SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
300 AM PDT SAT MAY 4 2002

WIDESPREAD LOW CLOUDS HAVE PUSHED INTO ALL COSTAL SECTIONS N OF PT CONCEPTION. S OF PT CONCEPTION...STRATUS HAS BEGUN TO PUSH INTO COSTAL SECTIONS OF LA. AND VENTURA COUNTIES...AND EXPECT AREAS OF LOW CLOUDS ACROSS THE COSTAL ZONES OF L.A. AND VENTURA COUNTIES BY DAYBREAK. ACARS SOUNDINGS SHOWED THE BASE OF THE INVERSION BETWEEN 1000 AND 1300 FT. FOR THE MOST PART...VALLEYS SHOULD REMAIN CLEAR THIS MORNING. HOWEVER...ONCE AGAIN THERE IS A CHANCE THAT SOME LOW CLOUDS/DENSE FOG COULD SQUEAK INTO THE SAN GABRIEL VALLEY AND THE COSTAL VALLEYS OF VENTURA COUNTY FOR A COUPLE OF HRS AROUND DAYBREAK.

06Z ETA SHOWS A VERY WEAK EDDY CIRCULATION DEVELOPING THIS MORNING...BUT IT IS FORECAST TO QUICKLY DISSIPATE BY AFTERNOON. EXPECT GOOD CLEARING OF THE LOW CLOUDS TODAY...WITH MOST COSTAL ZONES BECOMING SUNNY BY AFTERNOON. A VERY WEAK UPPER LOW OFF THE CENTRAL COAST THIS MORNING WILL DRIFT ACROSS THE FORECAST AREA LATER THIS MORNING. THIS FEATURE MAY CAUSE JUST ENOUGH INSTABILITY TO ALLOW FOR A FEW BUILDUPS ACROSS THE MOUNTAINS TODAY...BUT DO NOT EXPECT ANY SHOWERS. 06Z ETA INDICATES LIFTED INDEX VALUES OF BETWEEN 0 AND 1 ACROSS THE MOUNTAINS THIS AFTERNOON...SIMILAR TO FRI AFTERNOON WHEN SOME BUILDUPS ALSO OCCURRED. TEMPS AT 850 MB AND 950 MB CONT TO WARM...SO EXPECT THE GRADUAL WARMING TREND TO CONT TODAY. MOST AREAS AWAY FROM THE COAST... ESPECIALLY ACROSS THE INLAND VALLEYS...MOUNTAINS AND DESERTS...SHOULD WARM A FEW MORE DEGREES TODAY.

OVERALL UPPER LEVEL PATTERN WILL BE QUITE STATIC THROUGH MON...WITH THE BASE OF A WEAK AND BROAD POSITIVELY-TILTED TROUGH LINGERING ACROSS THE AREA...AND WEAK S/WAVES OCCASIONALLY MOVING THROUGH THE BASE OF THE TROUGH. THICKNESSES AND 850 MB TEMPS WILL...HOWEVER...EDGE UPWARD A BIT MORE ON SUNDAY...SO TEMPS MAY RISE A COUPLE MORE DEGREES IN THE MOUNTAINS
AND DESERTS...WITH LITTLE CHANGE IN TEMPS THERE ON MON.

06Z ETA INDICATES A STRONGER EDDY CIRCULATION TONIGHT AND SUNDAY MORNING... AND ACTUALLY SHOWS SOME COOLING AT 950 MB IN COSTAL AREA S OF PT CONCEPTION. THIS SUGGESTS THAT THE MARINE LAYER MAY BEGIN TO DEEPEN SLIGHTLY LATE TONIGHT AND SUNDAY MORNING...PERHAPS JUST ENOUGH TO BRING SOME CLOUDS INTO THE VALLEYS OF L.A./VENTURA COUNTIES. IN ADDITION... IT WOULD KNOCK TEMPS DOWN A COUPLE OF DEGREES IN THE VALLEYS AS WELL ON SUNDAY. AT THE SAME TIME...SOME WARMING IS FORECAST AT 950 MB ACROSS NORTHERN SBA AND SLO COUNTIES AS FLOW BECOME A BIT MORE NORTHERLY AND LESS ONSHORE...AND INTERIOR SECTIONS OF SLO AND SBA COUNTY MAY WARM A BIT ON SUNDAY.