Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 04/28/19

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
820 PM PDT Sat Apr 27 2019 .SYNOPSIS...27/655 PM. Westerly winds will bring marine clouds, fog, and cool temperatures into the coastal and valley areas tonight and Sunday morning. A storm system approaches on Sunday, bringing more clouds and a chance of mountain showers and thunderstorms. The showers and storms will become more widespread Sunday night, mainly south of San Luis Obispo County. Monday will be mostly dry. && .SHORT TERM (SAT-TUE)...27/818 PM. A strong onshore flow and deep marine layer pattern brought cooler temperatures today and greater low cloud coverage lingering into the afternoon across many coastal plain locations. Current satellite imagery this evening showing low clouds surging quickly inland, with pilot reports and ACARS data showing a marine layer depth around 2300 feet across the LA basin. As an upper level low pressure system approaches the coast over the next 24 hours, the marine layer is expected to lift to between 3000 and 3500 feet by Sunday morning, resulting in low clouds reaching the lower coastal slopes, and areas of drizzle expected for locations south of Point Conception. Would not be surprised to see a few location receive light measurable rainfall, especially across the foothills. Even less clearing expected on Sunday afternoon, with an influx of mid to high level clouds moving into the area associated with the upper low. In evening update, have tweaked temperatures down a few more degrees in many locations on Sunday. A few lightning strikes being picked up near the center of the upper level closed low pressure system this evening, which is currently centered around 550 miles WSW of Point Conception. As the upper low tracks eastward on Sunday, there will be increasing mid level moisture streaming into the region during the afternoon and evening hours. During this time, there is some upper level diffluence and instability across the mountains to warrant the slight chance of thunderstorms over the mountains of Ventura and Santa Barbara counties. Computer models in fairly good agreement that upper low will track through the coastal waters off Southern California later Sunday night through early Monday morning. During this time, there will be colder air aloft (500 mb temperatures as low as -20 degrees Celsius) moving over the region which will help to destabilize areas south of Point Conception including the adjacent coastal waters. 00Z NAM continues to highlight MUCAPE values in the 200-500 J/kg range along with some mid level moisture and lift, resulting in the slight chance of thunderstorms expanding to most areas south of Point Conception including the coastal waters where the low center will be tracking. Rainfall with this system will likely be fairly minimal (mostly drizzle and light rain showers with the deepening marine layer). with Pops generally in the 20-30 percent range for areas south of Point Conception. However there will be the potential for isolated dry lightning strikes as this could be an elevated convective threat above the marine layer clouds. *** From previous discussion *** The deep marine layer will persist Mon night and Tue morning, with low clouds again from the coast up to the coastal slopes along with patchy drizzle in the L.A./VTU County vlys to coastal slopes. The marine layer clouds are expected to clear back to the coast Tue afternoon. Onshore flow will continue Sun thru Tue, best in the afternoon and evening hours. Some gusty S to W winds should continue each afternoon and evening from the foothills to the mtns and deserts, strongest Mon and Tue. Temps will turn cooler each day Sun thru Tue, with highs about 4 to 8 deg below normal in all areas by Mon. The warmest vlys and inland coastal areas should see highs in the 70s on Sun altho likely reach the low 80s in the Antelope Vly. Temps will then be only in the mid 60s to low 70s for these areas on Mon and Tue. .LONG TERM (WED-SAT)...27/206 PM. The EC and GFS are in pretty good agreement Wed and Thu with weak upper level ridging over srn CA. There should be some night and morning low clouds and fog for coastal areas during the period, especially S of Point Conception, otherwise skies will be mostly clear. The forecast confidence goes down quickly for the Fri-Sat timeframe. The EC keeps an upper level low well off the CA coast with weak upper level ridging lingering over srn CA during the period. The GFS, however, moves the upper level low E to near the central CA coast by late Fri then inland thru CA Fri night into Sat, with a cold front and a chance of showers moving into the forecast area. For this forecast cycle have leaned more toward the EC solution with dry weather over the region and some marine layer clouds along the coast at least for Fri. Temps across the region are forecast to be near normal to a few degrees below normal for the most part thru the extended period. Highs in the warmest vlys and inland coastal areas should be generally in the 70s each day, except mid 70s to around 80 on Thu. && .AVIATION...27/2343Z. At 2320z at KLAX... the marine inversion was around 2500 feet. The top of the inversion was around 4200 feet with a temperature of about 19 degrees Celsius. Overall...High confidence in the current TAFs. Late this afternoon, low clouds continue to linger across many coastal areas. Overnight into Sunday morning, marine layer depth will continue to increase to around 3000 feet with low clouds and fog expected to spread into valleys and lower coastal slopes. Also, isolated drizzle expected, especially Los Angeles county. Another slow clearing day expected along the coast on Sunday afternoon. An approaching upper level low pressure system will bring a slight chance of thunderstorms Sunday afternoon across the mountains of Santa Barbara and Ventura counties. KLAX...High confidence in the current TAF. MVFR low clouds will likely continue through much of the forecast period. There is a fifteen percent chance that CIGs will scatter between 21z and 03z. Light southeast winds less than 8 knots are expected Sunday morning. KBUR...High confidence in the current TAF. IFR/MVFR low clouds expected to return to KBUR later this evening into Sunday morning. There is a twenty percent chance that CIGs will remain MVFR throughout Sunday afternoon. && .MARINE...27/733 PM. Winds and seas become elevated Sunday night through Tuesday but will remain below advisory levels throughout the forecast period. There is a slight chance of thunderstorms Sunday night through Monday morning across the southern outer waters and across the inner waters south of Point Conception. Any thunderstorms that develop could produce locally gusty and erratic winds, choppy seas, and dangerous cloud-to-ocean lightning. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (TUE-SAT). No significant hazards expected. && $$ PUBLIC...Gomberg/Sirard AVIATION...Gomberg MARINE...Gomberg/KJ SYNOPSIS...Phillips