Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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624 FXUS66 KLOX 311609 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 909 AM PDT Fri May 31 2024 .SYNOPSIS...31/903 AM. A cooler than normal weather pattern will continue across much of the area through the weekend as a persistent marine layer remains in place with strong onshore flow. A warming trend is expected next week, especially for the interior portions of the area Wednesday and Thursday as onshore flow weakens. && .SHORT TERM (TDY-SUN)...31/908 AM. ***UPDATE*** The marine layer has deepened by around 500 feet compared to yesterday and clouds have responded by pushing farther inland and higher up the coastal mountain slopes. Onshore gradients are stronger as well so all signs are pointing towards a cooler day for coast and coastal valleys with slower (if any) clearing of low clouds. Farther inland across the mountains and interior areas it will sunny and warm with highs in the upper 80s to mid 90s with some breezy late afternoon winds. ***From Previous Discussion*** The latest local 3-km WRF time height sections suggest the marine layer deepening additionally tonight into Saturday morning, and Saturday night into Sunday morning as broader troughing aloft will reinforce strong onshore flow. As the latest model solutions have not handled the modeling of the marine layer depth well, the forecast trends a little more aggressive with the low cloud field over the coming days. Weak omega values in the mixed layer in the latest 3-km local WRF solutions suggest the threat of drizzle could be higher over the next couple of mornings, but high- resolution multi-model ensemble solutions downplay the drizzle threat to some extent. Considering there are a few locales with drizzle this morning, the forecast may need to lean more toward the deterministic solution of the local 3-km WRF. Future shifts may need to add drizzle mentions to the forecast for Saturday morning and again for Sunday morning if this signature continues into the coming model runs. With strong onshore flow in place and strengthening additionally today, a cooling trend will develop through the weekend as clouds will struggle to clear from the land mass each day. The forecast goes with clouds hugging the beaches and immediate coast each day, but with KLAX-KDAG surface pressure gradients progged to approach 8 mb onshore, there is a moderate chance that clouds may linger longer across some interior coast and valleys today. Marginally gusty winds will develop across the interior valleys, such as the Antelope Valley and adjacent foothills each afternoon and evening. The latest forecast guidance suggest winds increasing to near advisory levels, but the forecast holds off on issuing any advisories at this point to wait for more data. The latest NAM-WRF solutions trend closer to advisory level winds developing across the Antelope Valley foothills on Saturday afternoon and evening, but the latest forecast ensemble members still lean toward the winds being more on the marginal side. .LONG TERM (MON-THU)...31/450 AM. A warming trend will establish on Monday as high pressure aloft starts to build in over the region. A developing northerly surface pressure gradient will develop gusty northerly winds, most likely affecting the Interstate 5 Corridor on Monday night into Tuesday. EPS solutions bring wind gust means to near 50 mph at KSDB, likely producing the strongest winds at sites like Whitaker Peak and Poppy Park. Gusty Sundowner winds cannot be ruled out either as pattern recognition in some of the deterministic solutions suggest a wind event could develop across southern Santa Barbara County. EPS ensemble members continue to suggest a warming trend turning more significant for Wednesday and Thursday as a cutoff upper- level trough sits south of the border off the Baja California coast and ridging aloft noses into southeast California. Confidence is high for a hot weather pattern developing away from the coast but lower for the coastal areas due to the persistence of onshore flow. NBM solutions give about an 80 percent chance of KPMD and KWJF hitting 100 degrees for the first time this year. Temperatures break away from NBM solutions, going warmer for the middle portion of next week across the interior portions of the area. && .AVIATION...31/1150Z. At 11Z at KLAX, the marine layer was 2000 ft deep. The top of the inversion was at 3500 feet with a temperature of 20C. Low clouds and fog in all coastal and valley areas, with the exception of the interior valleys of SLO County and the Cuyama Valley. Low clouds will likely reach the lower coastal slopes in L.A. and VTU Counties. Conds were mostly IFR to LIFR, with some VLIFR conds (especially in the valleys/foothills and n of Pt Conception). Expect fairly slow clearing today, with cigs scattering out by late morning in the valleys and early afternoon across the coastal plain. Clouds will likely linger at the beaches thru the day, especially S of Pt. Conception, but conds should rise to MVFR levels. Low clouds and fog at the beaches early this evening will spread inland, reaching the valleys and coastal slopes overnight. Low clouds may push into the valleys of SLO County tonight, but are unlikely to reach the Cuyama Valley. KLAX...Moderate confidence in the 12Z TAF. There is a 20% chance that IFR cigs will linger until as late as 17Z-18Z. There is a 20-30% chance that cigs will scatter out between 20Z today and 02Z Sat. There is a 30% chance that cigs tonight will be MVFR rather than IFR. No significant east wind expected. KBUR...Moderate confidence in the 12Z TAF. There is a 30% chance that cigs will linger thru 21Z or 22Z. There is a 20% chance that cigs will arrive as early as 04Z Sat. && .MARINE...31/849 AM. In the northern outer waters zone (PZZ670), winds and seas are expected to reach Small Craft Advisory (SCA) levels (80% chance) this afternoon thru early Sat afternoon. Elsewhere in the outer waters, winds and seas are expected to remain below SCA levels thru early Sat afternoon, with just a 20% chance of SCA level gusts in the central zone (PZZ673) this afternoon and evening. There is a 50% chance of gales in the northern zones (PZZ670/673) Sat afternoon thru Sun night. A Gale Watch has been issued. SCA level winds are likely (70% chance) in the southern zone (PZZ676) Sat afternoon thru Sun night, with just a 20% chance of gales. SCA conds are likely (70% chance) in the outer waters Mon-Tue. In the inner waters N of Pt. Sal, there is a 30% chance of SCA level winds this afternoon/evening. SCA conds are likely (60-70% chance) during the afternoon/eve hours Sat thru Mon. In the inner waters S of Pt. Sal, there is a 40% chance of SCA winds in western portion of the SBA Channel Sat afternoon/eve. SCA level winds are likely there (60-70% chance) Sun afternoon/eve. Otherwise, SCA conds are not expected. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect from 3 PM this afternoon to 3 PM PDT Saturday for zone 670. (See LAXMWWLOX). Gale Watch in effect from Saturday afternoon through late Sunday night for zones 670-673. (See LAXMWWLOX). && $$ PUBLIC...MW/Hall AVIATION...DB MARINE...DB/Sirard SYNOPSIS...Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox