Area Forecast Discussion
Issued by NWS Los Angeles, CA
Issued by NWS Los Angeles, CA
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096 FXUS66 KLOX 140135 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 635 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)...13/242 PM. 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...14/0134Z. At 2359Z at KLAX, the marine layer was 700 ft deep. The top of the inversion was at about 2500 ft with a temperature of 25 C. High confidence in CAVU TAFs for KPRB, KBUR, KVNY, KPMD, and KWJF. Moderate to low confidence in coastal TAFs. Timing of cat changes may be off by +/- 2 hours from current fcst. There is a 20-30% chance of IFR conditions after cigs arrive. VFR conditions expected at these sites by 17Z. There is a chance that KSBA (40%), KOXR (20%), and KCMA (40%) site will remain VFR through the period. KLAX...Moderate confidence in TAF. Timing of cat changes may be off by +/- 2 hours from current fcst. There is a 30% chance of cigs lower than 005 at any point between 09Z and 13Z. 20% chance of VFR conditions before 17Z. No significant east wind component expected. KBUR...High confidence in CAVU TAF. && .MARINE...13/234 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 20-30% chance of low end gale force wind gusts in the afternoon thru late night hours Wednesday thru Friday, 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) in the afternoon through evening hours through tomorrow night. There is a 50-60% chance of SCA level winds and seas in the afternoon thru evening hours Thursday and 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 until 9 PM PDT this evening 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...Schoenfeld AVIATION...Phillips MARINE...Lewis/Lund SYNOPSIS...KL/Schoenfeld weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox