FXUS66 KLOX 012218 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 318 PM PDT Sun Sep 1 2024 .SYNOPSIS...01/145 PM. Temperatures will trend upwards over the next few days, with hazardous heat occurring Wednesday through Friday, and as early as Tuesday for the western San Fernando Valley. The most dangerous heat will occur Thursday across valley and foothill locations. Low clouds and fog will occur at the coasts tomorrow morning, followed by mostly clear skies Tuesday morning onward. Temperatures will start to fall next weekend. && .SHORT TERM (TDY-TUE)...01/318 PM. An Excessive Heat Watch is in effect for the Western San Fernando Valley starting Tuesday and lasting through Friday. Starting Wednesay, an Excessive Heat Watch has been issued for all non- beach locations of San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties, lasting through Friday. The trough of low pressure currently spinning off the coast of the OR- CA boarder will travel eastward over the next few days. This will allow for high pressure to build over the region and onshore pressure gradients will trend downwards, with the potential to flip to offshore at times. In response, temperatures will trend upwards through mid- to-late week. By Wednesday moderate- to- major HeatRisk is likely to be widespread, and temperatures will be around 8 to 15 degrees above normal everywhere except for the Central Coast. Temperatures will build to the mid 70s to upper 80s at the coasts, 90s across the inland coastal plains, and 96 to 108 for the valleys and deserts. Patchy low clouds and fog will impact the coastal plains again tonight through tomorrow morning, then Tuesday morning onward clouds will largely be confined to the beaches along Central Coast. Elevated cumulus clouds are currently forming over northeastern Los Angeles County, however the layer of moisture in the atmosphere is both elevated and shallow, thus showers or thunderstorms are not expected. Similar clouds may occur again each day. Sundowner winds are expected during the evenings across the southwestern Santa Barbara County coast. Localized NW-N gusts of 30 to 45 mph are likely tonight for particularly wind prone areas such as the Gaviota RAWS, but the winds are not expected be widespread enough to warrant a wind advisory. Monday and Tuesday night, weaker gusts to 20 to 30 mph are expected for the region. Elevated fire weather conditions are anticipated for valleys, mountains, deserts, and the SBA County Southwestern coast due to the heat and dry conditions through Monday, and concerns will increase further Tuesday and Wednesday. .LONG TERM (WED-SAT)...01/314 PM. Thursday is expected to be the warmest day of the heatwave for much of the region, as a result of peaking 500 mb heights and near neutral to weakly offshore flow. An Excessive Heat Watch is in effect for all non- coastal locations of San Luis Obispo, Santa Barbara, Ventura, and Los Angeles Counties, for Wednesday through Friday. In addition, warm overnight low temperatures will bring little relief from the heat. There is about a 40-60% change of heat advisories being issued for coastal locations, especially those south of Point Conception on Thursday. Wednesday through Friday, along the Central Coast, expect daytime highs at the coasts to be in the mid 70s to 80s, and 90 to 106 for inland areas. South of Point Conception, high will be in the 80s to mid 90s at the coasts, and mid 90s up to 112 elsewhere. Temperatures will be the highest for valley locations, especially the western San Fernando Valley, where there is a small chance (20 percent) for temperatures to reach upwards of 115 degrees or even locally higher on Thursday. There is only moderate confidence in temperatures for Friday and Saturday. There is a 20-30 percent chance that the ridge will break down quicker the anticipated, which would result in cooler temperatures on Friday and more rapid cooling for the upcoming weekend. Regardless, there is moderate- to-high confidence that heat impacts will be below advisory level for the region by Sunday. Friday through Sunday, there is a 10 percent chance of thunderstorms for the northeastern portion of Los Angeles County. Lingering moisture trapped under the ridge, that has allowed for cumulus cloud build- ups, may be able to produce isolate thunderstorms if the trough passing to the north is able to break down the capping inversion. && .AVIATION...01/1708Z. At 1615Z at KLAX, the marine inversion was 1000 feet deep. The top of the inversion was at 4100 feet with a temp of 27 deg C. For 18Z TAF package, high confidence in valley/desert TAFs, but low to moderate confidence in coastal TAFs. Return of CIG/VSBY restrictions tonight could be +/- 4 hours of current forecasts. There is a 40% chance that CIG and/or VSBY restrictions do not develop tonight at any and all coastal sites. KLAX...Overall, moderate confidence in 18Z TAF. High confidence in VFR conditions through this evening. For tonight, high confidence in return of CIG/VSBY restrictions, but low confidence in timing (could be +/- 4 hours of current 12Z forecast) and flight category (equal chances of IFR or LIFR). No significant easterly wind component is expected. KBUR...High confidence in 18Z TAF as CAVU conditions are anticipated through the period. && .MARINE...01/1212 PM. For the Outer Waters, moderate to high confidence in current forecast. This afternoon through Monday night, high confidence in Small Craft Advisory (SCA) level winds. For Tuesday through Friday, there is a 40-60% chance of SCA level winds. For the Inner Waters north of Point Conception, moderate to high confidence in current forecast. Today through Monday, there is a 20-30% chance of SCA level winds in the afternoon and evening hours. For Tuesday through Friday, high confidence in winds and seas remaining below SCA levels. For the Inner Waters south of Point Conception, moderate to high confidence in current forecast. Across the western half of the Santa Barbara Channel, there is a 60-80% chance of SCA level winds late this afternoon and evening and a 40-60% chance of SCA level winds late Monday afternoon and evening. Otherwise for the Inner Waters south of Point Conception, high confidence in winds and seas remaining below SCA levels through Friday. Patchy dense fog will continue to impact the coastal waters the next few days, mainly in the night and morning hours. Visibilities of one nautical mile or less will be possible. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Watch in effect from Wednesday morning through Friday evening for zones 38-88-342>345-348-351>353-356>358-368>371-373>383-548. (See LAXNPWLOX). Excessive Heat Watch now in effect from Tuesday morning through Friday evening for zone 372. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Monday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Tuesday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...Schoenfeld/Munroe AVIATION...RAT MARINE...RAT SYNOPSIS...Schoenfeld weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox