FXUS66 KLOX 121603 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 903 AM PDT Sat Apr 12 2025 .SYNOPSIS...12/436 AM. Strengthening onshore flow will bring a cooling trend into early next week. Night through morning low clouds will become a staple of the forecast over the weekend, pushing into the coastal slopes of the mountains by mid week. A cooler weather pattern is expected through much of next week as a series of low pressure systems move over the region. Night through morning drizzle or afternoon and evening mountain showers cannot be ruled out for periods next week. && .SHORT TERM (TDY-MON)...12/902 AM. ***UPDATE*** The marine inversion was around 1400 ft deep this morning. There was a good onshore push overnight with 24-hour pressure gradient trends of +3.3 mb LAX-DAG as of 15Z. A pronounced eddy in the low cloud field was evident this morning as well, with the center of the eddy around Santa Barbara Island. Marine layer clouds were much more organized this morning and covered just about all coastal areas (exception the SBA County S coast) and pushed inland to some of the adjacent vlys. Extensive low clouds also covered the southern Salinas Vly eastward to near the Kern County border. The low clouds should burn off and clear off the coast this morning, altho some beaches over L.A. County may have only partial clearing. Elsewhere and otherwise, mostly sunny skies with some hi clouds at times can be expected through this afternoon. There were some gusty N to NE winds this morning over the SBA S coast around Gaviota and also in the SLO County mtns. Overall, winds were light to breezy onshore this morning, with all areas expected to have breezy to gusty W-SW winds this afternoon as onshore gradients increase thru the day. Will update the zones to remove dense fog from the VTU/L.A. County coast and adjacent vlys this morning, otherwise the forecast in the short-term looks on track. ***From Previous Discussion*** Night through morning low clouds and fog will become a staple of the forecast as moderate to strong onshore flow is likely to develop across the region. While gradients will weaken slightly over the coming days, onshore flow and a well established marine intrusion will continue. A cooling trend is very likely to persist through the weekend. A shortwave trough moving south of Aleutian Islands this morning will drop down into the region late in the weekend, cutting off from the flow off the California coast between Sunday and Monday. This trough will reinforce onshore flow and likely deepen the marine layer depth. The trough will likely stall out off the coast for several days and keep a cooler weather pattern in place. .LONG TERM (TUE-FRI)...12/437 AM. A series of cutoff troughs of low pressure are expected to move over the region for next week. There is quite a bit of uncertainty with the finer details of the forecast. Confidence remains high in a cooler weather pattern lingering as cluster analysis suggests a broader troughing pattern lingering through much of the week. The uncertainty comes from the exact movement of upper-level low pressure systems. Night through morning drizzle or mountain showers and thunderstorms cannot be ruled out entirely given the pattern. The latest forecast ensembles have a few members generating precipitation for the first trough moving over the region between Tuesday and Wednesday, but this is likely underdone due to the convective nature of the air mass. In the latest deterministic solutions, there are periods of time where a difluent flow pattern develops ahead of a 500 mb cold pocket approaching -22 degrees Celsius. The current forecast emphasizes a deeper marine layer with a cooler weather pattern lingering, but this will be need to monitored closely. As we get out into late next week, a stronger cutoff low will likely move over the region. This could be the system that could bring a higher chance of precipitation. More than of the forecast ensembles have QPF with the system for late next week. There is a also a chance that this system could bring snow levels down to the 4000 foot level, as well. About a fifth of the EPS members generate snow for KSDB. As stronger onshore flow will likely develop with the trough, gusty southwest winds are possible for the interior portion of the area. EPS wind gusts means approach wind advisory criteria for several days late next week for KPMD and KWJF. While the forecast goes with NBM values for the current time due to the uncertainty, future shifts may need to take a closer look at the finer details as we get closer into the time period. && .AVIATION...12/1310Z. At 12Z at KLAX, the marine layer was around 1500 feet deep. The top of the inversion was around 2800 ft with a temp of 18 C. Low clouds were widespread in all coastal areas except for the south coast of SBA County, and in the Santa Ynez, Salinas and San Gabriel Valleys. Clouds may push into the valleys of VTU County and the San Fernando Valley for a couple of hours around daybreak. Conds were mostly IFR to LIFR, with some VLIFR conds in areas north of Pt. Conception and in the valleys. Skies should clear by mid morning in the valleys and late morning on the coastal plain. However, clouds may linger at some beaches into the afternoon. Expect a deeper marine layer tonight, with widespread low clouds and fog in coastal and most valley areas. Conds will be mostly low MVFR to high IFR, except LIFR to VLIFR in the valleys and in some areas north of Pt. Conception. KLAX...Low to moderate confidence in the 12Z TAF. There is a 30% chance that cigs will linger until at least 19Z, and a 10% chance they will linger thru the afternoon. There is a 30% chance that cigs this evening will arrive as early as 03Z. No significant east wind component expected thru the period. KBUR...Low confidence in the 12Z TAF. There is a 30% chance that skies will remain clear this morning. There is a 30% chance that cigs this evening will arrive as early as 07Z. && .MARINE...12/856 AM. For the outer waters, low-end GALE force wind gusts are expected thru this evening. Thereafter, Small Craft Advisory (SCA) level winds and seas are expected thru Sunday, with SCA level seas likely lingering into Sun evening. SCA conds are not expected late Sun night thru Wed. For the inner waters N of Pt Conception, SCA level seas will likely continue thru tonight. Winds will likely (80% chance) reach SCA levels this afternoon/eve, with a 20% chance of GALE force gusts. SCA conds are not expected Sun thru Wed night. For the Santa Barbara Channel, SCA level winds are likely (70% chance) in western portions this afternoon thru late tonight, with a 30% chance of SCA winds pushing into eastern portions. SCA conds are not expected Sun thru Wed night. For the southern inner waters, there is a 30% chance of SCA level W-NW wind gusts this afternoon/eve from Anacapa Island to Malibu, and a 20% chance of SCA winds pushing into the Santa Monica Basin and across the outer portion of the zone. Otherwise, SCA conds are not expected thru Wed night. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Beach Hazards Statement in effect until 9 PM PDT this evening for zones 87-354-362-366-367. (See LAXCFWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM this afternoon to 3 AM PDT Sunday for zone 650. (See LAXMWWLOX). Gale Warning in effect until 9 PM PDT this evening for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...Hall/Sirard AVIATION...DB MARINE...DB/Lund SYNOPSIS...Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox