SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NWS LOS ANGELES/OXNARD CA
AFDLOX 900 PM PDT FRI MAY 11 2001
RATHER INTERESTING WEATHER SHAPING UP THIS EVENING. EXTENSIVE LOW
CLOUDS ALONG COASTAL AREAS. UPPER LOW CENTERED NEAR 30N/125W THIS
EVENING SENDING HI CLOUDS STREAMING INTO SOCAL. THERE WAS SOME
THUNDER ACTIVITY EARLIER TODAY OVER SAN COUNTY MOUNTAINS. THIS
CONVECTION INTRODUCED SOME MID LEVEL CLOUDS MAINLY TO L.A. COUNTY
WITH VIRGA REPORTED AT LGB AND SOME SHOWERS NOTED ON KSOX RADAR.
LOW LEVELS TOO DRY FOR RAIN TO REACH THE GROUND...EXCEPT FOR
PERHAPS A FEW SPRINKLES IN THE MOUNTAINS. THESE MID LEVEL SHOWERS
SHOULD DISSIPATE OVERNITE. MORE EXTENSIVE MID AND HI LEVEL MOISTURE
WILL PUSH INTO THE DISTRICT OVERNIGHT. DIFFICULT TO SAY HOW THESE
CLOUDS MAY IMPACT THE MARINE LAYER. THIS IS A SITUATION PERHAPS
WHERE ONLY TIME WILL TELL. ONSHORE GRADIENTS SHOULD HELP TO BRING
THE MARINE LAYER CLOUDS INLAND...AND WITH MARINE LAYER DEPTH NEAR
1500 FEET ACCORDING TO VBG AND ACARS SOUNDINGS...LOW CLOUDS SHOULD
MOVE INTO THE VALLEYS LATER TONIGHT AS WELL. FELT SOME DRIZZLE
LOCALLY HERE AT THE OFFICE...SO WILL ADD PATCHY DRIZZLE TO
APPROPRIATE COAST AND VALLEY AREAS FOR TONIGHT.
UPPER LOW IS FORECAST TO WEAKEN INTO A TROUGH THROUGH SAT AS IT
DRIFTS OFF TO THE NE TOWARD SOCAL. AT THE SAME TIME...THE MESO-ETA
HAS AN ELONGATED VORT MAX MOVING OVER THE DISTRICT BETWEEN 18Z SAT
AND 00Z SUN. THIS COMBINED WITH STRONG MAY SUNSHINE...AND MID AND
UPPER LEVEL MOISTURE...SHOULD BE ENOUGH TO TRIGGER SOME MOUNTAIN
CONVECTION. ALONG COASTAL AREAS...THE MARINE LAYER CLOUDS SHOULD
DISSIPATE BACK TO THE COAST. IT IS INTERESTING TO NOTE THAT THE
MESO-ETA FOR AT LEAST THE PAST TWO RUNS HAS DRIED OUT THE BOUNDARY
LAYER BETWEEN SAT AND SUN...SUGGESTING MARINE LAYER INTRUSION WILL
BE AT A MINIMUM SAT NITE INTO SUN. WILL WAIT A FEW MORE RUNS ON
THIS IDEA. APPARENTLY MESO-ETA THINKS ENOUGH SUBSIDENCE BEHIND WEAK
SHORTWAVE WILL BE ENOUGH TO DRY OUT BOUNDARY LAYER. AT THIS
TIME...WILL NOT CHANGE 3RD OR 4TH PERIOD THINKING WITH REGARD TO
MARINE LAYER CLOUDS. AT ANY RATE...WEAK UPPER TROUGH IS FORECAST TO
LINGER JUST OFF THE SOCAL COAST THROUGH SUN. WITH MORE OF A SW FLOW
ALOFT AND LESS MOISTURE ALOFT...MOUNTAIN CONVECTION SHOULD BE
LIMITED SUN.
WILL UPDATE ZONES BY 930 PM TO ADD PATCHY DRIZZLE TO SEVERAL COAST
AND VALLEY ZONES FOR TONIGHT AND SAT MORNING. ALSO...WILL CHANGE ANY
MOSTLY CLEAR WORDING TO VARIABLE CLOUDS FOR TONIGHT. OTHERWISE...
REMAINDER OF ZONES INCLUDING TEMPS LOOK REASONABLE AT THIS TIME.
IN THE EXTENDED...WEAK UPPER TROF LINGERS THROUGH MON
MORNING...THEN THE EASTERN END OF AN EASTERN PAC UPPER HI WILL
BUILD INTO SOCAL LATER MON THRU WED. DRY AND WARM WEATHER SHOULD
PREVAIL...EXCEPT AT THE COAST SOMEWHAT COOL WITH A MARINE LAYER
INFLUENCE CONTINUING.
LAX 0000. SIRARD
.LAX...NONE.