481 FXUS66 KLOX 290001 AFDLOX Area Forecast Discussion National Weather Service Los Angeles/Oxnard CA 501 PM PDT Sat Sep 28 2019 Updated Aviation Section .SYNOPSIS...28/1234 PM. An unseasonably strong and cold upper level trough draped over the West Coast will bring cooler than normal temperatures through early next week. There is a chance of light rain today especially over Los Angeles County. Gusty northwest winds are likely over the Central Coast and Santa Barbara County south coast this afternoon and evening. A warming trend is expected by Wednesday. && .SHORT TERM (TDY-TUE)...28/156 PM. Deep moist layer persists early this afternoon mainly S of Point Conception and was around 5300 ft deep at LAX. Strong onshore gradients from LAX-DAG was +7.3 mb at 20Z which was helping to produce additional light rain across portions of L.A. County from the coast to the coastal slopes which should continue thru sunset. Further N, skies were slowly clearing out over SLO/SBA Counties as a drier and cool NW flow filters into the area. In addition, a further increase in the onshore flow this afternoon will bring gusty NW winds along the Central Coast into the SBA County S coast and mtns, and gusty W to SW winds for the L.A. County mtns and Antelope Vly. These areas will see wind gusts up to 40 to 50 mph, with Wind Advisories in effect from this afternoon into tonight. Please see the latest Non-precipitation Weather Message (LAXNPWLOX) for further details. Elsewhere, gusty sub-advisory level onshore flow can be expected this afternoon and evening as well. Temps today will be about 5 to 15 deg below normal in all areas, with the warmest coast, vlys and lower mtns reaching only into the lower to mid 70s. A broad and unusually strong (for late September) upper level trough will affect CA tonight into Sun, with little change expected Sun night and Mon. Another piece of energy will move into the upper level trof and dig it further S into srn CA Mon night and Tue. H5 heights over swrn CA will be generally in the 565-573 DM range from N to S tonight thru Tue. There will be a broad and dry W to WSW flow aloft thru Mon night before turning more W to NW on Tue. Mostly cloudy skies with lingering stratus can be expected tonight for the L.A. County coast/vlys and lower coastal slopes before scattering out Sun morning. There may also be some more light rain in spots over the San Gabriel Vly and foothills of the San Gabriel Mtns this evening. Some clouds and light rain or snow will also be possible in the N mtn slopes of VTU County later tonight. Otherwise, mostly clear skies can be expected for much of the region during the period. Mostly clear skies should then prevail in all areas Sun night thru Tue as dry but cool northerly flow pattern persists. Decent N-S gradients will persist across the region Sun through Mon night. There will likely be gusty northwest winds on the Central Coast during the afternoon and evening hours Sunday and again Monday, possibly to advisory levels. Advisory level NW winds are possible across the Santa Ynez Range and the adjacent south coast of SBA County, and the Interstate 5 corridor late Sun into Sun night and again late Mon into Mon night. Temps Sun and Mon are expected to turn slightly warmer but still remain significantly below normal. Highs both days in the warmest coast and vlys should be in the mid to upper 70s. With some offshore flow, Tue should be slightly warmer but still a few degrees below normal with the warmest coast/vlys in the mid 70s to around 80. .LONG TERM (WED-SAT)...28/159 PM. The broad upper level trof over CA is expected to finally move E for Wed with rising H5 heights to 579-581 DM. Another broad upper level trof over the E Pac should move into CA on Thu and Fri before exiting to the E with some upper level ridging building over srn CA on Sat. Gradients are forecast to trend offshore Wed, remain weak Thu and Fri, then could be slightly offshore again on Sat. This should help to keep away marine layer clouds during the period, except there is a small chance for a return to some marine layer clouds for the L.A. County coast and Central Coast by next Sat morning. Overall though, mostly clear skies are expected Wed thru Sat. Temps are forecast to warm to near normal to slightly above normal away from the immediate coast thru the period. Highs in the warmest inland coastal areas, vlys and lower mtns are expected to reach the 80s each day. && .AVIATION...28/2358Z. At 23z at KLAX there was no marine layer or inversion. Gusty winds with mountain waves possible at KWJF KPMD through 06Z. LLWS possible at KSBA 01-08Z, but likely under +/- 20KT. Moderate confidence that all airports currently without CIGS will stay without CIGS through Sunday. There is a 40 percent chance of MVFR CIGS 10-16Z at KPRB, and 20 percent chance at KSBP KSMX. Moderate confidence that airports currently with CIGS will become SCT by 03-06Z, then stay SKC-SCT through Sunday. There is a 20 percent chance of MVFR CIGS 10-16Z at KLAX KLGB KSMO. KLAX...Moderate confidence that MVFR CIGS will continue through at least 02Z, becoming SCT 03-06Z. There is a 20 percent chance of MVFR CIGS 10-16Z. East wind likely 09-16Z, with 20 percent chance of reaching 08KT. KBUR...Moderate confidence that MVFR CIGS will continue through at least 03Z, becoming SCT 04-07Z. Moderate confidence of staying VFR afterwards through Sunday. && .MARINE...28/109 PM. Outer Waters... West to northwest Small Craft Advisory (SCA) level winds will increase rapidly across the northern outer waters and will reach gale force level in the afternoon. Winds across the central and southern outer waters will increase to SCA level by midday and gale force late this afternoon. Winds will weaken across the outer waters through the morning hours but will increase to at least SCA level again in the afternoon and evening hours Sunday through Tuesday. Inner Waters north of Point Sal... Northwest winds will increase to SCA level this afternoon through late tonight. Winds will weaken through the morning hours but will increase to at least SCA level again in the afternoon and evening hours Sunday and Monday. Inner Waters south of Point Conception... Northwest winds will increase to SCA level this afternoon through late tonight. Winds will weaken through the morning hours but there is a seventy percent chance they will increase to at least SCA level again in the afternoon and evening hours Sunday and Monday. There is a sixty percent chance of SCA level winds in the western portion of the Santa Barbara Channel on Tuesday. All coastal waters will have very choppy and building seas by this evening. Similar but slightly weaker conditions will occur on Sunday and Monday, except with the focus shifting from off the Central Coast down to Point Conception and the Channel Islands. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...Wind Advisory in effect until 9 PM PDT this evening for zones 34-35-54-59. (See LAXNPWLOX). Wind Advisory in effect until 3 AM PDT Sunday for zones 39-52. (See LAXNPWLOX). PZ...Small Craft Advisory in effect until 3 AM PDT Sunday for zones 645-650-655. (See LAXMWWLOX). Gale Warning in effect until 3 AM PDT Sunday for zones 670-673-676. (See LAXMWWLOX). Small Craft Advisory in effect until 5 PM PDT this afternoon for zones 673-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK (TUE-SAT). No significant hazards expected. && $$ PUBLIC...Sirard AVIATION...Kittell MARINE...Kj SYNOPSIS...Stewart weather.gov/losangeles