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Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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932 FXUS66 KLOX 050355 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 855 PM PDT Thu Jul 4 2024 .SYNOPSIS...04/739 PM. 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, and upwards of 105 to 115 across interior valleys and foothills, including the Antelope Valley. Patchy night to morning dense fog will develop near the coast through at least Friday morning. && .SHORT TERM (THU-SUN)...04/854 PM. ***UPDATE*** Temperatures continued to climb over the far interior areas today as high pressure builds further with 598 dam heights pushing in from the northwest.Highs reached up to 111 degrees F in the Antelope Valley, with 100s common through the interior. The mountains were also quite hot, with highs up into the 90s-100s common. Further west in the valleys, temperatures actually cooled as much as 10-12 degrees in response to a deepening marine layer (1500 ft) with onshore flow. Tonight, winds will shift to the north leading to sundowner winds along western portions of the Santa Ynez range and Santa Barbara south coast. Expecting gusts 45 to 50 mph, and a Wind Advisory was issued for tonight/Friday morning for this area. These north winds will push the hot, dry airmass to the coasts, and therefore Friday still appears to be the hottest day for the majority of the region. Heights actually fall slightly on Friday, with weaker onshore flow (LAX-DAG gradient falls to around 4 mb from 7 mb this afternoon) which may make for a tricky forecast near the coast. Sundowner winds tonight will lead to hot, dry conditions for the Santa Barbara south coast, with highs pushing into the 90s Friday, and most coast and coastal valley areas are expected to jump 10 to 20 degrees warmer. An increase in onshore flow will start cooling the coasts Saturday. Current forecast looks on track, with no significant changes needed. ***From Previous Discussion*** High res models continue to indicate significant warming in all areas Friday, including the beaches as onshore flow weakens considerably and a light northerly flow develops that will provide an additional temperature boosting factor. Highs expected to jump as much as 15-20 degrees above today`s levels for coastal areas, with special emphasis along the Central Coast down to southern Santa Barbara County where highs could reach near 100 away from the immediate coast. Farther inland expecting temperatures approaching 115. Forecast high for Woodland Hills is 111 Friday but the latest ensemble projections show around a 10% chance of reaching 115. Friday has perhaps the best chance to have widespread broken records as the current records are reasonably within reach in many areas. Saturday will be another interesting day as models are showing several degrees of cooling at lower elevations, especially south of Pt Conception. Onshore flow is slightly weaker in the morning but 3mb stronger to the north and east in the afternoon so a lot will depend on how quickly the onshore trends kick in. Forecast calls for 3-6 degrees of cooling most coast/valley areas Saturday. This still falls squarely in the Excessive heat warning range for valleys but just low end heat advisories for inland coastal areas. Interior areas will not feel these effects so little if any change or possibly even warmer there. Chances for broken records Saturday are lower in many areas due to the cooling expected for coast and some valleys and much higher record values due to a heat wave in 2018. Additional onshore trends expected Sunday leading to more cooling for coastal areas and spreading farther inland. May have to re- evaluate some inland coastal heat products on Sunday as temperatures in the mid 70s to mid 80s would be below heat advisory levels. Onshore flow will reach interior areas but with temperatures still at or above 110 Excessive heat warnings there will still be needed. The increase in onshore winds there in the afternoon, particularly across the interior mountains and Antelope Valley, will increase the fire risk in those areas. .LONG TERM (MON-THU)...04/209 PM. The overall pattern next week remains quite hot across the interior and certainly well above normal closer to the coast. After Sunday`s onshore flow increase, models have been pretty consistent indicating lighter, though still present, onshore flow the rest of next week. Meanwhile, the upper high really doesn`t move or weaken very much. As a result, interior areas will continue to scorch with highs near or above 110 and warmer coastal valley highs will reach around 105 each day. Lower confidence with coastal temperatures due to the uncertainty with the marine layer and possible eddy development over the southern coastal waters, but highs there should be at least 4-8 degrees above normal all week. && .AVIATION...05/0207Z. At 00Z at KLAX, the marine layer was 800 feet deep. The top of the inversion was at 4000 feet with a temperature of 31 deg Celsius. High confidence in CAVU TAFs for KPRB, KBUR, KVNY, KPMD, and KWJF. Expect somewhat less low cloud coverage tonight, mainly affecting coastal sections of L.A. and VTU Counties, and possibly the Central Coast. Most likely cigs will be IFR/LIFR. There is a 40% chance of VLIFR at coastal sites late tonight and early Fri. From 04Z-09Z this evening, there may be areas of MVFR vsbys due to smoke and haze from holiday fireworks celebrations. KLAX...Moderate confidence in the 00Z TAF. Cigs may arrive as early as 03Z, and as late as 09Z. There is a 50% chance of VLIFR conds 09Z-14Z Fri. KBUR...High confidence in the 00Z TAF with VFR conds thru the period, except there is a 30% chance of MVFR vsbys due to smoke and haze from 05Z-09Z. && .MARINE...04/738 PM. In the Outer Waters, Small Craft Advisory (SCA) level winds will continue over in the southern zones (PZZ673/PZZ676) through Saturday morning. In the northern zone (PZZ670), there is a 50-60% chance of SCA level winds Fri afternoon thru late Fri night, and There is a 50% chance of SCA NW winds Sat afternoon/eve. SCA conds are then not expected later Sat night thru Tue night. For the Inner Waters north of Pt. Sal, there is a 40%-50% chance of SCA winds Fri afternoon/eve. For the Inner Waters south of Pt. Conception, SCA winds are likely during the late afternoon thru late night hours Fri in western portions of the Santa Barbara Channel. The area with the greatest threat of SCA level winds is from Santa Cruz Island to the SBA County south coast from Pt. Conception to Gaviota to Refugio State Beach. Otherwise, conds will be below SCA levels for the southern inner waters through Tue night. Areas of dense fog are expected to affect the coastal waters again tonight into Fri morning. Please reference the Marine Weather Statement for additional information. && .BEACHES...04/128 PM. A southerly swell will affect the Southern California coastal waters into Friday, followed by 15-17-second southerly swell persisting 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 through the weekend to address these concerns. && .FIRE WEATHER...04/136 PM. A dangerous fire weather scenario exists through Saturday. The current heat wave is resulting in an unprecedented stretch of extremely hot conditions with rapidly drying fuels. Humidities over the interior areas will fall into the 5 to 10 percent range by Friday with poor overnight recoveries. Coastal valley areas will also see humidities drop into the teens by Friday. Meanwhile, northwest to northeast winds will gust between 20 to 40 mph through Friday Night over southern Santa Barbara County, many mountains, and the interior valleys like the Antelope Valley. While classic Red Flag thresholds will likely not be met, considering the extreme nature of this event and the holiday fire ignition sources available, conditions are favorable for critical fire weather activity and behavior. That is why Red Flag Warnings have been issued. There is a high risk for grass fires and plume dominated wildfires. The public needs to be urged to refrain with anything that can start a fire, especially in open spaces with dry fuels. Fireworks, campfires, firearms, and dragging tow chains have all started destructive wildfires in the past. Consider the risk for firefighters and neighbors if a fire starts. Residents near large open spaces and the wild land interface should have a plan on what they will do if a wildfire breaks out. Visit readyforwildfire.org and wildfirerisk.org for good resources. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Excessive Heat Warning remains in effect until 6 PM PDT Wednesday for zones 38-343>345-353-376>379-381>383. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 6 PM PDT Monday for zones 88-342-348-351-352-356>358-369>375-380. (See LAXNPWLOX). Heat Advisory remains in effect until 6 PM PDT Sunday for zones 341-347-355-368-548. (See LAXNPWLOX). Excessive Heat Warning remains in effect until 6 PM PDT Saturday for zones 349-350. (See LAXNPWLOX). Beach Hazards Statement in effect through Sunday evening for zones 354-362-366. (See LAXCFWLOX). Red Flag Warning in effect from 10 AM Friday to 6 AM PDT Saturday for zones 342>345. (See LAXRFWLOX). Red Flag Warning in effect until 6 AM PDT Saturday for zones 349-351>353-376>378-381. (See LAXRFWLOX). PZ...Small Craft Advisory in effect until 2 AM PDT Friday for zone 650. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM Friday to 3 AM PDT Saturday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect until 9 AM PDT Saturday for zones 673-676. (See LAXMWWLOX). && $$ PUBLIC...Phillips/MW AVIATION...Phillips/Sirard MARINE...Sirard/Smith BEACHES...Cohen/Sirard FIRE...Kittell SYNOPSIS...MW/KL/CS weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox