Forecast Discussions mentioning any of "ACARS" "MDCRS" "AIRCRAFT" "TAMDAR" "AMDAR" "WVSS" received at GSD on 06/19/19

Area Forecast Discussion
National Weather Service Los Angeles/Oxnard CA
840 PM PDT Tue Jun 18 2019 .SYNOPSIS...18/814 PM. For the rest of the week, onshore winds will keep thick clouds over coastal areas. These clouds will push into the valleys overnight, with patchy fog and possible drizzle by morning. Temperatures will trend cooler into Friday, and warming more by the weekend as clouds dimish. && .SHORT TERM (TUE-FRI)...18/839 PM. A weak offshore wind influence along with rising heights allowed for better clearing today across the valleys, with triple digit heat in the Antelope Valley. However, June gloom was in full swing once again, with low clouds lingering across many coastal areas through the day. ACARS soundings and Vandenberg sounding showing marine layer depth around 2500 feet this evening, down slightly from this time yesterday. Satellite imagery showing low clouds surging inland quickly once again this evening, already reaching some of the coastal valleys. There were a few cloud build-ups over the local mountains and deserts this afternoon, but all thunderstorm activity remained to the north in Kern county. While there continues to be instability across the mountains and deserts on Wednesday afternoon, only expecting some cloud build-ups once again due to limited moisture and upper level ridging. Despite the upper level ridge of high pressure building in from the west, onshore flow expected to be slightly stronger on Wednesday, with low clouds likely surging inland into the Santa Clarita Valley and little to no clearing across coastal areas in the afternoon hours. Little change in temperatures on Wednesday, then a cooling trend on Thursday as the next upper level trough moves into northern and central California. This system will likely deepen up the marine layer to around 3500 feet by Thursday morning, with low clouds and fog surging into the lower coastal slopes. This deepening of the marine layer could bring some patchy drizzle to the region on Thursday morning, along with less clearing for coastal/valley areas in the afternoon hours. As a result, look for additional cooling in all areas on Thursday. Also of note, the stronger onshore flow combined with some upper level onshore wind support will generate stronger onshore winds in the Antelope Valley on Thursday, with advisory level gusts up to 45 mph possible in the afternoon and evening hours (with isolated gusts to 55 mph possible in the foothills). In fact, the LAX-Daggett gradient could peak over +10 mb onshore on Thursday. The strong onshore wind pattern will bring elevated fire weather conditions to the Antelope Valley on Thursday, continuing into Friday. The very strong onshore pressure gradients continue into Friday. The high pressure will recede and a little trof moves southwest out of Nevada and over LA county. This trof will interact with the marine layer and the onshore flow and probably produce some drizzle over the coasts and valleys of LA county. The trof will bring lower heights which will lead to more cooling. Friday will be the coolest day of the next 7 with max temps 10 to 15 degrees below normal. .LONG TERM (SAT-TUE)...18/205 PM. Very weak ridging is expected over the weekend along with offshore trends - both of which will help the marine layer clouds clear earlier and allow afternoon high temperatures to rise. By Sunday, temperatures will be near normal across the interior but will still be 5 to 10 degrees below normal across the coasts and valleys. Another trof will arrive Monday, this time from the northwest, bringing back the strong onshore flow, less clearing and cooler coastal temperatures. && .AVIATION...18/2355Z. At 1731Z, the marine layer depth was around 2400 feet deep at KLAX. The top of the inversion was near 4300 feet with a temperature of 24 degrees Celsius. Moderate confidence in the current forecast. Higher confidence in categories, less confidence in timing. Expecting low clouds to be extensive overnight into Wednesday morning across coastal/valley areas. With strong onshore flow expected on Wednesday, look for little to no clearing across portions of the coast including KLAX, KSMO, KOXR, KCMA, and KSBA. KLAX...MVFR cigs are generally expected at KLAX through the period. There is a 30 percent chance of brief clearing late Wednesday afternoon/early evening. KBUR...MVFR cigs expected to develop overnight into Wednesday morning, otherwise VFR conditions. There is a 20 percent chance of IFR cigs during this time. && .MARINE...18/812 PM. Winds and seas will likely remain below Small Craft Advisory (SCA) levels through at least Thursday. There is a 30 percent chance for advisory level seas and winds across the outer water for Friday and through the weekend. && .LOX WATCHES/WARNINGS/ADVISORIES... CA...NONE. PZ...NONE. && .HAZARD POTENTIAL OUTLOOK (FRI-TUE). No significant hazards expected. && $$ PUBLIC...Gomberg/jld AVIATION...Gomberg MARINE...Sweet SYNOPSIS...Phillips