Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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516 FXUS66 KLOX 050334 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 834 PM PDT Tue Jun 4 2024 .SYNOPSIS...04/818 PM. High pressure aloft over the region will continue a warming trend through Wednesday, most pronounced away from the coast. High pressure aloft will thin the marine layer depth some and keep clouds confined to coastal and valley areas. A hot air mass will remain in place across the interior valleys for much of this week, with temperatures well above normal for this time of year. Closer to the coast, the warming trend will be moderated due to persistent night through morning low clouds and fog and a moderate to strong onshore flow. && .SHORT TERM (TUE-FRI)...04/833 PM. ***UPDATE*** The predicted warming trend has arrived and it will really kick into gear Wednesday across the far interior areas that are well removed from the cooling effects of the Pacific Ocean. Onshore flow continues to weaken but there will be enough of it to keep coast and coastal valleys from warming up too much. However, interior valleys like the Antelope Valley, interior SLO, and the Cuyama Valley will be warming up to the high 90s to around 105. The 00z NAM shows 950mb and 850mb temperatures dropping 1-3 degrees Thursday, which combined with a 1.5mb onshore trend should bring temperatures down slightly at least for coastal valleys. Less confidence that the cooling will reach the interior valleys, though most of the numerical guidance are leaning this way. ***From Previous Discussion*** No significant changes to the forecast. Heat Advisories were added for the I-14/Acton area of the LA mountains and Cuyama Valley Wednesday and Thursday, complementing the already issued Heat Advisory for interior San Luis Obispo County including the Paso Robles area and the Excessive Heat Warning for the Antelope Valley. The heat can have significant impacts on anyone, but sensitive groups like the very young or old and those with prolonged exposure outside are particularly vulnerable to heat impacts. If possible, take steps to limit exposure from the heat by taking breaks inside with air conditioning or by finding shade and also drinking plenty of water. High confidence in a warming trend focused across Coastal Valleys to interior through Wednesday as a strong (for early in the season) ridge of high pressure builds into the region. The marine layer will continue to shelter coastal areas from much of the warming compared to interior areas. It will also continue to provide night to morning low clouds with dense fog becoming more Low confidence in the extent of the marine layer especially into Tuesday due to competing forces between the building ridge pressing down on the marine layer and the potential for a Catalina Eddy acting to prop it up. This leaves us with only moderate confidence in daytime highs across coastal valleys in particular. If marine influence is less than anticipated, Heat Advisories may need to be expanded to a few inland coastal valleys. We continue to advertise daytime highs of 98-108 for interior areas, 85-95 coastal valleys, and 70-85 coastal areas. Guidance has slowed with the breakdown and eastward progression of the ridge, so the cool down may be slow enough to maintain heat impacts through Friday with some potential for some of the heat products to be extended through then. There is just enough mid level moisture arriving from the south to warrant around a 10 percent chance of showers or thunderstorms focused across the higher mountains in Los Angeles, Ventura, and perhaps Santa Barbara County as early as Thursday. .LONG TERM (SAT-TUE)...04/240 PM. Lower confidence in the forecast next weekend the details related to the ridge breaking down remains elusive. There is a 10 percent chance (leaving a 90 percent chance that unremarkable early June weather continues) a baggy trough setting up will be favorable for showers or thunderstorms for interior areas and drizzle or light showers for closer to the coast. Either way temperatures should cool at least somewhat, possibly significantly for interior areas should the more active weather scenario play out. && .AVIATION...04/2301Z. At 22Z at KLAX, the marine layer was 1200 ft deep. The top of the inversion was at 4000 feet with a temperature of 26 Celsius. High confidence in timing of cloud arrival and coverage of low clouds tonight expected to be later and less than yesterday. Ceilings and visibility likely to be lower as well. Clearing on Wednesday will likely be poorer or later for coastal airports and similar or better for valley sites. KLAX...Clouds will return as early as as 02Z and as late as 06Z. Ceilings should be OVC008-012. There is a 30 percent chance of BKN004-006 09-15Z. Clearing on Wednesday will be as early as 17Z and as late as 20Z. High confidence in any east winds staying well below 08 knots. KBUR...There is a 50% chance of ceilings forming again tonight, as early as 09Z and as late as 13Z. If ceilings form, expect 1-3SM BKN003-006 common. && .MARINE...04/830 PM. Gusty northwest winds will remain over the offshore waters off the Central Coast, but will be less expansive. There is a 70 percent chance of Gale Force winds this evening beyond 30 miles from the coast including buoy 46028. Otherwise, winds below Small Craft levels will impact the remainder of the waters. These winds will also generate choppy seas over much of the coastal waters. SCA winds are likely through Thursday over the outer waters off the Central Coast. Otherwise, high confidence winds will stay under SCA, although seas near 10 feet are possible beyond around 20 NM from shore. Southeast winds will be prevalent each morning south of Point Conception, which locally could exceed 15 knots near islands and channels. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory remains in effect from 10 AM Wednesday to 8 PM PDT Thursday for zones 38-343-344-379. (See LAXNPWLOX). Excessive Heat Warning remains in effect from 10 AM Wednesday to 8 PM PDT Thursday for zones 381>383. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 9 PM PDT this evening for zones 645-676. (See LAXMWWLOX). Gale Warning in effect until 11 PM PDT this evening for zones 670-673. (See LAXMWWLOX). && $$ PUBLIC...MW/Munroe AVIATION...RK MARINE...Kittell/Smith SYNOPSIS...MW/RM weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox