Weather Service Report


505 
FXUS66 KLOX 190012 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
510 PM PDT FRI APR 18 2014

...UPDATE FOR NEW AVIATION DISCUSSION...

.SYNOPSIS...

A SLIGHT CHANCE OF THUNDERSTORMS IN THE LOS ANGELES AND VENTURA 
COUNTY MOUNTAINS AND DESERTS THIS AFTERNOON AND EVENING.  CLEARING 
AND WARMING OVER THE WEEKEND...WITH TEMPERATURES ABOVE NORMAL SUNDAY 
AND MONDAY. THEN COOLING BACK DOWN TO NORMAL AS A TROUGH MOVES 
THROUGH OUR AREA ON TUESDAY.   
 
&&

.SHORT TERM (TODAY-MON)...UPPER LOW MOVING ONSHORE NEAR THE US/MX 
BORDER THIS AFTERNOON. THE THICK HIGH CLOUD SHIELD HAS MOVED EAST 
LEAVING BEHIND A DEEP LOW LVL MOIST LAYER UP TO AROUND 4000' AND 
SOME WEAK INSTABILITY OVER THE MTNS. SO FAR NOT MUCH GOING ON EXCEPT 
FOR A FEW LIGHT CU BUT SINCE THE HIGHER CLOUDS HAVE MOVED EAST THERE 
WILL BE AMPLE SUNSHINE TO ALLOW SURFACE HEATING TO GENERATE SOME 
MORE CU THIS AFTERNOON AND POSSIBLY EVEN A BRIEF SHOWER. WINDS ALOFT 
HAVE SHIFTED TO THE NORTH SO IF A SHOWER WERE TO FORM OVER THE MTNS 
IT COULD DRIFT OVER THE VALLEYS. 

A SOMEWHAT TRICKY LOW CLOUD FORECAST FOR TONIGHT IN THE WAKE OF THE 
TROF PASSAGE, ESPECIALLY SOUTHERN AREAS. MODELS SHOW PLENTY OF LOW 
LVL MOISTURE BUT A FAIRLY WEAK INVERSION SO THE LOW CLOUDS MAY NOT 
BE ALL THAT SOLID SOUTH OF PT CONCEPTION. WITH THE RIDGE BUILDING TO 
THE NORTH TONIGHT INTO SATURDAY THE INVERSION DOES STRENGTHEN UP 
THERE OVERNIGHT WITH THE WARMER AIR ALOFT MOVING IN SO CONFIDENCE A 
LITTLE HIGHER IN LOW CLOUD COVERAGE NORTH OF PT CONCEPTION, 
INCLUDING THE SOUTHERN SALINAS VALLEY. HIGHS SATURDAY EXPECTED TO 
WARM UP ABOUT 5 DEGREES INLAND AND A COUPLE DEGREES AT THE COAST 
WITH PLENTY OF SUNSHINE BY AFTERNOON.

WARMING TREND TO CONTINUE SUNDAY WITH LIGHT NORTHERLY FLOW AT LOW 
LVLS. LIKELY ANOTHER 5 DEGREES OF WARMING ON AVERAGE WITH VALLEYS IN 
THE LOW TO MID 80S. MARINE LYR WILL BE SHRINKING IN DEPTH AND LIKELY 
CONFINED TO THE CENTRAL COAST AND SRN LA COUNTY.

GRADIENTS START TRENDING STRONGLY ONSHORE SO COASTAL AREAS LIKELY 
WILL BE A LITTLE COOLER, BUT VALLEYS AND OTHER INLAND AREAS EITHER 
LITTLE CHANGE OR PERHAPS A DEGREE OR TWO WARMER. 

.LONG TERM (TUE-FRI)...A TROF MOVES IN TUESDAY WITH A WEAK COLD 
FRONT DYING AS IT APPROACHES THE CENTRAL COAST. THE GFS AND ECMWF 
SPIT OUT A COUPLE HUNDREDTHS NORTH OF PT CONCEPTION TUESDAY MORNING 
BUT DRY ELSEWHERE. LOOKS LIKE AT BEST A DEEP MARINE LYR/DRIZZLE 
EVENT FOR OUR AREA SO WILL KEEP POPS BELOW 15 FOR NOW. MAIN THING 
WITH THIS SYSTEM WILL BE GUSTY POST-FRONTAL WINDS TUESDAY AFTERNOON 
AND EVENING AS STRONG ONSHORE FLOW DEVELOPS. HIGHS WILL DROP A GOOD 
10-15 DEGREES MOST AREAS TUESDAY. COOL AND BREEZY AND AGAIN 
WEDNESDAY BUT WITH LESS CLOUDS. THEN TURNING WARMER TOWARDS THE END 
OF THE WEEK AS WEAK HIGH PRESSURE ALOFT DEVELOPS. 

&&

.AVIATION...19/0005Z...MODERATE CONFIDENCE OVERALL IN THE 00Z TAFS. 
THERE IS UNCERTAINTY IN THE EXTENT OF LOW CLOUDS AND MVFR CONDITIONS 
AT THE COASTAL AND VLY AIRFIELDS...AND UNCERTAINTY WITH THE TIMING 
OF THE LOW CLOUD DEVELOPMENT FOR KPRB AND THE AIRFIELDS S OF POINT 
CONCEPTION WHICH COULD BE OFF AN HOUR TOO LATE TO 1 TO 3 HOURS TOO 
EARLY. THERE IS ALSO TIMING ISSUES FOR THE LOW CLOUDS SCATTERING OUT 
TO VFR CONDITIONS SAT MORNING WHICH COULD BE OFF PLUS/MINUS AN HOUR 
OR TWO. FOR KWJF AND KPMD...HI CONFIDENCE IN THE 00Z TAFS WITH VFR 
CONDITIONS THRU SAT.

.KLAX...MODERATE CONFIDENCE OVERALL IN THE 00Z TAF WITH 
UNCERTAINTIES IN THE TIMING OF THE ONSET OF LOW CLOUDS AND MVFR 
CONDITIONS THIS EVENING WHICH MAY BE OFF FROM AN HOUR TOO LATE TO A 
COUPLE OF HOURS TOO EARLY. THERE ARE ALSO UNCERTAINTIES WITH THE 
TIMING OF THE LOW CLOUDS SCATTERING OUT TO VFR CONDITIONS ON SAT 
WHICH MAY BE OFF PLUS/MINUS AN HOUR OR TWO. VFR CONDITIONS SHOULD 
PREVAIL FOR MOST OF SAT AFTERNOON THRU THE EVENING.

.KBUR...MODERATE CONFIDENCE OVERALL IN THE 00Z TAF WITH 
UNCERTAINTIES IN THE TIMING OF THE ONSET OF LOW CLOUDS AND MVFR 
CONDITIONS THIS EVENING WHICH MAY BE OFF FROM AN HOUR TOO LATE TO A 
COUPLE OF HOURS TOO EARLY. THERE ARE ALSO UNCERTAINTIES WITH THE 
TIMING OF THE LOW CLOUDS SCATTERING OUT TO VFR CONDITIONS ON SAT 
MORNING WHICH MAY BE OFF PLUS/MINUS AN HOUR OR TWO. VFR CONDITIONS 
SHOULD PREVAIL FOR MOST OF SAT AFTERNOON.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...MW
AVIATION...SIRARD
SYNOPSIS...JLD

WWW.WEATHER.GOV/LOSANGELES



Return to Home page


Western Regional Climate Center, wrcc@dri.edu