FXUS66 KLOX 030553
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
955 PM PST WED DEC 2 2009
...NEW AVIATION DISCUSSION...
.SYNOPSIS...
EXPECT SOME MARINE LAYER CLOUDS AND PATCHY FOG TONIGHT AND THURSDAY
MORNING OVER THE COAST AND VALLEYS. COOL TEMPERATURES WILL PERSIST
THURSDAY. WEAK OFFSHORE FLOW WILL DEVELOP FRIDAY...WARMING
TEMPERATURES AND CLEARING OUT THE MARINE LAYER. A LOW PRESSURE
SYSTEM WILL MOVE INTO THE AREA MONDAY...WITH RAIN BECOMING LIKELY.
&&
.SHORT TERM (TONIGHT-SAT)...MARINE INVERSION NEAR 4000 FT DEEP AT
LAX THIS EVENING. SOME OFFSHORE GRADIENT TRENDS AND OFFSHORE FLOW
AT A FEW THOUSAND FEET OFF THE GROUND WAS MINIMIZING LOW CLOUD
DEVELOPMENT AND COVERAGE OVER AREAS S OF POINT CONCEPTION THIS
EVENING. SOME STRATOCU WAS LINGERING FROM LATE THIS AFTERNOON BUT
HAVE LARGELY DISSIPATED THIS EVENING. DIFFICULT TO DETERMINE IF LOW
CLOUDS WILL REFORM OVERNIGHT...ALTHO THE WRF BOUNDARY LAYER RH
FORECAST WOULD INDICATE PERHAPS PATCHY LOW CLOUDS COULD DEVELOP. N
OF POINT CONCEPTION IT IS A DIFFERENT STORY AS LOW CLOUDS HAVE
BECOME WIDESPREAD OVER THE COAST AND SANTA YNEZ VALLEY AND SHOULD
PERSIST OVERNIGHT. LOW CLOUDS SHOULD ALSO AFFECT THE SALINAS RIVER
VALLEY LATE TONIGHT AS WELL. OTHERWISE IT APPEARS MOST OF THE
DISTRICT WILL HAVE MOSTLY CLEAR SKIES TONIGHT.
AN UPPER LEVEL RIDGE IS EXPECTED TO BUILD OFF THE CENTRAL CA COAST
ON THU...THEN WEAKEN WHILE MOVING INLAND OVER CA ON FRI. BROAD UPPER
LEVEL TROFFINESS WILL THEN MOVE INTO THE STATE FOR FRI NIGHT AND
SAT. LITTLE IN THE WAY OF MOISTURE WILL BE ASSOCIATED WITH THE UPPER
TROF ON SAT...WITH DRY WEATHER EXPECTED TO LINGER OVER THE FORECAST
AREA THU THRU SAT. IT LOOKS LIKE THERE WILL BE WEAK OFFSHORE FLOW
OVER THE AREA LATER TONIGHT INTO THU MORNING...WITH STRONGER
OFFSHORE FLOW EXPECTED THU NIGHT INTO FRI...ESPECIALLY OVER PORTIONS
OF VTU/L.A. COUNTIES. GUSTY NE CANYON WINDS WILL DEVELOP THU NIGHT
BUT AT THIS TIME IS APPEARS WINDS WILL REMAIN BELOW ADVISORY LEVELS
FOR THE MOST PART. THE LOW LEVEL FLOW WILL BE RATHER WEAK FRI NIGHT
THEN TURN ONSHORE AND INCREASE ON SAT. MARINE LAYER CLOUDS WILL BE
PUSHED OFF THE COAST THU NIGHT AND FRI...BUT SOME MAY RETURN TO THE
CENTRAL COAST FRI NIGHT INTO SAT MORNING. OTHERWISE MOSTLY CLEAR
SKIES CAN BE EXPECTED OVER THE REGION THRU FRI...THEN SOME HI CLOUDS
WILL MOVE INTO THE REGION FRI NIGHT AND SAT FOR PARTLY CLOUDY
CONDITIONS AT TIMES. TEMPS OVER THE REGION ARE EXPECTED TO BE
SLIGHTLY MILDER ON THU BUT STILL A COUPLE OF DEGREES BELOW
NORMAL...THEN WARM TO AROUND SEASONAL NORMS FOR FRI BEFORE FALLING
BACK TO SLIGHTLY BELOW NORMAL SAT.
...FROM PREVIOUS DISCUSSION...
.LONG TERM (SUN-WED)...PRETTY ACTIVE WEATHER PATTERN NEXT WEEK. ON
SUNDAY, THE MODELS ARE NOW IN DECENT AGREEMENT SHOWING THE COLD
UPPER LOW ON THE EAST SIDE OF THE OMEGA BLOCK ACTUALLY RETROGRADING
OFFSHORE. THE GFS HAD EARLIER INDICATED THIS LOW DROPPING SOUTH INTO
THE GREAT BASIN SO MODEL AGREEMENT HAS IMPROVED DRAMATICALLY. BUT
THIS ACTUALLY SLOWS THE ARRIVAL OF THE MOISTURE INTO OUR AREA, SO IT
NOW APPEARS THAT THE MAJORITY OF SUNDAY WILL REMAIN DRY. HOWEVER,
HEIGHTS WILL BE FALLING PRETTY RAPIDLY, ALLOWING THE MARINE
INVERSION TO DEEPEN SIGNIFICANTLY, PERHAPS SIMILAR TO TODAY'S LEVEL.
THUS, A COOL AND CLOUDY DAY EXPECTED SUNDAY WITH JUST PARTIAL
AFTERNOON CLEARING AT BEST.
ALL MODELS NOW ON BOARD WITH THE FIRST SHOT OF RAIN ARRIVING INTO
THE AREA EITHER SUNDAY NIGHT OR MONDAY MORNING. THE CANADIAN AND THE
ECMWF SHOW THE SURFACE LOW ABOUT 300 MILES NORTHWEST OF SFO 12Z MON
WITH A GOOD WARM FRONTAL PATTERN SETTING UP OVER SO CAL. THIS
PATTERN TYPICALLY PRODUCES A STEADY, BUT MOSTLY LIGHT RAIN FOR OUR
AREA, THOUGH IT REMAINS TO BE SEE HOW MUCH SOUTHERLY FLOW SETS UP TO
POSSIBLY ENHANCE THE RAIN ALONG THE MOUNTAIN SLOPES.
MODELS START TO DIVERGE TUE, THOUGH IT'S MAINLY THE GFS THAT IS THE
OUTLIER HERE SHOWING THAT UPPER LOW ON THE EAST SIDE OF THE OMEGA
BLOCK DROPPING SOUTH INTO THE GREAT BASIN AND PUSHING THE MOISTURE
SOUTH OF THE AREA AND USHERING IN A LOT OF COLD AIR. FOR NOW HAVE
DECIDED TO IGNORE THE GFS AND WENT WITH THE EC/CANADIAN SOLUTION.
THIS SOLUTION MAINTAINS A RELATIVELY WARM, MOIST FLOW OF AIR ACROSS
THE AREA TUE WITH PERIODS OF RAIN CONTINUING, AGAIN MOSTLY ON THE
LIGHTER SIDE WITH THE CAVEAT THAT IT REMAINS TO BE SEEN HOW MUCH
SOUTHERLY FLOW SETS UP.
NOT TOO MUCH CHANGE ON WED, THOUGH IF THERE IS A BREAK IN THE WET
WEATHER NEXT WEEK WED WILL LIKELY BE THE DAY WE SEE THE LEAST AMOUNT
OF PRECIP. ALTHOUGH THURSDAY IS BEYOND THE CURRENT FORECAST CYCLE,
THAT COULD BE THE WETTEST DAY NEXT WEEK AS THE ECMWF SHOWS THE BEST
MOISTURE/SOUTHERLY FLOW COUPLING THAT COULD GENERATE HEAVIER RAIN.
&&
.AVIATION...
03/0555Z...
MARINE LAYER ABOUT 015 NORTH OF POINT CONCEPTION AND MARINE LAYER
CLOUDS WILL COVER THE COASTS AND VLYS THROUGH MID TO LATE MORNING.
MARINE LAYER IS 3700 DEEP SOUTH OF POINT CONCEPTION BUT HAS BEEN
DISRUPTED TO THE POINT WHERE CLOUDS HAVE NOT FORMED. WITH FLOW
TRENDING OFFSHORE THERE IS A SLIGHTLY BETTER CHC THAT CLOUDS WILL
NOT REFORM OVER MUCH OF THE AREA. BUT STILL THERE IS ABOUT A 40
PERCENT CHANCE OF CLOUDS DEVELOPING OVERNIGHT WHERE THEY ARE NOT
FORECAST AND A SIMILAR 40 PERCENT CHANCE OF CLOUDS NOT DEVELOPING
WHERE THEY ARE FORECAST.
KLAX...SO SO CONFIDENCE IN TAF WITH A 40 PERCENT CHANCE OF NO CLOUDS
AT ALL.
KBUR...SO SO CONFIDENCE IN THE CURRENT TAF. THERE IS A 40 PERCENT
CHANCE OF MVFR CIGS BETWEEN THE HOURS OF 10Z AND 17Z.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
PUBLIC...SIRARD/WOFFORD
AVIATION...ASR
SYNOPSIS...MEIER
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