/- 2 hours. Minimum cig height may be off +/- 300 ft. There is a 30% chance for no low clouds. && .MARINE...29/147 AM. High confidence in Small Craft Advisory (SCA) winds across the Outer Waters through the weekend, with brief lulls possible in the morning hours. There is a low chance (15%) of Gales around Point Conception and south to San Nicolas Island Wednesday evening. Seas are likely to build to 6 to 8 feet across the Outer Waters tonight and last through the week, then building to 8 to 10 feet this weekend. For the nearshore waters north of Pt Sal, moderate to high confidence in SCA level winds during the afternoon and evening hours each day through the weekend. High confidence in SCA level winds across the western portion of the Santa Barbara Channel each afternoon and evening through Thursday, with lower chances Friday. Low to moderate chances that SCA winds reach eastern portions of the Channel through Thursday (most likely Wednesday). Local SCA level wind gusts are possible Wednesday afternoon and evening around Pt Dume and through the San Pedro Channel, otherwise no hazardous conditions expected for the inner waters of the Los Angeles and Orange County coasts. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory in effect from 6 PM this evening to 3 AM PDT Wednesday for zones 349-351. (See LAXNPWLOX). PZ...Small Craft Advisory in effect from 3 PM this afternoon to 9 PM PDT this evening for zones 645-650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Thursday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...Hall AVIATION...Lewis MARINE...Lewis SYNOPSIS...Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox