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000 FXUS66 KLOX 090316 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 816 PM PDT Thu Jun 8 2023 .SYNOPSIS...08/846 AM. Some warming with a mix of clouds, sun, and mountain thunderstorm threat through Friday. Another low pressure system will bring cooler conditions and another increased threat of widespread showers and thunderstorms over the weekend, potentially similar to earlier this week. Warming to follow Monday through the middle of next week. && .SHORT TERM (THU-SUN)...08/815 PM. ***UPDATE*** Overall, a quiet early evening across the forecast district. Latest satellite and surface observations indicate some patchy low clouds across the area with mostly clear skies elsewhere. Current sounding data indicates marine inversion at a depth in the 1500-2000 foot range. Forecast-wise for the immediate short term, main challenge will be the behavior of the marine layer stratus. The depth of the inversion has decreased, but the inversion still is not too strong. So, overnight, will expect the stratus to behave somewhat chaotically with low confidence in areal coverage. However, all coastal and valley areas will likely have a period of low clouds overnight. Otheriwse, there will be some high clouds drifting overhead. Overall, current forecast has good handle on the immediate short term. So, no significant updates are expected. ***From Previous Discussion*** Continued chaotic cloud pattern today, although clouds are generally clearing away over Ventura and Los Angeles Counties where the marine layer inversion is weakest (now only 1 degree Celsius). To the north over Santa Barbara and San Luis Obispo, the clouds are more persistent with a slightly stronger marine layer inversion keeping the low-level moisture confined to the surface. The inversion should strengthen a little overnight with a weak high pressure ridge forming, but will still be very weak especially over Ventura and Los Angeles Counties. As a result, the low cloud pattern will likely not be very uniform with random areas of clouds and clear skies. There is no great way to code that into the forecast, so had to go with more clouds than will actually materialize. For thunderstorms, clouds are starting to form over the Ventura and San Gabriel Mountains, but they do not look very convective. Still cannot rule out a late-bloomer thunderstorm or two today or tomorrow, but more than likely not much will happen. Temperatures will warm a little more on Friday as that weak upper level ridge forms, but most of that warming will be confined to the mountains and interior valleys or deserts. A budding upper level trough, currently about 1200 miles west of Oregon, will form into a closed low just off the central California coast by late Friday Night. The vast consensus of computer projections and their ensembles move that low right through southern California over the weekend, in a very similar track to the low that came through earlier this week. With enough available moisture (precipitable water 1.0-1.2 inches), expecting most if not all areas to receive measurable rain sometime over the weekend, especially Saturday night. Convective parameters are all really good over the mountains and interior valleys (peak values of -6 lifted index, 41 K-index, 3000 MUCAPE, and 850 millibar dewpoints of 12 degrees C)...with the coastal and valley areas about half of those valleys (which is still really good for those areas). As such, there is a moderate threat for thunderstorms over all areas, along with all the impacts they usually bring (lightning, heavy showers, gusty winds, small hail). Fairly confident of rain and thunderstorms over the most favored areas which includes the mountains and interior valleys over Ventura, Santa Barbara, and San Luis Obispo Counties. Rain totals in those areas will likely fall in the 0.25 to 1.00 inch range, with peak rates of 0.25-0.50 inches per hour (most of which fall in 15 minutes or less). There is a moderate threat of isolated flash flooding of creeks as a result. Far less confidence in the details for all other areas, with highly variable rain amounts and rates, and thunderstorm coverage. .LONG TERM (MON-THU)...08/200 PM. The aforementioned low will move to the east and out of the area by later Monday, but some of the ensemble runs (EPS GEFS CMC) keep the low in the area long enough for some wrap-around moisture to bring additional showers through Monday. After that, conditions look to return closer to normal through most if not all of next week, with low clouds and fog and high temperatures generally in the 70s (expected 80s in the desert). && .AVIATION...08/2347Z. At 2210Z, there was a very weak marine inversion, based around 3000 feet, at KLAX. The top of the inversion was 6200 feet with a temperature of 13 degrees Celsius. Overall, low confidence in 00Z coastal and valley TAFs, but high confidence in desert TAFs. Low confidence in coastal/valley sites is due to extreme uncertainties with possible development of marine layer stratus. Current forecasts call for return of MVFR and IFR CIGs to all sites, but confidence, as well as possible, timing remains low. KLAX...Low confidence in 00Z TAF. Timing of development of MVFR CIGs could be +/- 4 hours of current 09Z forecast. There is a 40% chance that CIGs will not develop. No significant easterly wind component is expected. KBUR...Low confidence in 00Z TAF. Timing of development of MVFR CIGs could be +/- 4 hours of current 11Z forecast. There is a 40% chance that CIGs will not develop. && .MARINE...08/754 PM. For the Outer Waters, high confidence in current forecast as winds and seas are generally expected to remain below Small Craft Advisory (SCA) levels through Tuesday. However, there is a 30% chance of SCA level winds Saturday afternoon and night. For the Inner Waters north of Point Sal and south of Point Conception, high confidence in current forecast. Winds and seas are generally expected to remain below SCA levels through Tuesday. However, there is a 20% chance of SCA level winds Saturday afternoon and night. There is a slight chance of thunderstorms across the coastal waters Saturday through Sunday. Any thunderstorms that develop would be capable of producing brief heavy rain, gusty winds, small hail and dangerous cloud to surface lightning. Also, waterspouts could be possible. && .BEACHES...08/921 AM. Surf of 3 to 5 feet is expected on south facing beaches of L.A. and Ventura Counties, with locally higher sets to 6 feet on some beaches. There will be a high risk of rip currents. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && $$ PUBLIC...Kittell AVIATION...RAT MARINE...RAT BEACHES...Sweet/Smith SYNOPSIS...Hall/RK weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox