243 
FXUS66 KLOX 212151
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
150 PM PST SAT NOV 21 2009

.SYNOPSIS...
TEMPERATURES WILL REMAIN COOL TONIGHT AND SUNDAY IN THE WAKE OF THE 
PASSAGE OF A COLD FRONT. ON MONDAY...HIGH PRESSURE WILL BUILD BACK 
INTO THE AREA AND OFFSHORE FLOW WILL ESTABLISH...QUICKLY WARMING 
TEMPERATURES BACK TO SEASONAL NORMALS. THIS PATTERN WILL PERSIST 
THROUGH THE WEEK...WITH LOCALLY BREEZY CONDITIONS OVER THE MOUNTAINS 
AND ABOVE NORMAL TEMPERATURES FOR THE THANKSGIVING HOLIDAY.

&&

.SHORT TERM (TONIGHT-TUE)...NORTHERLY WINDS CONTINUE TO BRING 
UPSLOPE MOISTURE ON THE NORTH SLOPES OF THE MOUNTAINS THIS AFTERNOON 
AND A FEW CLOUDS REDEVELOPED OVER THE LA BASIN TODAY. WINDS HAVE 
SLOWLY DECREASED ACROSS THE MOUNTAINS THIS AFTERNOON BUT STILL 
REPORTING GUSTS OVER 35 MPH AT TIMES. AS EXPECTED...TEMPERATURES 
HAVE REMAINED ABOUT 5-10 DEGREES BELOW YESTERDAY'S HIGHS IN THE WAKE 
OF THE COLD FRONT. 

MAIN FORECAST CHALLENGE IN THE SHORT TERM CONTINUES TO BE THE 
NORTHERLY WINDS ACROSS THE MOUNTAINS. WILL REISSUE WIND ADVISORIES 
FOR A SUNDOWNER IN THE SANTA YNEZ MOUNTAINS THIS EVENING AND A 
RESURGENCE OF NORTH WINDS OVER THE VENTURA AND LOS ANGELES COUNTY 
MOUNTAINS LATER TONIGHT THROUGH SUNDAY NIGHT. FAIRLY HIGH CONFIDENCE 
IN THIS SCENARIO AS WATER IMAGERY SHOWS SUBSIDENCE APPROACHING THE 
AREA AND PRESSURE GRADIENTS REMAIN STRONGLY OFFSHORE. ANOTHER STORM 
SYSTEM MOVING INTO THE PACNW WILL BRING A SURGE OF NORTH WINDS 
ACROSS THE MOUNTAINS LATER SUNDAY MORNING...THUS THE REASONING TO 
CONTINUE AN ADVISORY THROUGH SUNDAY NIGHT INTO MONDAY MORNING FOR 
THIS AREA. WILL NEED TO KEEP AN EYE ON THE ANTELOPE VALLEY AS WINDS 
THERE COULD ALSO REACH ADVISORY LEVELS TOMORROW AFTERNOON. WARMER 
TEMPERATURES WILL BE DELAYED UNTIL MONDAY DUE TO CONTINUED NORTHERLY 
WINDS ACROSS THE REGION. 

HIGH PRESSURE RIDGE BUILDS ACROSS THE WEST COAST LATER MONDAY AND 
TUESDAY. THIS RESULTS IN OFFSHORE WINDS AND WARMER TEMPERATURES 
EARLY NEXT WEEK. READINGS WILL BE WARMER IN ALL AREAS BY TUESDAY.

.LONG TERM (WED-SAT)...A WEAK SANTA ANA DEVELOPS LATE TUESDAY AND 
WEDNESDAY AS HIGH PRESSURE BUILDS OVER THE GREAT BASIN AND WEAK 
LOW PRESSURE DEVELOPS OVER WESTERN ARIZONA. OFFSHORE WINDS AND 
WARMER TEMPERATURES WILL CONTINUE AT LEAST THROUGH THURSDAY. MEDIUM 
RANGE MODELS BEGIN TO DIVERGE BY THIS POINT WITH THE ECMWF SHOWING A 
MORE PRONOUNCED LOW PRESSURE TROUGH MOVING ACROSS THE AREA ON 
FRIDAY. THE GFS MODEL IS SLOWER WITH THE TROUGH PASSAGE LATE NEXT 
WEEK...HOWEVER VERY LITTLE CHANCE OF PRECIPITATION IS INDICATED ON 
EITHER MODEL. A STRONGER OFFSHORE FLOW COULD DEVELOP OVER THE 
WEEKEND IF THE ECMWF RUN HANDLES THE DEVELOPMENT OF THE RIDGE OVER 
THE EASTERN PACIFIC OCEAN CORRECTLY. 

&&

.AVIATION...21/1800Z.

MID/UPPER LEVEL RIDGE OF HIGH PRES WILL BUILD OVER THE AREA. 
MODERATE UPPER LEVEL NORTHWEST WINDS WILL PREVAIL WHILE MODERATE MID 
LEVEL NORTH WINDS BECOME LIGHT TO MODERATE AFTER 22/03Z OVER AREA. A 
MODERATE NORTHERLY PRESSURE GRADIENT WILL BECOME MODERATE TO STRONG 
AFTER 22/06Z.  

KLAX...VERY LIKELY SCATTERED LOW CLOUDS WILL CLEAR EARLY. THERE IS A 
CHANCE VSBY WILL BECOME 5SM HZ AFTER 22/11Z AND PERSIST FOR SEVERAL 
HOURS. IT IS LIKELY LOW LEVEL NORTH WINDS WILL DEVELOP AND 
STRENGTHEN TO AROUND 10 KT AFTER 22/15Z AND PREVAIL FOR SEVERAL 
HOURS.  

KBUR...VERY LIKELY SCATTERED LOW CLOUDS WILL CLEAR EARLY. THERE IS A 
CHANCE VSBY WILL BECOME 5SM HZ AFTER 22/11Z AND THROUGH THE 
REMAINDER OF THE PERIOD.

VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS


&&

.LOX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY (SEE LAXNPWLOX).
GALE WARNING (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...BOLDT
AVIATION...30
SYNOPSIS...MEIER

WWW.WEATHER.GOV/LOSANGELES