Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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153 FXUS66 KLOX 070653 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 1153 PM PDT Sat Jul 6 2024 .SYNOPSIS...06/214 PM. A long-lasting and extreme heatwave will continue across the region, and especially the interior, through much of next week. There is a high risk for dangerous heat illness and fast-growing fires. High temperatures will reach 105 to 115 across interior valleys, mountains and deserts. Dense fog may develop across some beaches during the night and morning hours. && .SHORT TERM (TDY-MON)...06/909 PM. ***UPDATE*** The marine layer has snapped back down to below 1000 feet thanks to compressional effects of the strong ridge aloft. Any eddy development tonight into Sunday morning should be much weaker than we saw today as indicated in part by the Santa Barbara to San Diego pressure gradient being much weaker this evening. At least Have adjusted the low cloud forecast accordingly with low clouds now anticipated to make it into coastal areas and perhaps sneaking into a few lower coastal valleys. Patchy dense fog is possible just about anywhere low clouds roll into tonight into Sunday morning. Smoke from the Lake fire may increase the odds of dense fog focused across the Central Coast with the potential for reduced visibility from smoke in and near Santa Barbara County. Tough temperature forecast tomorrow as model guidance shows similar temperatures into tomorrow, but todays unusual boost in marine layer influence due to a strong eddy is probably not being fully captured. There will probably be a few degrees of cooling for some interior areas in Sunday, but with record heat for those areas today, it will still be plenty hot to maintain most of the current excessive heat warnings. Lower confidence in the Santa Clarita Valley and Santa Ynez range where cooling today was greater than expected, but we may see a rebound for at least some of these areas on Sunday. Have maintained current slate of heat warnings (see NPWLOX for details) for now. ***From Previous Discussion*** Low clouds lingered early this afternoon for many coastal areas, and there were areas of smoke coming off the Lake Fire in the SBA County mtns. Otherwise, sunny skies covered the forecast area with little change expected the rest of today. The marine inversion has been low and strong today, but under the inversion there has been a broad southerly flow over the SoCal bight into VTU/L.A Counties. This along with a quickly increasing onshore flow has brought cooler temps to the inland coast and adjacent vlys early this afternoon. There has been enough cooling that many of the Heat Advisories and Excessive Heat Warnings for these areas have been cancelled. The same goes for the inland Central coast to the Santa Ynez Vly. However, high heat has been affecting the interior vlys to the mtns and deserts early this afternoon with temperatures soaring into the 105 to 115 degree range and Excessive Heat warnings continue there. A 598 dam H5 upper level high over nrn CA early this afternoon will slowly build S and into srn CA thru Mon. This upper level high will keep very hot conditions continuing for the next several days over the interior vlys to the mtns and deserts, where Excessive Heat Warnings will continue. Please see the latest Non- Precipitation Weather Message (LAXNPWLOX) for further details on the current warnings. For the coast and adjacent vlys, good onshore flow will keep temps from getting excessively hot, but will still be several degrees above normal. Pressure gradients will be quite strong onshore Sun then turn slightly weaker for Mon. By Tue, pressure gradients should be somewhat weaker and allow temps to warm up again for the vlys, where Heat Advisories may be needed. As far as cloud cover, varying amounts of night and morning low clouds and fog will affect mainly the coast some inland penetration to a few adjacent vlys. Patchy dense fog will also be possible the next couple of nights along the Central Coast. Otherwise and elsewhere, mostly clear skies can be expected, except for areas of smoke from the Lake Fire in the short term over portions of SLO/SBA Counties. .LONG TERM (TUE-FRI)...06/213 PM. The GFS and EC are in generally good agreement in the extended period. The large and strong upper level high will slowly push into srn NV for Wed then linger in this general area into Thu. The upper level hi will then move more into the Four Corners region for Fri and Sat. Srn CA will be under the western and southwestern periphery of the upper level hi thru Fri, then a weak upper level trof will develop along the CA coast for Sat. The Central Coast is expected to have night and morning low clouds and fog thru the period, with varying amounts of low clouds and fog S of Point Conception, primarily on the L.A./VTU County coast at times as a northerly flow over the Santa Ynez range should keep the SBA County S coast free of the low clouds. Low clouds may persist at some of the Central Coast beaches each afternoon as well. Otherwise, mostly clear skies are expected for Wed thru Sat. Excessive heat is expected to continue Wed and Thu, especially for the interior vlys to the mtns and deserts, and existing Excessive heat Warnings which run thru Wed for these areas may need to be extended into Thu. It also looks like Heat Advisories or even Excessive Heat Warnings may be needed for the vlys and Santa Ynez Mtns Wed and Thu as temps heat up due to to weaker onshore flow. Temps should cool down enough for Fri and Sat due to stronger onshore flow to the N and E that the only areas that may need heat products would be the L.A. County mtns and deserts. Even with cooler temps for the coast and vlys, it will still be several degrees above normal each day. && .AVIATION...07/0653Z. At 06Z at KLAX, the marine layer was 900 feet deep. The top of the inversion was at 4200 feet with a temperature of 33 deg C. High confidence in CAVU TAFs for KPRB, KPMD, and KWJF. Low confidence in all other TAFs. Flight category changes may be off by +/- 2 hours. LIFR conditions possible starting after 08Z at KSMO (20%), KLAX (30%), KLGB (20%). VLIFR conditions possible 08Z-16Z at KSBP (20%), KSMX (40%), KSBA (40%), KOXR (40%), KCMA (30%), KBUR (10%), and KVNY (10%) due to rapid shallowiing of the marine layer. Cigs/vsbys are likely (80-90%) to improve to MVFR-VFR conditions 18-22Z. There is a chance that KOXR/KSBA/KSMX (30-50%) have limited to no clearing. Nearby fires may lead to periods of MVFR/VFR smoke at terminal, especially KSBA and north. KLAX...Moderate confidence in the 06Z TAF. Timing of flight cat changes could be off by +/- 2 hours. There is a chance (30%) of 1/2SM and BKN002-BKN004 conditions thru 14Z Sun. Good confidence in any east wind component remaining under 5 kts. KBUR...Low confidence in the 06Z TAF. Cig/vis arrivals could be off by +/- 2 hours. There is 10% chance of 1/4SM and BKN002 conds 10Z-14Z Sun. There is a 40% chance of no cig/vsby arrival. && .MARINE...06/935 PM. For the Outer Waters, expecting winds to generally remain below SCA levels tonight and Sun morning. However, cannot rule out local gusts near SCA levels along the Central Coast and near Point Conception. Winds are expected to decrease overnight tonight. There is a 30% chance for SCA level winds Sunday afternoon and evening near Point Conception. By Monday, chances for SCA winds increase to around 40%, with more widespread winds through the outer waters through Tuesday night. Could see SCA winds Wednesday through Thursday as well. In the inner waters N of Pt. Sal, there is a 30% chance of SCA level winds during the afternoon/evening hours Mon and Tue, otherwise SCA conds are not expected thru Wed night. In the inner waters south of Pt Conception, SCA conditions are not expected thru Thu. However, there is a 20% chance for SCA level winds over far western portions of the Santa Barbara Channel Sunday evening. Then there is a 30% chance of SCA winds during the afternoon/evening hours Tue thru Thu in western portions of the Santa Barbara Channel, mainly from Santa Cruz Island to the SBA County south coast from Pt. Conception to Gaviota to Refugio State Beach. Areas of dense fog will continue to affect the coastal waters through Sun morning. Please reference the Marine Weather Statement for additional information. && .BEACHES...06/958 PM. A moderate southerly swell will continue to affect the Southern California coastal waters through Sunday, with a 14-16-second period this weekend. While surf is not expected to be particularly high, surf heights of up to 4 to 6 feet are anticipated at beaches exposed to southerly swell, especially the LA and Ventura County beaches. Significant wave energy with the long-period swell will combine with the elevated surf to create dangerous conditions at area beaches, with powerful and dangerous rip currents expected. This is especially the case for the south-facing beaches of LA and Ventura Counties. A Beach Hazards Statement is in effect through Sunday evening to address these concerns. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning remains in effect until 9 PM PDT Wednesday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 9 PM PDT Sunday for zones 88-351-352-375-380. (See LAXNPWLOX). Beach Hazards Statement in effect through Sunday evening for zones 354-362-366. (See LAXCFWLOX). Red Flag Warning in effect until 6 AM PDT Monday for zones 378-381. (See LAXRFWLOX). PZ...NONE. && $$ PUBLIC...Sirard AVIATION...Lewis/KL MARINE...Phillips/DB BEACHES...LP/DB SYNOPSIS...Sirard weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox