851 
FXUS66 KLOX 232254
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
345 PM PDT TUE OCT 23 2012

...UPDATED TO INCLUDE FIRE WEATHER SECTION...

.SYNOPSIS...
BREEZY NORTH WINDS MAY AFFECT SOME CANYON AREAS...INCLUDING THE I 
FIVE CORRIDOR...TONIGHT AND INTO WEDNESDAY MORNING. A RIDGE WILL 
BEGIN TO BUILD INTO THE AREA BRINGING GUSTY OFFSHORE WINDS AND 
WARMER TEMPERATURES BY LATE THURSDAY INTO THE WEEKEND.

&&

.SHORT TERM (TONIGHT-FRI)...
RESIDUAL MOISTURE GENERATING SOME STRATOCUMULUS CLOUDS ACROSS THE
MOUNTAINS AND INTERIOR VALLEYS THIS AFTERNOON. ANOTHER UPPER LEVEL IMPULSE
EXPECTED TO BRING A CHANCE OF RAIN TO NORTHERN AND CENTRAL CALIFORNIA
TONIGHT INTO WEDNESDAY MORNING...HOWEVER ALL MEASURABLE RAIN EXPECTED TO
REMAIN NORTH OF OUR FORECAST AREA. THE MAIN IMPACT OF THIS SYSTEM 
FOR US WILL BE INCREASING NORTH-SOUTH PRESSURE GRADIENTS. AS A 
RESULT...LOOKING FOR INCREASING NORTHERLY WINDS ACROSS THE 
INTERSTATE 5 CORRIDOR AND SANTA YNEZ RANGE...HOWEVER WINDS EXPECTED 
TO REMAIN BELOW ADVISORY LEVELS. 

FROM WEDNESDAY NIGHT INTO THURSDAY MORNING...THE NORTH-SOUTH PRESSURE
GRADIENTS WILL CONTINUE TO INCREASE WITH LAX-BAKERSFIELD GRADIENT EXPECTED
TO PEAK AT -7.2 MB AT 12Z THURSDAY. DURING THIS TIME...WE COULD SEE
WINDS RAMP UP TO ADVISORY LEVELS ACROSS THE I5 CORRIDOR IN THE LOS ANGELES
MOUNTAINS AND SANTA YNEZ RANGE...WITH GUSTS IN THE 40 TO 50 MPH 
RANGE. IN ADDITION...GUSTY NORTHERLY WINDS ARE ALSO EXPECTED TO EXPAND
INTO THE SANTA CLARITA VALLEY...SAN FERNANDO VALLEY...AND SANTA MONICA
MOUNTAINS...WHERE WIND ADVISORIES WITH GUSTS IN THE 30 TO 40 MPH 
RANGE WILL ALSO BE POSSIBLE.  THIS NORTHERLY WIND INFLUENCE WILL ALSO
BRING A GOOD WARMING TREND...ESPECIALLY ACROSS THE LOS ANGELES BASIN
WHERE TEMPERATURES WILL CLIMB ABOVE 80 DEGREES IN SOME LOCATIONS.

ON THURSDAY NIGHT INTO FRIDAY...SURFACE HIGH PRESSURE WILL BUILD ACROSS
THE GREAT BASIN...LIKELY BRINGING THE STRONGEST AND MOST WIDESPREAD SANTA
ANA EVENT OF THE SEASON. 12Z NAM SHOWING A RATHER IMPRESSIVE LAX-DAGGETT
GRADIENTS OF -8.2 MB FOR FRIDAY MORNING. IN ADDITION...CROSS 
SECTIONS SHOWING A LAYER OF 30-40 KNOT WINDS FROM THE SURFACE TO 850 MB
LEVEL WITH A GOOD SURGE OF SUBSIDENCE. AS A RESULT...THERE WILL BE THE
POTENTIAL FOR DAMAGING WIND GUSTS TO 60 MPH ACROSS THE MOUNTAINS OF
LOS ANGELES AND VENTURA COUNTIES...INCLUDING THE SANTA MONICA 
MOUNTAINS. AS A RESULT...HIGH WIND WATCHES HAVE BEEN POSTED FOR THESE
AREAS. IN ADDITION...WIDESPREAD WIND GUSTS IN THE 40 TO 50 MPH RANGE 
WILL BE LIKELY FOR COASTAL AND VALLEY AREAS OF LOS ANGELES AND 
VENTURA COUNTIES...WHERE WIND ADVISORIES WILL LIKELY BE NEEDED AS WE 
DRAW CLOSER TO THE EVENT. OFFSHORE WINDS ARE EXPECTED TO RAMP UP 
QUICKLY THURSDAY EVENING ACROSS THE MOUNTAINS AND VALLEYS...PEAKING
IN STRENGTH LATE THURSDAY NIGHT INTO FRIDAY. THE GUSTY NORTHEAST WINDS
WILL ALSO COINCIDE WITH LOW HUMIDITIES AND CRITICALLY DRY FUELS TO
BRING A SIGNIFICANT FIRE WEATHER CONCERN TO THE REGION. FIRE WEATHER WATCHES
HAVE ALREADY BEEN POSTED FROM THURSDAY NIGHT THROUGH FRIDAY EVENING FOR
THE MUCH OF LOS ANGELES AND VENTURA COUNTIES. 

PLEASE REFER TO FIRE SECTION BELOW FOR MORE DETAILS.

.LONG TERM (SAT-TUE)...
WEAK OFFSHORE FLOW WILL CONTINUE TO REINFORCE VERY WARM AND DRY
CONDITIONS FOR THE WEEKEND. WHILE OFFSHORE WINDS WILL NOT BE AS
STRONG AS FRIDAY...THERE WILL CONTINUE TO BE SOME HEIGHTENED FIRE
WEATHER CONCERNS FOR THE WEEKEND. BY TUESDAY...LONG RANGE MODELS
SHOWING A RETURN OF ONSHORE FLOW FOR THE BEGINNING OF A COOLING
TREND.

&&

.FIRE...GUSTY NORTHERLY WIND EXPECTED TO INCREASE IN COVERAGE AND 
AREAL INTENSITY FROM WEDNESDAY NIGHT THROUGH THURSDAY MORNING. THE 
STRONGEST NORTHERLY WINDS WILL BE FOCUSED ACROSS THE INTERSTATE 5 
CORRIDOR IN THE LOS ANGELES COUNTY MOUNTAINS AND SANTA YNEZ 
RANGE...WITH GUSTS IN THE 40 TO 50 MPH RANGE. THE NORTHERLY WINDS 
ARE ALSO EXPECTED TO IMPACT THE SANTA CLARITA VALLEY...SAN FERNANDO 
VALLEY...AND SANTA MONICA MOUNTAINS...WITH GUSTS IN THE 30 TO 40 MPH 
RANGE. HUMIDITIES ARE EXPECTED TO LOWER TO BETWEEN 10 AND 15 
PERCENT...WITH SOME PORTIONS OF LOS ANGELES COUNTY BRIEFLY LOWERING 
INTO SINGLE DIGITS. AS A RESULT...BRIEF CRITICAL FIRE WEATHER 
CONDITIONS CAN BE EXPECTED FOR PORTIONS OF LOS ANGELES COUNTY AS 
WELL AS THE SANTA YNEZ RANGE...HOWEVER DURATIONS ARE NOT 
SUFFICIENTLY LONG TO WARRANT A RED FLAG WARNING AT THIS TIME. 

THE GUSTY NORTHERLY WINDS WILL HELP TO PRIME THE ALREADY DRY FUELS 
ACROSS THE REGION. WINDS ARE EXPECTED TO SHIFT TO THE NORTHEAST BY 
THURSDAY NIGHT...WITH THE STRONGEST AND MOST WIDESPREAD SANTA ANA 
WIND EVENT EXPECTED SO FAR THIS SEASON. FIRE WEATHER WATCHES HAVE 
ALREADY BEEN POSTED FOR MUCH OF VENTURA AND LOS ANGELES COUNTIES FROM
THURSDAY NIGHT THROUGH FRIDAY EVENING. THE STRONGEST WINDS WILL 
LIKELY OCCUR LATE THURSDAY NIGHT THROUGH FRIDAY IN THE MOUNTAINS OF 
LOS ANGELES AND VENTURA COUNTIES...WHEN GUSTS IN THE 50 TO 60 MPH 
RANGE WILL BE POSSIBLE. HOWEVER...OFFSHORE WINDS GUSTING TO BETWEEN 
40 AND 50 MPH CAN BE EXPECTED ACROSS COASTAL AND VALLEY AREAS AS 
WELL. HUMIDITY LEVELS WILL GENERALLY RANGE BETWEEN 10 AND 20 PERCENT 
FROM THURSDAY NIGHT THROUGH EARLY FRIDAY MORNING...THEN LOWER TO 
BETWEEN 5 AND 10 PERCENT ACROSS MUCH OF THE WATCH AREA FRIDAY 
AFTERNOON INTO FRIDAY EVENING. IF FIRE IGNITION OCCURS...THIS SANTA 
ANA WIND EVENT WILL HAVE THE POTENTIAL TO BRING RAPID SPREAD OF 
WILDFIRE DUE TO CRITICAL FIRE WEATHER CONDITIONS AND CRITICALLY DRY 
FUELS.

&&

.AVIATION...23/1800Z.
MOSTLY VFR CONDITIONS ARE EXPECTED THROUGH WEDNESDAY ASIDE FROM THE 
OCCASIONAL MVFR TO VFR CEILING CAUSED BY WEAK FRONTAL ACTIVITY UP 
NEAR THE MONTEREY BORDER. OF GREATER CONSEQUENCE WILL BE THE GRADUAL 
INCREASE IN NORTH WINDS OVER THE NEXT 24 HOURS AS NORTHERLY FLOW 
WILL ACCELERATE THROUGH THE PASSES AND CANYONS OF THE SANTA YNEZ 
MOUNTAINS AND THROUGH THE I-5 CORRIDOR IN NORTHWEST LOS ANGELES 
COUNTY. THEREFORE...LOCAL WIND SHEAR AND TURBULENCE MAY AFFECT KSBA 
THIS EVENING AND POSSIBLY KBUR AND KVNY BY WEDNESDAY NIGHT NOT TO 
MENTION AN OUTSIDE CHANCE OF CROSS-WINDS AT KLAX WEDNESDAY NIGHT.

KLAX...MVFR TO VFR CEILINGS ARE OCCASIONALLY POSSIBLE DUE TO 
LINGERING MOISTURE IN THE LA BASIN. OTHERWISE VFR CONDITIONS WILL 
CONTINUE THROUGH WEDNESDAY. THERE IS A SLIGHT CHANCE OF NORTHERLY 
CROSS-WINDS WEDNESDAY NIGHT.

KBUR...MVFR TO VFR CEILINGS ARE OCCASIONALLY POSSIBLE DUE TO 
LINGERING MOISTURE IN THE LA BASIN. OTHERWISE VFR CONDITIONS WILL 
CONTINUE THROUGH WEDNESDAY. THERE IS A SLIGHT CHANCE OF LOW LEVEL 
WIND SHEAR AND TURBULENCE WEDNESDAY NIGHT DUE TO INCREASING 
NORTHERLY FLOW.

&&

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

&&

$$

PUBLIC...GOMBERG/KJ
AVIATION...SWEET
FIRE...GOMBERG
SYNOPSIS...BARTLING

WWW.WEATHER.GOV/LOSANGELES