FXUS66 KLOX 120003 AFDLOX Area Forecast Discussion...UPDATED National Weather Service Los Angeles/Oxnard CA 503 PM PDT Fri Apr 11 2025 .SYNOPSIS...11/1236 PM. After another warm day today, a cooling trend will establish over the weekend and into early next week as onshore flow strengthens. Night through morning low clouds will become a staple of the forecast over the weekend, pushing into the valleys by early next week and into coastal slopes by mid week. && .SHORT TERM (TDY-MON)...11/213 PM. Fairly benign weather on tap as we move forward into the weekend. Temperatures today will continue to be in the 70s to 80s across the majority of the region, with a few locations pushing into the low 90s. Increasing onshore flow today and decreasing 500 mb heights will help establish a cooling trend into this weekend, with high temps falling by up to 8 degrees Saturday compared to today, and Sunday high temps falling a few degrees more. Temperatures will be generally in the 60s at the coast, and 70s to 80s away from the beaches, which is still 5 to 10 degrees above normal for this time of year (except towards the coast where temps will be near normal). A little bit of uncertainty with the marine layer clouds tonight and into the weekend. While the forecast leans toward the HREF and NAM, with low clouds and fog becoming more expansive over the weekend thanks to the increasing onshore flow, other model guidance suggests low clouds, if any, stick to the immediate coasts of the Central Coast and L.A. County coasts. As low clouds are pushing into the Santa Monica Basin as of now, and a decent eddy has formed, decided to stick with the more expansive marine layer clouds. As 500 mb heights continue to decrease over the weekend ahead of a trough moving over the area, low clouds and fog are likely to push into the coastal valleys by Saturday night. The onshore flow will lead to clouds struggling to clear from the beaches during the morning hours, and may continue to hug the beaches through the day. Besides the low cloud and fog potential, some higher level clouds are expected to stream over the region at times through the weekend, mainly today and Saturday. .LONG TERM (TUE-FRI)...11/212 PM. Cooler temperatures are still favored for next week, especially compared to these past few days as a series of cutoff upper level troughs will move over the region through the week. As of now, deterministic models and ensembles are leaning toward very minimal precipitation for these systems moving through. For the first system, the forceast leans towards a deeper marine layer with cooler temperatures, however some light night through morning drizzle or mountain showers cannot be ruled out. Between the deterministic runs of the GFS and the first few hours of the system with the NAM, the placement of this system shows upper level diffluence over the area, some localized vorticity lobes, and some higher level moisture. In other words, this system has some instability and has about a 5 percent chance of bringing isolated thunderstorms (dry lightning) and showers to the mountains sometime Monday into Monday night. However, this outcome heavily relies on the timing and exact track of the system, so these shower chances could increase, or decrease, as we get closer to Monday. Looking at the next event, there continues to be differences in the deterministic runs for when a cutoff upper level low pressure system will move into the region. The Long Range Ensemble Forecast (LREF) clusters favor the cutoff trough, but potentially strong enough to bring some showers (and rain totals less than 0.5 inches) to the region. While the EC deterministic run is showing potential for showers, only about 20 percent of its ensemble members show any rain, and even then the timing of each is scattered from as early as Wednesday night to as late as over the following weekend. The GFS deterministic, on the other hand, leans toward no precipitation, however its ensembles are similar to the EC's. Regardless, a much cooler airmass will move over the region, and periods of high clouds will be possible along with the troughs. Some rain may be possible across the region toward the latter half of the week, but as of right now, is leaning toward lesser totals (under an inch). Forecast values go with NBM solutions for now. && .AVIATION...12/0002Z. At 2228Z at KLAX, the marine layer was around 400 feet deep. The top of the inversion was near 1700 ft with a temp of 23 C. Overall, moderate confidence in 00Z TAF Package. High confidence in VFR conds for desert airfields (KPMD, KWJF) thru fcst pd. There is a 15% chance of VLIFR to LIFR conds at KBUR and KVNY from 10Z to 16Z Sat. There is a 30% chance of LIFR conds at KSMX from 08Z to 15Z Sat. There is a 30% chance of LIFR/IFR cig arrival at KSBA from 12Z to 18Z Sat. There is a 30% chance of LIFR conds at KOXR from 10Z to 17Z Sat - lower chances (10-20%) at KCMA. 30% chance of LIFR conds at KSMO and slightly higher at KLGB. Timing of cig/vsby restrictions may be off +/- 3 hours. Flight cats may be off one or two. KLAX...Moderate to low confidence in 00Z TAF. Arrival and departure of cigs may be off by a couple of hours. There is a 30% chance of LIFR conds (<3SM,