000 
FXUS66 KLOX 030338
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
840 PM PDT SAT MAY 2 2009

.SHORT TERM (TONIGHT-TUE)...DIRTY FLAT UPPER LEVEL RIDGE OVER THE 
REGION WITH PLENTY OF HI CLOUDS MOVING THRU. THERE WERE ALSO SOME 
LOW CLOUDS ALONG THE IMMEDIATE CENTRAL COAST...OVER PORTIONS OF THE 
L.A. COUNTY COASTAL PLAIN...AND FROM THE SAN GABRIEL VALLEY TO THE 
ADJACENT COASTAL SLOPES OF THE SAN GABRIEL MTNS. OVERNIGHT...VARYING 
AMOUNTS OF LOW CLOUDS ARE EXPECTED TO PERSIST IN THESE AREAS. 
OTHERWISE SKIES WILL BE PARTLY CLOUDY THRU THE NIGHT WITH MORE HI 
CLOUDS MOVING OVERHEAD. GUSTY W WINDS OVER 30 MPH IN SOME PARTS OF 
THE ANTELOPE VALLEY EARLY THIS EVENING WILL DIMINISH SOME OVERNIGHT.

FLAT UPPER RIDGE IS EXPECTED TO LINGER OVER SRN CA THRU TUE WHILE A 
COUPLE OF WEAK UPPER DISTURBANCES MOVE JUST TO THE NORTH OF THE 
DISTRICT IN A BROAD W TO WNW FLOW ALOFT. THE FIRST WEAK UPPER 
DISTURBANCE MAY BRING A FEW SHOWERS TO THE FAR NWRN SLO COUNTY COAST 
ON SUN. OTHERWISE...ONLY SOME CLOUDS WILL AFFECT MAINLY NORTHERN 
PARTS OF THE DISTRICT FROM THE WEAK DISTURBANCES ON SUN AND AGAIN 
LATE SUN NIGHT INTO MON. IT ALSO LOOKS LIKE VARYING AMOUNTS OF 
MARINE LAYER LOW CLOUDS WILL AFFECT MAINLY COASTAL AREAS NIGHT AND 
MORNING HOURS THRU TUE....EXCEPT ALONG THE SBA S COAST WHERE GUSTY 
NORTHERLY CANYON WINDS EACH EVENING SHOULD KEEP THE LOW CLOUDS AWAY. 
GUSTY W TO NW WINDS WILL AFFECT THE CENTRAL COAST AND ANTELOPE 
VALLEY AND GUSTY NW TO N WINDS WILL AFFECT THE L.A./VTU MTNS 
ESPECIALLY ALONG THE I-5 CORRIDOR PRETTY MUCH EACH AFTERNOON AND 
EVENING THRU TUE AS WELL. TEMPS WILL BE SLIGHTLY ABOVE NORMAL MOST 
AREAS SUN AND MON...THEN A FEW DEGREES MORE ABOVE NORMAL FOR TUE AS 
WE HEAD INTO A WARMING TREND.   

...FROM PREVIOUS DISCUSSION...

.LONG TERM (WED-SAT)...GFS AND ECMWF IN FAIRLY GOOD AGREEMENT ON 
WEDNESDAY AND THURSDAY...WITH UPPER LEVEL RIDGING BUILDING ACROSS 
THE AREA...LEADING TO HIGHER THICKNESS VALUES ACROSS THE REGION. AT 
LOWER LEVELS...A TIGHT NORTHWEST PRESSURE GRADIENT IS EXPECTED TO 
PREVAIL...WHICH WILL HELP TO REINFORCE GUSTY SUNDOWNER WINDS IN THE 
VICINITY OF PASSES AND CANYONS IN SOUTHERN SBA COUNTY AS WELL AS THE 
TYPICAL NORTHWEST WINDS IN THE I5 CORRIDOR IN THE LA COUNTY 
MOUNTAINS. MORE SUBSTANTIAL WARMING EXPECTED TO TAKE PLACE ACROSS 
THE REGION ON WEDNESDAY AND THURSDAY...ESPECIALLY INLAND AREAS. 
WARMEST VALLEY...MOUNTAIN...AND DESERT LOCATIONS EXPECTED TO SOAR 
INTO THE 90S DURING THIS PERIOD. WITH THE WARMING AIR MASS...COULD 
SEE SOME VERY WARM READINGS IN THE SBA AREA AS WELL IF THE GUSTY 
SUNDOWNER WINDS MATERIALIZE.

THE GFS BEGINS TO FLATTEN THE RIDGE MUCH QUICKER ON FRIDAY...WITH 
BOTH GFS AND ECMWF RETURNING TO A MORE ZONAL FLOW PATTERN WITH 
STRONGER ONSHORE FLOW ON SATURDAY. HAVE GONE WITH A GRADUAL COOLING 
TREND FOR FRIDAY INTO SATURDAY...BUT COULD BE MORE DRAMATIC IF GFS 
SOLUTION WERE TO VERIFY. 

&&

.AVIATION...03/0320Z...MODERATE TO HI CONFIDENCE IFR TO LOW MVFR 
CIGS WILL AFFECT MOST COASTAL TAF SITES OVERNIGHT INTO SUN MORNING. 
OTHERWISE GENERALLY VFR CONDITIONS CAN BE EXPECTED ACROSS THE REGION 
THRU SUN. GUSTY W TO NW MAINLY AFTERNOON WINDS CAN BE EXPECTED FOR 
THE ANTELOPE VALLEY AND CENTRAL COAST AS WELL.

FOR KLAX...HI CONFIDENCE IFR TO LOW MVFR CIGS WILL AFFECT THE 
AIRFIELD OVERNIGHT INTO SUN MORNING...THEN VFR CONDITIONS CAN BE 
EXPECTED FROM LATE SUN MORNING THRU SUN EVENING. NO WIND ISSUES ARE 
EXPECTED.

FOR KBUR...VERY LOW CONFIDENCE MVFR CIGS WILL AFFECT THE AIRFIELD 
OVERNIGHT SO WENT WITH VFR CONDITIONS THRU SUN. NO WIND ISSUES ARE 
EXPECTED. 

&&

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

&&

$$

PUBLIC...SIRARD/GOMBERG
AVIATION...SIRARD

WWW.WEATHER.GOV/LOSANGELES