FXUS66 KLOX 140611 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 1111 PM PDT Tue Aug 13 2024 .SYNOPSIS...13/201 PM. Temperatures will remain below to near normal though this weekend, with overnight to morning low clouds and fog across coastal areas at times. Over the next few days, gusty winds are likely across the Santa Barbara southwestern coast and the Antelope Valley during the evenings. && .SHORT TERM (TUE-FRI)...13/958 PM. ***UPDATE*** Temperatures trended cooler today (about 2 to 7 degrees of cooling for most of the area) with most areas reaching the 80s to 90s. Coasts were stuck in the 60s to 70s, with especially cool values along the Central Coast due to strong onshore flow and lingering marine layer clouds. Heights are forecast to rise overnight tonight and through Wednesday (peaking near 594 DAM), which should lead to temperatures trending slightly warmer most regions. This slight warming trend should continue into Thursday as high pressure continues to build. Marine layer clouds were limited with very patchy coverage over the area this morning. Most of the clouds were confined to the Central Coast, and from the Ventura Coast southward. It is unclear how much marine layer clouds will redevelop, especially under rising heights and with plenty of dry air aloft that could mix downward. So far, clouds have only developed over coastal areas just north of Point Conception and portions of the immediate LA County coast. Expecting more clouds to develop and move into the Central Coast along with the LA Basin, but low confidence in clouds reaching the Ventura County coast. Sundowner winds have developed over western portions of the Santa Ynez Range with gusts of 30 to 40 mph. Winds should remain below sub-advisory levels tonight. However, Sundowner winds will reoccur each night, with better chances to reach advisory levels Wednesay night and Thursday night. ***From Previous Discussion*** The broad high pressure system centered well southwest of SoCal will begin to build back today and Wednesday. 500 mb heights will rise from 588-590 dam today to 592-595 dam by Wednesday night. Friday, a powerful trough with a low pressure center of around 563 dam will start stalling to the west of Oregon and Washington State. The trough will nudge the previously mentioned high pressure center to the east, bumping it to around Arizona and New Mexico, and heights over SoCal will fall again to around 589-591 dam Friday. The overall temperature pattern will generally a;light with the 500 mb heights, however fluctuations each day will be fairly minimal through Friday. Expect the coolest temperature today, followed by slight warming Wednesday and Thursday, as hieghts rise and onshore flow decreases. Despite a warming trend, even Thursday temperatures will be near normal for much of the region, except for the Santa Barbara South Coast which will see temperatures several degrees above normal. Friday, as heights fall and onshore gradients pick up again, temperatures will drop a couple degrees. Strong north-to-south pressure gradients tomorrow night and Thursday night will drive Sundowner winds across the Santa Barbara South Coast. Across the southwest portion gusts are expected to be 35 to 50 mph, with the eastern Santa Ynez mountains and foothills likely to see gusts 25 to 35 mph. Wind Advisories are likely to be issued for tomorrow evening and Thursday evening for the Southwestern Santa Ynez range and coastline below. Downsloping compressional heating will produce warm temperatures across the whole Santa Barbara South Coast (including Santa Barbara City), with highs several degrees above than normal. Elsewhere, onshore pressure gradients will continue to yield the typical southwesterly to westerly wind gusts during the afternoons and evenings across the Antelope Valley/foothills through the Highway 14 Cooridor, with gusts 20 to 40 mph common. Low clouds and fog will prevail for the beaches during the overnight-to-morning hours. However due to lackluster onshore pressure gradients and high pressure, the inland extend of marine layer clouds is likely to be limited. With one possible exception for the Los Angeles County coastal plains tomorrow night and Thursday night. A high north- to- south pressure gradient for the region signals that a moderate Catalina Eddy may form both nights, lifting the marine layer and increasing low cloud coverage for the Los Angeles Basin. .LONG TERM (SAT-TUE)...13/255 PM. Starting this weekend, there is high confidence that the region will remain under a stagnant pattern. The region will be under the intersection of a trough just west of the Pacific Northwest and high pressure center over the desert southwest. Ensembles indicate some uncertainty in the exact 500 mb heights values as well as the location of the high pressure system. This translates to uncertainty in the precise temperatures each day and chances of monsoonal moisture. Overall temperatures appear to be warmest on Monday and Tuesday. North- to- south pressure gradients indicate that Sundowner winds will continue during the evenings for the Santa Barbara southwest coast. Chances for monsoonal mositure starts to increase starting Saturday. Based on the ensembles, Saturday through Tuesday there is about a 20 to 30 percent chance of monsoonal mositure that would be favorable for thunderstorms. Overall thunderstorm chances remain under 10 percent in the long term. Looking ahead, based on Climate Prediction Center's precipitation outlook, the area southeast of Los Angeles county is leaning above normal for days 8 to 14. This indicates that the slight chance of monsoonal mositure/thunderstorms will continue beyond Tuesday for Los Angeles (and maybe Ventura) county. && .AVIATION...14/0610Z. At 0505Z at KLAX, the marine layer was 700 ft deep. The top of the inversion was at about 2100 ft with a temperature of 25 C. High confidence in CAVU TAFs for KPRB, KBUR, KVNY, KPMD, and KWJF. Moderate confidence in coastal TAFs. There is a 25 percent chc of IFR cigs at sites with no cigs fcst and the same 25 percent chc of no cigs at sites with cigs fcst. If cigs do arrive the timing could be off by +/- 2 hours. KLAX...Moderate confidence in TAF. There is a 25 percent chc of no low clouds. If low clouds do occur they could arrive as early as 09Z or as late as 13Z. No significant east wind component expected. KBUR...High confidence in CAVU TAF. && .MARINE...13/849 PM. For the outer waters, moderate to high confidence in current forecast. Small Craft Advisory (SCA) level winds and seas expected through at least Sunday night. There is a 30-50% chance of low end gale force wind gusts in the afternoon thru late night hours Wednesday thru Friday (with the highest chances on Thursday), and a 10% chance Saturday and Sunday. For the inner waters north of Point Sal, moderate confidence in current forecast. SCA level winds and seas are likely (60-70% chance) much of the time Wednesday afternoon through Thursday night. There is a 50-60% chance of SCA level winds and seas in the afternoon thru evening hours on Friday, and a 30-40% chance Saturday and Sunday Sunday. For the inner waters south of Point Conception, moderate confidence in current forecast. There is a 30-50% chance of SCA level wind gusts for the western Santa Barbara Channel during the afternoon into late evening hours through Thursday, and a 20-30% chance of SCA level winds Saturday and Sunday in the afternoon to evening hours. Otherwise, conds will remain below SCA levels over the southern inner waters through Sunday night. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect from 3 PM Wednesday to 5 AM PDT Friday for zone 645. (See LAXMWWLOX). Small Craft Advisory in effect until 2 PM PDT Thursday for zones 670-673-676. (See LAXMWWLOX). Gale Watch in effect from Thursday afternoon through late Thursday night for zones 670-673-676. (See LAXMWWLOX). && $$ PUBLIC...Phillips/Schoenfeld AVIATION...Rorke MARINE...Lewis/Schoenfeld SYNOPSIS...KL/Schoenfeld weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox