Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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657 FXUS66 KLOX 060524 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 1024 PM PDT Wed Jun 5 2024 .SYNOPSIS...05/735 PM. High pressure over the region will continue above normal temperatures through Thursday, most pronounced away from the coast. The marine layer will continue to bring some night through morning low clouds to the coastal and valley areas. While very warm temperatures are expected over the interior through Saturday, closer to the coast, highs will be moderated by the marine layer and moderate to strong onshore flow. && .SHORT TERM (WED-SAT)...05/1022 PM. ***UPDATE*** Marine layer clouds made an early return to the coasts this evening under a strong inversion. With heights around 590 to 592 dam, a marine layer depth around 1800 ft and onshore flow with a 6 mb LAX to DAG gradient tonight, expecting low clouds and patchy fog to push through the coastal plains and into the valleys overnight. There is some uncertainty if dense fog will develop near the coasts, may need to add dense fog over the coastal waters for tonight into Thursday morning. Thursday morning, the upper level pattern shows high pressure slowly decreasing as the center of the ridge shifts eastward which will start deepening the marine layer. Skies will struggle to clear at the coasts through the day, especially for west-facing beaches as the afternoon LAX-DAG onshore gradient is expected to trend stronger peaking near 8-9 mb. Clouds and patchy fog will push deeper into the valleys Thursday night, and not seeing an end to marine layer clouds as gradients trend stronger and heights continue to fall. The current forecast looks on track, with only minor changes made to the extent of marine layer clouds and patchy fog. .SHORT TERM (WED-SAT)...05/133 PM. Overall for the short term, 12Z models in good synoptic agreement through the period. At upper levels, ridge will remain over the desert Southwest through Thursday then will shift eastward Friday and Saturday as a trough develops along the West Coast. Near the surface, onshore flow will gradually strengthen through the period. Forecast-wise for the immediate short term, main issue is heat. With upper ridge remaining dominant feature through Thursday, inland heat will continue. Looking at both deterministic and ensemble stuff, heat will continue through Thursday across interior sections with temperatures actually threatening records across the Antelope Valley. So will keep EXCESSIVE HEAT WARNING in effect for the Antelope Valley and HEAT ADVISORIES in effect for interior San Luis Obispo county, the Cuyama Valley and the western range of the San Gabriel Mountains. For areas west of the mountains, a continued marine influence and moderate to strong onshore gradients will keep things cooler. For Friday and Saturday, all areas will experience some slight cooling on Friday and a bit more pronounced cooling on Saturday. Otherwise, no major issues are expected through Saturday. Will expect the marine inversion to gradually deepen each day with better inland penetration each night/morning. Dissipation of stratus each day should be good for all areas but the immediate coast where clouds could remain stubborn each afternoon. Also, 12Z models came in much drier at mid-levels on Thursday, so have knocked down POPs to below mentionable levels for the mountains. As for winds, the moderate to strong onshore gradients will generate gusty southwesterly winds across interior sections, including the Antelope Valley, but any advisory-level winds should remain localized. .LONG TERM (SUN-WED)...05/133 PM. For the extended, 12Z models continue to exhibit decent synoptic agreement. At upper levels, trough will linger along the West Coast through Sunday then will slowly drift southwestward early next week (well offshore) as a ridge builds once again over the desert Southwest. Near the surface, moderate to strong onshore gradients are forecast to continue. Forecast-wise, no significant issues are anticipated through the period. Main "concern" will be the continued presence of the marine layer stratus. Inversion likely to be deepest on Sunday then will shrink slightly early next week. So, low clouds and fog will likely push into the coastal valleys each night with good dissipation each afternoon. Other than the stratus, skies should remain mostly clear through the middle of next week. As for temperatures, Sunday will likely be the coolest day with a slight warming trend for most areas Monday through Wednesday. The onshore gradients will continue to generate gusty southwesterly winds each afternoon across interior sections. && .AVIATION...06/0223Z. At 2355Z at KLAX, the marine layer was 1300 ft deep. The top of the inversion was at 4100 ft with a temperature of 27 Celsius. High confidence in a return of ceilings to coasts and most valley sites. However, lower confidence in cigs at PRB, which will likely be short-lived. IFR to LIFR conditions will be common, with MVFR conditions more likely Thursday morning/afternoon. KLAX...Ceilings quickly returned this evening. Expecting IFR to LIFR conditions overnight, but dense fog is not expected. High confidence in any east winds staying below 8 knots. KBUR...Ceilings will return tonight as early as 05Z and as late as 09Z. Lower confidence in timing of category changes. There is a 10-20% chance for vis down to 2SM around 12Z. && .MARINE...05/733 PM. Small Craft Advisory (SCA) winds and seas have ended for the outer waters off the Central Coast. Otherwise, southeast to southwest winds are expected for much of the waters through Thursday. Winds will peak around 15 knots in the afternoon and in the morning between the islands and through any channels. There is a 30% chance of SCA level winds late Sat thru Sun, especially off the Central Coast. Reduced visibilities are expected each morning through at least the weekend, possibly dense each morning and below one mile from Santa Barbara to the Central Coast. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Heat Advisory in effect until 8 PM PDT Thursday for zones 38-343-344-379. (See LAXNPWLOX). Excessive Heat Warning in effect until 8 PM PDT Thursday for zones 381>383. (See LAXNPWLOX). PZ...NONE. && $$ PUBLIC...Thompson AVIATION...Phillips MARINE...Kittell/Smith SYNOPSIS...Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox