FXUS66 KLOX 192114 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 214 PM PDT Fri Apr 19 2024 .SYNOPSIS...19/130 PM. Strong onshore flow in place will continue the cooling trend into today. Extensive low clouds and fog will struggle to clear as a deep marine layer depth remains in place into tonight. A warming trend is expected over the weekend as weak high pressure develops. Significant cooling along with a deep marine layer are expected next week as low pressure moves into the area. In addition, there is a slight chance of showers or drizzle late next week. && .SHORT TERM (TDY-MON)...19/202 PM. A weak trough over California has induced a strong onshore flow and deep marine layer that has kept skies cloudy across much of the coast/valley areas through mid-afternoon and temperatures well below normal. Skies have started clearing across LA County and parts of the Central Coast but it remains socked in from Santa Barbara to Thousand Oaks. Pressure gradients are starting to trend weaker this afternoon and the trough that started all this is shifting east so models appear to be on track with the warming trend over the weekend and decreasing stratus. Saturday will be a transition day, still with plenty of marine layer in the morning through the coast and valleys, but likely earlier clearing and warmer temps by afternoon. Sunday is expected to be significantly warmer at least for inland areas where highs in the mid to upper 80s are expected. Most coastal areas will be warmer too but still with the effects of the cool onshore breeze keeping temps on the mild side, but with a degree or two of normal. Monday will begin a long duration cooling trend that will last through the following weekend as a series of low pressure systems hit the West Coast. Still at or above normal in most areas Monday but at least a few degrees cooler than Sunday. .LONG TERM (TUE-FRI)...19/216 PM. A series of troughs will move through the West Coast and California next week keeping temperatures well below normal with moderate to strong onshore flow each day, a solid marine layer with slower than usual clearing, and breezy onshore winds in the mountains and deserts. By Tuesday or Wednesday high temperatures in all areas will in the mid to high 60s at most with chances for morning drizzle each day through the week. The coolest days with the highest chances for either drizzle or light rain will be Thursday and Friday when the deepest trough arrives. Models have bounced around with the trajectory, some showing a wetter and farther west trajectory but more showing a less wet but cooler inside track. 500mb heights drop into the high 550's across the area, and high temps may still be too high in the official forecast as patterns like this often result in mostly low to mid 60s and little if any sunshine across coast/valleys. A lot will depend on the ultimate track of the system and how deep the moisture is. Temps are expected to slowly rebound by next weekend but still likely well below normal through the end of the month. && .AVIATION...19/1554Z. At 15Z over LAX, the marine layer was 2500 feet deep with an inversion top at 5200 feet and 15 degrees Celsius. Moderate to high confidence in generally persistence forecast (similar flight categories and timing for the next 24 hours as the previous). While ceilings will be most common over the next 24 hours, low confidence on timing and coverage of any clearing. KLAX...Moderate confidence in OVC015-025 being most common through Saturday 18Z. Low confidence on when and if clearing will occur today, but the window for that is 20-02Z. 30 percent chance of no clearing in that window, 40 percent chance of 2-4 hours of clearing, and 30 percent chance of 5+ hours of clearing. Southeast winds of 4-6 knots is likely through 19Z today, and 10-18Z Saturday, but the chance of exceeding 8 knots is less than 20 percent. KBUR...Moderate confidence in OVC012-020 being most common through Saturday 18Z. Moderate confidence on 3-6 hours of clearing today in the 19-06Z window, with a 20 percent chance of any clearing lasting less than 3 hours. && .MARINE...19/1054 AM. High confidence in winds staying below 20 knots through Saturday morning, except for winds locally to around 20 knots this evening between Point Conception and Santa Rosa Island. Seas will remain small as well. High confidence in Small Craft Advisory (SCA) winds and choppy seas forming quickly Saturday afternoon for the Central Coast offshore waters down to San Nicolas Island. These winds will persist through the weekend. There is a 40 percent chance of SCA winds for the nearshore Central Coast waters and a 10 percent chance for the western half of the Santa Barbara Channel on Saturday. Those chances increase by 20 percent on Sunday. All areas will see building short period seas from these winds. Winds will weaken Monday and Tuesday, but will stay near SCA south of Point Conception with choppy seas over most areas continuing. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect from 2 PM Saturday to 6 AM PDT Monday for zones 670-673. (See LAXMWWLOX). && $$ PUBLIC...MW AVIATION...Kittell MARINE...RK SYNOPSIS...MW/Hall weather.gov/losangeles Experimental Graphical Hazardous Weather Outlook at: https://www.weather.gov/erh/ghwo?wfo=lox