Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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195 FXUS66 KLOX 031620 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 920 AM PDT Fri May 3 2024 .SYNOPSIS...03/909 AM. A cooling trend will begin today with a deepening marine layer through the weekend. A storm system will brush the area to the north this weekend with a chance for light precipitation later Saturday into Sunday. Night and morning low clouds and fog will struggle to clear at the coast today, then spread back inland tonight. A warming and drying trend will develop next week. && .SHORT TERM (TDY-SUN)...03/919 AM. ***UPDATE*** The marine layer has deepened to around 3500 feet across the LA Basin, sloping down to around 1000 feet along the Central Coast. The eddy is a little weaker than yesterday but onshore flow is stronger and it will take longer to clear the stratus today and through the weekend. Still looks like a high chance of rain along the Central Coast Saturday afternoon (around a quarter inch) as a late season storm moves into northern California, but mostly just brushes by our area. Farther south, rain chances will be Saturday night into early Sunday and lighter, mostly under a tenth of an inch. And like this morning some areas will see morning drizzle both Saturday and Sunday. With the storm exiting to the east Sunday and the flow shifting to the west/northwest there should be much better clearing in most areas. ***From Previous Discussion*** The storm system, over the Gulf of Alaska this morning, will dig south into northern California through Saturday night, brushing the area to the north. A cold frontal boundary will drop south into the region on Saturday, bringing rain to much of the area. PoPs have been nudged higher in the latest forecast, going higher than NBM solutions. All of the ensemble members have light precipitation developing for areas north of Point Conception, along the northern slopes of the mountains, and across eastern Los Angeles County. The forecast is little more questionable for southern Santa Barbara County, Ventura County, and western Los Angeles County. The forecast trends wetter as deterministic solutions are starting to trend more southwest to west with the low-level flow pattern. The forecast trends more toward the deterministic solutions south of Point Conception, buying into the model trends. Model tabular forecast output suggests a high- to- likely chance of rain for areas north of Point Conception, and moderate-to-high chance for areas southwest of Point Conception. There is a moderate chance that southern Santa Barbara County, Ventura County, and western Los Angeles County could end up being in a rain shadow effect as downsloping occurs from the Transverse Ranges. Rainfall amounts will likely range from a quarter inch or less, except a quarter to half inch across northwestern San Luis Obispo County. Amounts will be highest for the northern portion of the area and along the northern slopes of the mountains. Rainfall will only amount to a few hundredths at most for most coastal and valley areas south of Point Conception. Gusty west to northwest winds will develop across many coastal areas, into the Santa Ynez Valley, across southern Santa Barbara, up into the Interstate 5 Corridor, and down into the Antelope Valley. EPS solutions indicate good agreement across the area for the potential for wind advisory, but a handful of solutions indicate a gust potential over 55 mph at KSDB. This will need to be monitored as we get closer as wind gusts have been trending generally higher with each run. A colder air mass will spread into the area between Saturday and Sunday night with the cold front. Temperatures during this stretch trend colder than NBM values, and Sunday could be a cold day for May, similar to a February or March with 60s being common across the coastal and valley areas. .LONG TERM (MON-THU)...03/415 AM. A warming and drying trend will develop for the work week next week as high pressure aloft reestablishes. The forecast ensembles agree with a warming trend extending through at least Thursday. EPS solutions tend to hold onto the warming trend extending into next weekend. EPS cloud cover means point to the marine layer depth being kept in check, but confidence is moderate at best in this solution as we are in May. The latest forecast keeps some marine layer induced low clouds and clouds returning to coastal areas by mid week. && .AVIATION...03/1313Z. At 12Z at KLAX, the marine layer was 2800 ft deep with an inversion top at 4500 ft and a temperature of 14 C. Low clouds and fog were widespread in all coastal and valley areas, with clouds moving into the lower coastal slopes. Cigs were mostly high IFR to low MVFR, except LIFR to VLIFR north of Pt Conception, and in the valleys and foothills. Skies should clear by mid to late morning in the valleys and by noon on the coastal plain, but may linger all day at some beaches. Expect similar conditions tonight, with widespread low clouds in coastal and most valley areas, and low MVFR to high IFR conds, except LIFR to VLIFR conds in the foothills. KLAX...Low to moderate confidence in the 12Z TAF. There is a 30-40% chance that cigs will not scatter out at all today. There is a 20% chance of an E wind component of 7-8 kt thru 17Z and from 09Z-15Z Sat. KBUR...Low to moderate confidence in the 12Z TAF. There is a 30% chance of cigs lingering until 20-21Z. There is a 30% chance of cigs will arrive as early as 03Z tonight. && .MARINE...03/723 AM. For the Outer Waters, Small Craft Advisory (SCA) level winds are expected to increase to Gales (70% chance) this afternoon, with the strongest winds off the coast. Gales will continue thru late tonight, then drop to SCA levels. Winds may even drop below SCA level for a while Sat morning, but seas will remain above SCA levels. SCA level winds are expected (80% chance) Sat afternoon, then continue much of the time thru Tue. There is a 50% chance of Gale force winds Sun afternoon/evening, then a 30-40% chance during the afternoon/eve hours Mon thru Tue. For the Inner Waters north of Point Sal, SCA level winds will develop today, then continue thru late tonight. There is a 40-50% chance of SCA level winds/seas during the afternoon/eve hours Sat, then SCA winds are likely (70% chance) during the afternoon/eve hours Sun thru Tue. There is a 30% chance of gales Sun afternoon/eve. For the Santa Barbara Channel, there is a 40% chance of SCA level winds in western portions of the channel this afternoon thru late tonight, then Sat afternoon/eve. SCA level W-NW winds are expected Sat night thru late Sun night (80% chance), and are likely (60-70% chance) during the late afternoon thru late night hours Mon thru Tue. There is a 30% chance of gales Sun afternoon/eve. For the Southern Inner Waters, there is a 30% chance of SCA level winds from Anacapa Island to Malibu during the late afternoon/eve hours Sat. SCA level winds are likely (70% chance) Sat night thru late Sun night. There is a 40% chance of SCA level winds during the late afternoon thru late evening hours Mon thru Tue. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 3 AM PDT Saturday for zone 645. (See LAXMWWLOX). Gale Warning in effect until 3 AM PDT Saturday for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...MW/Hall AVIATION...DB MARINE...DB/RAT SYNOPSIS...MW/Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox