FXUS66 KLOX 060312 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 812 PM PDT Thu Sep 5 2024 .SYNOPSIS...05/135 PM. It will be dangerously hot through the weekend with only slow cooling early next week. Normal temperatures may not return to some areas until next Thursday or Friday. && .SHORT TERM (THU-SUN)...05/212 PM. The hot temperatures lived up to their billing today and then some as light offshore flow in the morning combined with extremely hot temperatures aloft to roast most of southern California in triple digit heat. Only the immediate coastal areas were spared the extreme heat, though even there temperatures were 5-10 degrees above normal. No official high temperature records so far but Woodland Hills is within a degree of matching the record of 117. Overnight lows were impressively warm this morning, especially in the thermal belt at the top of the marine inversion between 1500 and 3000 feet. In those areas lows were around 90 degrees, and likely slightly warmer tonight. The main adjustment the to the forecast today was to extend most of the advisories and warnings south of Pt Conception through Monday as models only show minor cooling, mainly on Saturday. Highs Friday are expected to similar to slightly warmer than today as offshore gradients will be about 1 mb stronger than today. Records are warmer tomorrow as it will be the 4 year anniversary of the extreme heatwave in 2020 when several all time records were set. So it's not impossible but like today it's unlikely. Models continue to advertise light onshore trends Saturday but all this will likely do is lower temps from ridiculously hot to extremely hot, or roughly 1-4 degrees of cooling. Then Sunday models indicate a slight bump in offshore flow, though currently the temperatures aloft are slightly cooler than today. With these offsetting factors max temps could either stay about the same as Saturday or smaller chances of them either being slightly warmer or cooler. Either way, high temperatures will be 15-20 degrees above normal, and overnight temperatures will remain extremely warm (80s to low 90s), especially in areas that are above 1000-1500 feet elevation. Lastly, there still is a 10-15 percent chance of an afternoon thunderstorm across eastern mountains and deserts this weekend as the upper level pattern shifts and pulls in some moisture from the southeast. .LONG TERM (MON-THU)...05/219 PM. A slow cooling trend is expected next week but it will take well into the middle next week before temperatures are back to normal levels, especially away from the beaches. A low pressure system is expected to deepen along the West Coast Tuesday and Wednesday that will provide that cooling, though there is increasing uncertainty later in the week with regard to how far south that trough will extend and how quickly it will exit. Certainly no rain expected, but confidence on the impact on temperatures remains on the lower side from midweek on. && .AVIATION...05/2326Z. At 2257Z at KLAX, the marine inversion was 800 feet deep. The top of the inversion was at 1700 feet with a temperature of 38 deg C. Low to moderate confidence in 00Z TAFs for KSMX and KSBP. There is a 40% chance for VLIFR conds at KSMX between 07Z and 15Z if cigs arrive. There is a 30% chance KSMX remains VFR thru the forecast period. Arrival of cigs may be off +/- 3 hours from current fcst, if they develop. There is a 20% chance for VLIFR- LIFR conds at KSBP between 08Z and 14Z. High confidence in all remaining sites for the 00Z TAFs. There is a 10% chance for brief vsbys of 3SM to 5SM between 12Z and 16Z at KLAX, KSMO, and KLGB. KLAX...High confidence in the 00Z TAF. There is a 10% chance for brief vsbys of 3SM to 5SM between 12Z and 16Z. Any east wind component should remain under 5 kts. KBUR...High confidence in the 00Z TAF. && .MARINE...05/811 PM. In the Outer Waters from the Central Coast to San Nicolas Island, moderate confidence in the forecast. Small Craft Advisory (SCA) level winds are expected thru late Fri night. There is a low chance (10-20%) of localized low-end Gale Force wind gusts late tonight and again tomorrow night in the two southern zones from Pt Conception to San Nicolas Island. There will likely be a lull in the winds Saturday morning, but moderate confidence in SCA level winds picking back up Sat afternoon and lasting thru late night hours Sun, with a lull possible Sunday morning. There is a 20-30% chance winds remain above SCA level in the northern zone from Pt Sal to Pt Piedras Blancas from late Sun thru Mon night. Higher confidence in winds remaining above SCA level in the two southern zones from Sun night thru at least Mon night. In the inner waters N of Pt. Sal, moderate confidence in the forecast. There is a 40-50% chance of SCA level winds tomorrow afternoon thru evening, and a 30-40% chance of SCA level winds in the afternoon thru evening hours Sat and Sun, with lower chances on Mon. In the inner waters S of Pt Conception, moderate confidence in the forecast. SCA level winds are likely to continue thru late tonight. Then, winds will likely (60-70% chance) reach SCA levels again in Western and Southern portions of the Santa Barbara Channel, and from Anacapa Island to the San Pedro Channel tomorrow afternoon thru late night. There is a 40-50% chance of SCA level winds in the same areas Sat thru Mon in the afternoon thru evening hours, with best chances in the Western portion of the Santa Barbara Channel. Patchy dense fog may continue to affect portions of the coastal waters over the next few days, mostly during the night and morning hours in the northern waters. Visibilities of one nautical mile or less are likely at times. && .FIRE WEATHER...05/920 AM. A long duration heat wave continues to ramp up towards the Friday peak, with minimal improvement after through Saturday or Sunday. Peak high temperatures between 107 and 117 will become common over the valleys, lower mountains and deserts. Inland coastal plains will see peak highs between 93 and 103, including the Santa Barbara foothills. Overnight lows will bring little relief to the foothills and deserts, with lows in the 80s common and some locations not going below 90. Humidities will lower as well, with minimum humidities generally in the 8 to 15 percent range over the valleys and mountains and poor to minimal overnight recoveries. Sundowner winds will increase over southern Santa Barbara County, peaking tonight and Friday night with gusts between 25 and 40 mph common over most of the Santa Ynez Range. Otherwise, stronger than usual diurnal winds are expected, with west to northwest gusts between 15 and 30 mph common over most areas each afternoon and evening, and some local north to northeast gusts of 15 to 25 mph each night. With high mixing heights up to 18,000 feet, there is also high potential for erratic plume-dominated fire behavior especially in the mountains. The chance for Red Flag conditions and durations has increased to 80 percent over the areas of most concern, including southern Santa Barbara County, the Santa Monica Mountains, and the Santa Susana Mountains. For the rest of the mountains and foothills, while winds will limit the potential for classic red flag criteria, there is a history of large fires with similar weather conditions during this time of the year, especially considering the plume dominated fire potential. So a Red Flag Warning will be in effect to handle this threat. All other areas away from the beaches will have elevated to isolated and brief critical fire weather conditions. Lastly, there is a 5 to 15 percent chance of dry lightning thunderstorms Friday through Monday over the mountains and deserts, mainly over Los Angeles County and over the weekend. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning now in effect until 8 PM PDT Monday for zones 38-88-351>353-356>358-362-366>380-548. (See LAXNPWLOX). Heat Advisory remains in effect until 8 PM PDT Friday for zones 341-347. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 8 PM PDT Saturday for zones 342>345-348-381>383. (See LAXNPWLOX). Heat Advisory now in effect until 8 PM PDT Monday for zones 349-350-355. (See LAXNPWLOX). Red Flag Warning in effect until 10 PM PDT Saturday for zones 342-345-349>353-369-370-375>381. (See LAXRFWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Friday for zones 645-650-655. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Saturday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...MW AVIATION...Lewis MARINE...Lewis/Sirard FIRE...Kittell SYNOPSIS...MW weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox