Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/21/20

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
903 PM PDT Sat Jun 20 2020 .SYNOPSIS...20/643 PM. Night to morning low clouds and fog will affect the coast and some of the coastal valleys tonight through next Saturday. Otherwise skies will be mostly clear through the period except for some high clouds on Wednesday. Gusty onshore winds will affect the mountains and deserts during the afternoon and evening hours through the coming week. Temperatures will be a few degrees below normal along the coast and near to slightly above normal inland. && .SHORT TERM (SAT-TUE)...20/901 PM. The latest fog product imagery shows stratus well-entrenched and stretching into the coastal and valley areas this evening. Stratus should continue to fill in overnight and into Sunday morning. The latest AMDAR soundings from KLAX indicate a marine layer depth near 1650 feet deep, which agrees well with 00Z KVBG RAOB soundings. The current forecast of a marine layer depth near 1800 feet is reasonable, but the latest NAM-WRF solutions suggest the marine layer deepening to closer to 2300 feet late this evening or later tonight, then thinning toward daybreak Sunday. The marine layer should thin and onshore flow should weaken some over the into early next week as high pressure aloft builds east into the California coast through Monday. The beaches and coastal areas will likely to struggle to clear again on Sunday afternoon and clouds will likely hug the coast as the high pressure building in aloft clamps down on the marine layer. A strong marine inversion will likely inhibit the clouds from mixing out. A few tweaks will be made to the forecast to account for an earlier arrival tonight and slow clearing on Sunday. ***From Previous Discussion*** Upper level ridging will slowly build over the area thru early next week with H5 heights increasing from about 588 dm today to around 592 dm by Mon afternoon, with little change expected through Tue. The upper level ridging will help to gradually lower the marine inversion through early next week. The marine layer depth should be around 1200 to 1800 ft or so tonight into Sun morning, and about 800 to 1200 ft Sun night into Mon morning, and again Mon night into Tue morning. The marine layer pattern will continue west of the mtns with night and morning low clouds and fog for the coast and vlys, altho the inland intrusion of the low clouds will decrease thru early next week. In fact, it looks like the low clouds should be confined mainly to the coastal plain Sun night into Mon morning, with just some low clouds and fog extending into the adjacent vlys. A further decrease in inland extent of the low clouds is expected Mon night into Tue morning as well. The low clouds should clear to or off the coast each day thru Tue, but continued strong onshore gradients may result in only partial afternoon clearing at some of the beaches. Otherwise, mostly clear skies can be expected across the region through the period. The NAM forecasts the gradients from LAX-DAG to continue to be quite strong Sun afternoon at around +9.2 mb, then turn slightly lower to +8.8 mb Mon afternoon and +8.4 mb Tue afternoon. Breezy to gusty S to W afternoon and early evening winds will continue across many areas each day. The strongest winds should be in the Antelope Vly on Sun, but gusts should remain at sub-advisory levels. Temps on Sun are forecast to be several degrees below seasonal norms for the coast and adjacent vlys, and several degrees above normal for interior areas. On Mon, the coast and vlys should warm to near normal to a few degrees below normal, while the interior vlys, mtns and deserts heat up further to about 4-10 deg above normal. Coastal areas should remain several degrees below normal on Tue, while the vlys, mtns and deserts warm up further to about 4-12 deg above normal. Highs on Tue in the warmest interior vlys and Antelope Vly should reach the low 100s. .LONG TERM (WED-SAT)...20/140 PM. Upper level ridging will persist into Wed. The EC forecasts upper level ridging to continue Thu thru Sat, while the GFS brings a weak upper level trof into the region Thu into Fri with weak upper ridging moving back in Sat. The EC is the warmer solution overall but went with a blend of the EC and GFS for the extended period. At the surface, good onshore gradients will continue with the marine layer pattern persisting. Night and morning low clouds and fog are expected mainly for the coastal plain with only minor intrusion into the adjacent vlys. Otherwise, mostly clear skies will continue thru the extended period except some hi clouds should bring a period of partly cloudy skies to the area Tue night and Wed. Temps will continue to be about 4-12 deg above normal on Wed for the vlys, mtns and deserts, with slightly cooler than normal conditions for the coast. The coast and vlys should turn slightly cooler Thu thru Sat to near normal to slightly above normal. However, the far interior vlys, mtns and deserts should be slightly above normal overall thru the period. && .AVIATION...21/0035Z. At 23Z, the marine layer depth was around 1800 feet deep at KLAX. The top of the inversion was around 3800 feet with a temperature of 24 degrees Celsius. North of Point Conception, moderate confidence in the current forecast. LIFR to IFR conditions will spread into coastal and coastal valley terminals through 06Z, then likely drop to the LIFR category between 06Z and 16Z. There is a chance of VLIFR conditions between 10Z and 14Z. Conditions should improve one category between 15Z and 17Z. VFR conditions at coastal terminals should develop about 30 minutes to an hour later than today. South of Point Conception, moderate confidence in the current forecast. IFR to MVFR conditions will spread into coastal and coastal valley terminals through 08Z. There is a chance of terminals becoming predominately IFR between 10Z and 16Z. Conditions should improve one category between 16Z and 18Z. VFR conditions should develop as soon as 18Z, or as late as 22Z. KOXR and KSBA may not clear at all on Sunday. KLAX...MVFR conditions will likely continue through at least 19Z. There is a 30 percent chance of IFR conditions between 10Z and 16Z. Conditions should improve one category between 16Z and 18Z. VFR conditions should develop as soon as 19Z, or as late as 21Z. KBUR...MVFR conditions will spread into KBUR between 04Z and 07Z. There is a 60 percent chance of IFR between 09Z and 16Z. Conditions should improve one category between 15Z and 17Z. VFR conditions should develop around 18Z. && .MARINE...20/728 PM. Overall, moderate to high confidence in forecast. There is a 60% chance of Small Craft Advisory (SCA) level conditions over the outer waters north of Point Sal. Gusty NW winds will then expand in areal coverage on Sunday, and there is a 60% chance that winds will exceed SCA level across the outer waters from Point Sal to San Nicolas Island by Sunday afternoon. Then on Monday, the focus of the gusty winds will be focused from Point Conception to San Nicolas Island. For both Sunday and Monday, there is a 30% chance that SCA level winds will affect the western portion of the Santa Barbara Channel. For Tuesday through Thursday, high confidence that winds and seas will be below SCA criteria. Night through morning patchy fog will continue across the waters through next week. North of Point Conception fog may be locally dense with visibility under one nautical mile. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...Small Craft Advisory in effect until 3 AM PDT Monday for zone 670. (See LAXMWWLOX). Small Craft Advisory in effect from 3 PM Sunday to 3 AM PDT Monday for zones 673-676. (See LAXMWWLOX). && .HAZARD POTENTIAL OUTLOOK (TUE-SAT). No significant hazards expected. && $$ PUBLIC...Hall/Sirard AVIATION...Hall MARINE...Smith SYNOPSIS...Smith