976 
FXUS66 KLOX 132125
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
120 PM PST WED NOV 13 2013

.SYNOPSIS...

ANOTHER WARM DAY TODAY BUT A COOLING TREND WILL BEGIN TOMORROW AND 
AFTERNOON TEMPERATURES WILL BE DOWN TO BELOW NORMAL BY SATURDAY. THE 
MARINE LAYER WILL RETURN FRIDAY NIGHT AND THERE IS A SLIGHT CHANCE 
OF SHOWERS FOR LOS ANGELES COUNTY SATURDAY AND EARLY SUNDAY.

&&

.SHORT TERM (TODAY-SAT)...A HOT DAY TODAY WITH SOME RECORDS BROKEN 
(THOUGH DOWNTOWN LA FELL SHORT OF ITS RECORD OF 96 IN 1933). 
OFFSHORE GRADIENTS EXPECTED TO WEAKEN THURSDAY AS A TROF APPROACHES 
NORTHERN CALIFORNIA. THE AIR MASS WILL BE COOLING AS WELL SO THIS 
MAKES FOR A TRICKY HIGH TEMPERATURE FORECAST FOR COAST/VALLEYS. MOST 
AREAS WILL GET OFF TO A QUICK START, PERHAPS BRIEFLY WARMER THAN 
TODAY, BUT THEN WARMING WILL CEASE MUCH EARLIER AS A SEA BREEZE 
DEVELOPS AND PUSHES INLAND. SO WHILE 9 AM TEMP TRENDS MAY BE UP IN 
SOME AREAS, 1 PM TEMPERATURE TRENDS WILL BE NOTICABLY COOLER, 
ESPECIALLY CLOSER TO THE COAST, POSSIBLY AS MUCH AS 15 DEGREES IN 
SOME SPOTS.

THE PREVIOUSLY MENTIONED TROF WILL BE THE FIRST OF TWO TO IMPACT OUR 
AREA THROUGH THE WEEKEND. THIS ONE WILL MOVE THROUGH FRIDAY AND THE 
MAIN IMPACT WILL BE FURTHER COOLING, AN INCREASE IN MARINE LYR 
CLOUDS FOR MAINLY LA COUNTY, AND A STRONG INCREASE IN NORTHWEST FLOW 
ACROSS MUCH OF THE AREA, THOUGH MOST NOTICABLY FOR THE OFFSHORE 
WATERS, CENTRAL COAST, SRN SBA COUNTY, AND THE MTNS AND ANTELOPE 
VALLEY. 

THE SECOND TROF WILL MOVE THROUGH SATURDAY AND THERE ARE SOME MODEL 
DIFFERENCES WITH THIS ONE. THE GFS FAVORS A MORE INLAND TRAJECTORY 
WITH LESS COLD AIR DROPPING INTO CALIFORNIA WHILE THE NAM AND ECMWF 
ARE FURTHER WEST AND COLDER. ALL SOLUTIONS SUPPORT A DEEPENING 
MARINE LYR FOR LA COUNTY, FURTHER INCREASE IN NORTHWEST FLOW, AND A 
STRONG EDDY CIRCULATION POSSIBLY GENERATING SOME LIGHT PRECIP FOR 
SOUTHEASTERN LA COUNTY (ESPECIALLY THE SAN GABRIEL FOOTHILLS AND 
MTNS). HAVE KEPT IN SOME LOW POPS FOR THOSE AREAS. MAY NEED TO BOOST 
THEM IF COLDER/FARTHER WEST SOLUTIONS PAN OUT, THOUGH AT THIS POINT 
NOT EVEN COMPLETELY SOLD ON CLOUD COVERAGE DUE TO THE STRONG 
NORTHWEST FLOW BEHIND DEVELOPING BEHIND THE FRIDAY TROF. THERE WILL 
LIKELY BE A SIGNIFICANT DECREASE IN CLOUD COVERAGE FROM ORANGE 
COUNTY/IE UP THROUGH SRN SBA COUNTY DUE TO THE LOW LVL SUBSIDENCE 
FROM THE NW WINDS BUT DIFFICULT TO PIN POINT WHERE EXACTLY THE 
CLOUDS WILL STOP. THE NAM ALSO HAS MORE MOISTURE MOVING INTO NRN SLO 
COUNTY SAT AFTERNOON AND WILL NEED TO FOLLOW THE MODELS CLOSELY TO 
SEE IF SOME SMALL POPS WILL BE NEEDED UP THERE AS THE FRONT MOVES 
THROUGH DURING THE DAY. ADVISORY LEVEL WEST WINDS POSSIBLE FOR THE 
ANTELOPE VALLEY AS ONSHORE GRADIENTS REALLY KICK IN. AND MAY ALSO 
NEED ADVISORIES FOR SRN SBA COUNTY FOR NORTHERLY WINDS THROUGH THE 
PASSES. DAYTIME HIGHS (CLOUDS OR NO CLOUDS) SHOULD TOP OUT IN THE 
60S FOR MOST COAST/VALLEY LOCATIONS.

.LONG TERM (SUN-WED)...SOME LINGERING CLOUDS/LIGHT PRECIP POSSIBLE 
FOR EASTERN LA COUNTY SUNDAY MORNING, OTHERWISE SKIES CLEARING OUT 
BEHIND THE TROF WITH DRIER NORTHWEST FLOW. MOST AREAS SHOULD SEE AT 
LEAST A FEW DEGREES OF WARMUP SUNDAY WITH MUCH LESS WIND. THE 
WARMING TREND TO CONTINUE THROUGH THE TUESDAY UNDER CLEAR SKIES. A 
LITTLE TROF PASSES TO THE NORTH TUE AND EARLY WEDNESDAY WILL HAVE 
LITTLE TO NO IMPACT LOCALLY OTHER THAN POSSIBLY STALLING THE WARMING 
TREND BRIEFLY. THE GFS SHOWS A STRENGTHENING RIDGE FOR THE END OF 
NEXT WEEK WITH SOME OFFSHORE FLOW, SUGGESTING ANOTHER SIGNIFICANT 
WARMUP NEXT THU/FRI, THOUGH THE ECMWF/GEM SOLUTIONS ARE WEAKER. NOT 
SEEING ANY MODELS SHOWING ANY RAIN OUTSIDE OF THE DEEP MARINE LYR 
DRIZZLE/LIGHT SHOWERS FOR ERN LA COUNTY THIS WEEKEND SO OUR DRY FALL 
AND VERY DRY 2013 WILL LIKELY CONTINUE AT LEAST FOR THE NEXT 10 DAYS 
OR SO.

&&

.AVIATION...13/1115Z...

OVERALL...HIGH CONFIDENCE IN 12Z TAF PACKAGE. WEAK OFFSHORE FLOW WILL
KEEP ALL SITES VFR THROUGH THE PERIOD. 

KLAX...HIGH CONFIDENCE IN 12Z TAF.

KBUR...HIGH CONFIDENCE IN 12Z TAF. 

&&

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

&&

$$

PUBLIC...MW
AVIATION...HALL
SYNOPSIS...KJ

WWW.WEATHER.GOV/LOSANGELES