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