Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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076 FXUS66 KLOX 031539 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 839 AM PDT Wed Jul 3 2024 .SYNOPSIS...03/824 AM. A significant heatwave will affect the region this week and will continue through much of next week, with dangerously hot temperatures across much of the area. High temperatures will reach 95 to 105 degrees in many areas away from the coast, with highs upwards of 105 to 115 over interior valleys and foothills, including the Antelope Valley. Very warm to hot conditions could extend closer to the coast by late this week. Patchy night to morning dense fog will affect the coasts this morning and Thursday morning. && .SHORT TERM (TDY-FRI)...03/838 AM. ***UPDATE*** The marine layer continues to lower, now down to 600-800 feet based on the latest pilot reports. The inland extent of stratus was about 50% of yesterday and expecting even less Thu and Fri. Of course with the lowering of the marine layer comes lowering visibilities at the coast so there have been reports of dense fog this morning and will see more of that again tonight. One likely modification today will be to extend the interior heat warnings through next Wednesday. This includes the mountains, Antelope Valley, interior SLO County and the Cuyama Valley. Ensemble based guidance continues to show strong high pressure continuing well into next week, perhaps even beyond the current 7 day period ending next Wednesday. One interesting climate note is that the record of consecutive days of 110+ at Palmdale and Lancaster is 3, and the current forecast has all 7 days of the forecast period above 110 there, with strong chances of that continuing through the end of next week. Paso Robles record of consecutive 110+ is 5 and that will likely be broken as well. ***From Previous Discussion*** The heat wave will begin in earnest today with offshore trends at the sfc and hgt rises from an encroaching upper high. Hgts will reach 595 or 596 dam later this afternoon. Max temps will jump 2 to 4 degrees today and max temps will end up 12 to 18 degrees above normal away from the coasts. Excessive Heat Warnings remain in effect for the all non coastal areas today except for the San Gabriel Vly which will be under a Heat Advisory which goes into effect at 1100 am this morning. The marine layer will be similar tonight to this morning will only the near shore areas affected. The very strong marine layer capping inversion will extend from around 1000 to 3000 ft with temps as high as 82 degrees. Overnight lows in areas within these elevations will experience very warm overnight lows in the mid to upper 70s with some lower 80s possible. Max temps will be a little warmer on Thursday. Heat advisories will go into effect across the interior portions of the coastal sections as the marine layer retreats closer to the shore. The biggest concern on Thursday will be across the SBA south coast where a northerly offshore push across the county will bring sundowner winds to the area. Any downsloping winds will adiabatically warm the already hot air further and temps of 100 degrees will be possible. Due to this likely scenario an excessive heat warning is in effect for the SBA south coast both Thu and Fri. There will be only a bare minimum of marine layer clouds Thursday night. Again the areas between 1000 and 3000 ft will experience much warmer than normal overnight lows. Friday will be the warmest day. As 596 dam hgts combine, with warming subsidence from the upper high parked over nrn CA and only weak onshore flow. Look for 3 to 6 degrees of warming for most areas but some coastal areas may see 10 degrees of warming and if the north flow hits just right the SBA south coast could warm 20+ degrees. Highs across the far interior like the Antelope Valley,interior SLO County, and the lower mountain elevations will see highs between 108-116, 15-20 degrees above normal. Warmer coastal valleys are expected to reach 107-109. It is likely that there will be many High temperature records on Friday. Please see the product LAXNPWLOX for all the details on the heat warnings and advisories. The combination of these very hot temperatures, areas of low humidities and possible sundowner winds will lead to fire weather risks. Please see the fire weather discussion below for all the details. .LONG TERM (SAT-TUE)...03/331 AM. Not much change in the forecast during the xtnd period. Deterministic and ensemble means both indicate the upper high remaining over the state through at least Tuesday. Hgts remain steady between 596 and 597 dam. The only change is a noticeable increase in the onshore flow which will help bring the marine layer back and allow for some cooling across the coasts and lower vlys. It is likely that the heat warnings for the mtn and inland areas will have to be xtnd. The downside of the increase in onshore flow will be increased afternoon and early evening winds across the interior. This winds will, for sure, increase the fire danger. && .AVIATION...03/1527Z. At 15Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was at 4900 feet with a temperature of 29 Celsius. High confidence in CAVU TAFs for KPRB, KPMD, and KWJF. Moderate confidence in remainder of TAFs. IFR-LIFR cigs and MVFR- LIFR vsbys in low clouds and fog are expected to continue near the coast through mid-day today before dissipating, and then return tonight and continue into Thursday morning. Cig/vsby restrictions will dissipate around mid-day Thursday, with onset and dissipation timing of cig/vsby restrictions varying by +/- 2-3 hours of current forecasts. KLAX...Moderate confidence in TAF. No significant easterly wind component is expected. KBUR...Moderate confidence in TAF. && .MARINE...03/311 AM. For the Outer Waters, Small Craft Advisory (SCA) conditions are not expected through Thursday afternoon. For Thursday night through the weekend, there is a 40-50% chance of SCA winds. There is a 10-15% chance of local Gale Force wind gusts on Friday afternoon and evening. For the Inner Waters north of Point Sal, SCA conditions are generally unlikely through the upcoming weekend, though there is a 30% chance for SCA winds for Friday afternoon and evening. For the Inner Waters south of Point Conception, SCA conditions are generally not expected through the upcoming weekend. However, there is a 20-30% chance of local SCA level wind gusts across the western portion of the waters Thursday afternoon and evening. Dense fog is expected over the coastal waters for the remainder of this week during the overnight to morning hours, with a gradual decrease in the coverage of fog as the week progresses. Please reference the Marine Weather Statement for additional information. && .BEACHES...03/838 AM. A southerly swell front will overspread the Southern California coastal waters Thursday into Friday, followed by 15-17-second southerly swell persisting from late this week into the weekend. While surf is not expected to be particularly high, surf heights upwards of around 5 feet are anticipated at beaches exposed to southerly swell -- especially the LA and Ventura County beaches. Moreover, 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 beaches of LA and Ventura Counties. A Beach Hazards Statement is in effect from Thursday mid-day through the weekend to address these concerns. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning remains in effect until 6 PM PDT Monday for zones 38-88-342>345-348-351>353-356>358-369>383. (See LAXNPWLOX). Heat Advisory remains in effect from 11 AM Thursday to 6 PM PDT Sunday for zones 341-347-355-368. (See LAXNPWLOX). Excessive Heat Warning in effect from 11 AM Thursday to 6 PM PDT Saturday for zones 349-350. (See LAXNPWLOX). Beach Hazards Statement in effect from Thursday morning through Sunday evening for zones 354-362-366. (See LAXCFWLOX). Heat Advisory remains in effect until 6 PM PDT Sunday for zone 548. (See LAXNPWLOX). Fire Weather Watch in effect from Thursday evening through late Friday night for zones 349>353-376>378-381. (See LAXRFWLOX). PZ...NONE. && $$ PUBLIC...MW/Rorke AVIATION...Cohen MARINE...Lund/Smith/Lewis BEACHES...Cohen SYNOPSIS...Cohen/Smith/MW weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox