FXUS66 KLOX 150347 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 847 PM PDT Mon Oct 14 2024 .SYNOPSIS...14/553 PM. Little change in weather through Tuesday. An upper level low will move over the western United States Wednesday through Thursday, bringing widespread cooling and possible drizzle, with moderate to locally strong northwest to north winds. Weak to moderate north to northeast winds will bring warming and drying to the coastal and valley areas Friday through the weekend. && .SHORT TERM (MON-THU)...14/846 PM. ***UPDATE*** High temperatures today were pretty similar to yesterday's with 70s to low 80s common throughout the region. The interior reached the mid to upper 80s, but the Central Coast trended cooler (2-5 degrees) where marine layer clouds failed to clear. Clouds and patchy fog were quick to expand over the Central Coast and deep into the coastal valleys this evening. Stratus has also moved into areas south of Point Conception from Santa Barbara into Ventura. The marine layer at LAX this evening is about 1200 feet deep, so expecting to see clouds push deep into the valleys, possibly reaching the Santa Clarita Valley by Tuesday morning. Heights begin to fall Tuesday as a weak front approaches, expected to move through the region late Wednesday. This will further deepen the marine layer and lead to temperatures trending 3 to 7 degrees cooler by Wednesday. There is also a slight chance for light rain as the front passes through. North to northwest winds pick up Wednesday afternoon, especially along the Central Coast, the I-5 corridor, the western Santa Ynez range and into the Antelope Valley. Will need to monitor for potential wind advisories for late Wednesday into Thursday. Current forecast looks on track, with minor chances made to the stratus and fog forecast. ***From Previous Discussion*** Tuesday will be very similar weather-wise thanks to a ridge of high pressure hanging out over the region and little change with onshore flow. High temperatures will range between 78 and 88 across the mountains and interior valleys (4 to 8 degrees above normal for this time of year), with coasts and coastal valleys ranging in the 70s to 80s (3 to 8 degrees below normal). Marine layer clouds remained hugging the majority of the coasts so far today, except for along L.A. County coasts, where the Catalina Eddy shifted more west and pulled clouds away from the coast. However, a swift return of low clouds is expected early this evening, and like last night, expected to expand across the coastal valleys overnight. Along the Central Coast, patchy fog and extremely light drizzle is not out of the question overnight into early Tuesday, while the patchy fog will remain limited to the foothill areas south of Point Conception. Northwest to north wind gusts of 20 to 35 mph will continue each afternoon across the Antelope Valley and San Gabriel Mountains each afternoon through Wednesday. The upper level ridge will start to break down Tuesday night, and a trough (associated with an upper level low pressure system moving southeast from Alaska) will start to move across the area. This trough will result in a drop of 500 mb heights by about 10 dam Tuesday night through Thursday. A frontal system associated with this trough will move southward on Wednesday morning, moving across SLO County and the Central Coast, fizzling out by the time it reaches Point Conception. Only a slight chance of light rain showers are expected across that area, with accumulations around a couple hundredths of an inch at most. South of Point Conception, the deepening marine layer (due to decreasing 500 mb heights) will bring the potential for patchy drizzle and fog across the Coasts, coastal valleys, and foothills during the night into morning hours Tuesday night through Thursday morning. Further deepening of the marine layer on Thursday night will result in a slight chance of rain showers across Central and Eastern Los Angeles County, though accumulations are currently forecast to be a couple hundredths of an inch at most. Temperatures will drop temperatures pretty quickly both Wednesday and Thursday. By Thursday, high temperatures will be in the 60s and 70s across the region (ranging from 5 to 15 degrees below normal). .LONG TERM (FRI-MON)...14/248 PM. While the deterministic models and ensembles are starting to come further into agreement each run, there is still some uncertainty in the track of the aforementioned deep low pressure system as it moves southeastward. However, confidence is increasing in the potential for an impactful inside slider to bring gusty winds to the area. Models are showing a 120+ knot jet providing plenty of upper level support for winds Thursday and peaking on Friday. As a result, the most likely outcome is north to northwest wind gusts between 30 and 50 mph common over much of the area. Localized gusts between 55 and 65 mph are becoming more likely with these latest projections over the most favored mountains and foothills including southern Santa Barbara County, the I-5 Corridor, and the Antelope Valley. Winds this strong are capable to producing isolated damage like downed power lines and trees, as well as hazardous driving and boating conditions. The EPS ensembles have sharply trended towards the more wind favorable GEFS projections from the last few days. As such, Friday and Saturday are trending towards gusts between 25 and 40 mph, with isolated gusts to 50 mph over the wind favored areas like western Los Angeles County, north and central Ventura County, and the mountains of Santa Barbara and San Luis Obispo Counties. With the 120+ knot jet in the neighborhood however, there is a range of outcomes plus or minus 10-15 mph. Temperatures over the interior will remain cool with the northeast winds, but coastal and valley areas will warm up. && .AVIATION...15/0053Z. At 2115Z at KLAX, the marine layer was around 1200 ft deep, with a inversion top at 3800 ft and a temperature of 18 C. High confidence in TAFs for KPMD and KWJF. Low to moderate confidence in all other TAFs. Arrival of cigs this evening may be off by +/- 2 hours, and flight cats may be off by 1 category at times. For KSMX and KSBP there is a 20-30% chance of periods of 1/4SM-1/2SM VSBY overnight. South of Point Conception, CIGs are likely to be IFR to MVFR for KSBA, and MVFR with a 20-30% chance of IFR at times. KLAX...Moderate confidence in the 00Z TAF. The return of cigs tonight may be delayed by 2-3 hours and there is a 20% chance of brief or periodic IFR conds overnight. There is a 15% chance of the east wind component reaching 6 kt from 09Z-17Z Tuesday. KBUR...Low confidence in the 00Z TAF. Timing of the return of cigs this evening may be off by +/- 3 hours, and flight cats may be off by 1 category at times. There is a 10-20% chance of LIFR conds overnight. && .MARINE...14/814 PM. Across the outer waters, at least Small Craft Advisory (SCA) level conditions are expected much of the time through Fri night. Lulls in the winds will be possible Tue and Wed morning, especially for the southern waters. By Wed evening there is a 20-30% chance of Gale Force winds for the northern waters, followed by a 50-70% chance of Gales for all the outer waters Thu morning through Fri night. The highest winds speeds are expected Thu evening/night. Seas of 10 to 15 feet are expected Thu and Fri. Nearshore along the Central Coast, SCA conditions are likely through late tonight for seas, then during the afternoon/evening hours Tue through Wed (60-70% chance) and then continually Thu afternoon through Fri night. There is a 20% chance of Gale Force winds Wed evening and a 40-50% chance Thursday evening. Seas 10 to 15 feet possible Thursday and Friday for the western portion. Across the Santa Barbara Channel, there is a 30% chance of SCA level winds across the western/southern portions of the Channel Tue during the afternoon/evening hours, and a 50% chance on Wed during the same time period. SCA winds will be likely (50-70% chance) Thu through Fri, with a 30% chance of Gales Thu afternoon. Seas are likely to peak around 7 to 12 feet across the channel Thursday and Friday. For the nearshore waters off the Los Angeles and Orange County coasts, high confidence in winds and seas staying under SCA levels through Thu morning. Thu afternoon through Fri is a 40-50% chance of NW-N SCA winds and steep seas. Fri night into Sat morning, winds will shift to the NE, with a 30% chance of reaching widespread SCA level. Seas of 6 to 10 feet will be possible Thursday night into Friday. && .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 9 AM PDT Thursday for zones 670-673. (See LAXMWWLOX). Gale Watch in effect from Thursday morning through late Friday night for zones 670-673-676. (See LAXMWWLOX). Small Craft Advisory in effect until 3 AM PDT Tuesday for zone 676. (See LAXMWWLOX). && $$ PUBLIC...Phillips/Lund AVIATION...Smith MARINE...Lewis/Schoenfeld/Smith SYNOPSIS...RK/Smith weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox