Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000 FXUS66 KLOX 011134 AAA AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 430 AM PDT WED OCT 1 2014 ...UPDATED AVIATION DISCUSSION... .SYNOPSIS... A SIGNIFICANT WARMING TREND IS EXPECTED INTO THE WEEKEND AS SURFACE HIGH PRESSURE BUILDS INTO THE GREAT BASIN AND OFFSHORE FLOW STRENGTHENS THROUGH LATE THIS WEEK. WEAKER OFFSHORE FLOW IS EXPECTED FOR THE WEEKEND...BUT HOT AND DRY WEATHER WILL CONTINUE AS HIGH PRESSURE BUILDS ALOFT. COOLER WEATHER IS POSSIBLE EARLY TO MID NEXT WEEK. && .SHORT TERM (TODAY-FRI)...LATEST ACARS SOUNDING AROUND LAX INDICATED A STRENGTHENING INVERSION AROUND 1000 FT DEEP THIS MORNING. AN EDDY CIRCULATION HAS ALSO DEVELOPED ALLOWING FOR PATCHY LOW CLOUDS TO RANDOMLY DEVELOP ACROSS THE SOCAL BIGHT...ORANGE COUNTY AS WELL AS THE SOUTHERN PORTION OF THE SAN GABRIEL VALLEY. WITH THE INVERSION THIS DEEP AND THE EDDY CIRCULATION IN PLACE...EXPECT PATCHY LOW CLOUDS TO MOVE IN ACROSS THE LA COUNTY COAST...AND POSSIBLY PORTIONS OF THE SAN GABRIEL VALLEY. LESS CONFIDENT FOR STRATUS TO MAKE IT INTO VENTURA COUNTY AT THIS POINT. THERE WERE PATCHY LOW CLOUDS ACROSS THE SANTA BARBARA CENTRAL COAST AND SANTA YNEZ VALLEY. SOME PATCHY DENSE FOG WILL BE LIKELY FOR AREAS N OF POINT CONCEPTION THIS MORNING. SYNOPTICALLY...BROAD NW FLOW WILL CONTINUE OVER THE FORECAST AREA TODAY AS AN UPPER LEVEL HIGH STRENGTHENS TO ITS WEST OVER THE ERN PAC. BY THURSDAY THE UPPER RIDGE WILL PUSH INTO CALIFORNIA WITH THE UPPER HIGH PARKED OVER SOUTHERN AND CENTRAL CALIFORNIA. THIS PATTERN WILL PERSIST THROUGH AT LEAST SUNDAY BEFORE THE RIDGE BEGINS TO BREAKDOWN AS A WEAK UPPER TROUGH MOVES CLOSER TO CALIFORNIA FOR THE BEGINNING OF NEXT WEEK. AT THE LOWER LEVELS...A SURFACE HIGH WILL DEVELOP OVER NORTHERN NEVADA. THIS WILL CREATE A TIGHTENING OFFSHORE SURFACE GRADIENT OVER SOUTHERN CALIFORNIA BEGINNING TODAY...THEN STRENGTHEN ON THURSDAY MORNING. THE RESULTS WILL BE A SIGNIFICANT WARMING TREND ACROSS THE ENTIRE FORECAST AREA BY THURSDAY...WITH ADDITIONAL WARMING ACROSS THE COAST AND COASTAL VALLEYS AS WEAK TO MODERATE SANTA ANA WINDS CONTINUE INTO FRIDAY MORNING...THEN WEAKER EACH MORNING AFTER THAT THROUGH SUNDAY. FOR TODAY...THERE WILL BE WEAK OFFSHORE FLOW ACROSS THE INTERIOR SECTIONS INCLUDING THE MOUNTAINS AND ADJACENT WIND PRONE LA/VTU COUNTY VALLEY PASSES AND CANYONS. EXPECT MAX TEMPS TO BE A FEW DEGREES WARMER ACROSS THE INTERIOR TODAY...EXCEPT THE ANTELOPE VALLEY SHOULD LOWER A FEW DEGREES WITH THE OFFSHORE FLOW. THE TRICKY PART FOR TODAY WILL BE THE COASTAL TEMPS. A CATALINA EDDY DEVELOPED LAST NIGHT AND THE MARINE LAYER DEPTH WAS AROUND 1000 FT THIS MORNING...THIS SHOULD KEEP THE COASTAL TEMPS A TAD COOLER THIS MORNING BUT SHOULD WARM UP LATE THIS MORNING AS THE MARINE LAYER INFLUENCE MIXES OUT. TEMPS SHOULD BE SIMILAR OR A FEW DEGREES WARMER ACROSS THE LA/VTU COAST TODAY. AS THE UPPER HIGH MOVES OVERHEAD TONIGHT INTO THURSDAY...THE MARINE LAYER WILL BE VERY SHALLOW AND OFFSHORE WINDS WILL STRENGTHEN ACROSS THE LA/VTU COUNTY MOUNTAINS LATE THIS EVENING THEN SPREAD INTO THE WIND PRONE VALLEY AND COASTAL AREAS BY EARLY THURSDAY MORNING. LATEST NAM-WRF MODEL IS SUGGESTING THE LAX-DAG GRADIENT WILL BE AROUND -5.4MB BY 5 AM THU MORNING. THIS UPCOMING WIND EVENT IS MAINLY SURFACE GRADIENT DRIVEN. THERE WILL NOT BE MUCH UPPER SUPPORT TO DRIVE THE WINDS STRONGER AS THE UPPER HIGH WILL BE DIRECTLY OVER THE REGION. WIND ADVISORIES WILL LIKELY BE NEEDED FOR THE LA/VTU COUNTY MOUNTAINS...SANTA CLARITA VALLEY...VENTURA COUNTY VALLEYS AND POSSIBLY THE NW PORTION OF THE SAN FERNANDO VALLEY FOR THURSDAY MORNING. LATER SHIFTS WILL TAKE A LOOK AT THIS AS WE DRAW CLOSER TO THE FIRST SANTA ANA OF THE SEASON. NOT EXPECTING MUCH IN THE WAY OF LOW CLOUDS OVERNIGHT INTO THURSDAY MORNING AS GUSTY NE WINDS SHOULD SCOUR OUT ANY STRATUS. WITH THE WINDS EXPECTED TO BE STRONGER THURSDAY MORNING...EXPECT HIGH TEMPS TO RISE SIGNIFICANTLY ACROSS MANY COASTAL AREAS AS WELL AS THE COASTAL VALLEYS. WARMEST VALLEY LOCATIONS REACHING THE MID TO UPPER 90S. THE ANTELOPE VALLEY SHOULD BE EVEN COOLER ON THURSDAY WITH HIGHS ONLY IN THE LOWER TO MID 80S. THE STRONGEST WINDS WILL OCCUR THURDAY MORNING...WITH SLIGHTLY WEAKER WINDS EXPECTED ON FRIDAY MORNING. HIGHEST TEMPS OF THE WEEK ARE EXPECTED TO BE FRI AND SAT. FOR FRIDAY THERE WILL BE TRIPLE DIGIT READINGS ACROSS THE LA/VTU COUNTY COASTAL VALLEYS AND UP THE MID 90S ACROSS THE COASTAL PLAIN. ALTHOUGH WINDS WILL NOT BE AN ISSUE FOR THE SBA/SLO COUNTIES...THERE WILL BE SOME VERY WARM TEMPS ACROSS THE COASTAL AREAS AS WEAK OFFSHORE FLOW PERSISTS...ESPECIALLY THU-FRI. DONT BE SURPRISED TO SEE AVILA BEACH TO REACH 90 WITH SOME DOWNSLOPING EXPECTED ACROSS THE ADJACENT FOOTHILL. .LONG TERM (SAT-TUE)...AT THIS TIME...IT LOOKS LIKE SATURDAY WILL THE BE THE HOTTEST DAY OF THE WEEK WITH HIGH TEMPS BETWEEN 101-106 FOR THE LA/VTU COUNTY COASTAL VALLEYS AND THE UPPER 90S FOR DOWNTOWN LA AND LONG BEACH. THERE SHOULD BE A FEW DEGREES OF COOLING ON SUNDAY...BUT STILL VERY HOT. THE UPPER HIGH BEGINS TO BREAKDOWN AS A WEAK UPPER TROUGH APPROACHES CALIFORNIA. EXPECT TEMPERATURES TO REMAIN WELL ABOVE NORMAL THROUGH MONDAY...WITH SOME RELIEF POSSIBLE BY TUESDAY...ESPECIALLY ACROSS THE COASTAL AREAS AS NIGHT THROUGH MORNING LOW CLOUDS SHOULD AFFECT THE COASTAL AREAS. IT WILL REMAIN QUITE WARM THROUGH THE EXTENDED PERIOD...BUT NOT AS HOT AS THE WEEKEND. && .AVIATION...01/1130Z... MARINE LAYER AT KLAX AT 0815Z WAS 900 FEET DEEP AND THE INVERSION TOP WAS 2700 FEET WITH A TEMPERATURE OF 21 DEGREES C. OVERALL...MODERATE CONFIDENCE IN 12Z TAF PACKAGE. IN THE IMMEDIATE SHORT TERM...LOW CONFIDENCE IN MOST COASTAL TAF SITES DUE TO THE SOMEWHAT CHAOTIC NATURE OF THE STRATUS. ONCE THIS STRATUS CLEARS OUT BY LATE THIS MORNING...HIGH CONFIDENCE IN VFR CONDS PREVAILING THIS AFTERNOON THROUGH TONIGHT. KLAX...OVERALL...MODERATE CONFIDENCE IN 12Z TAF. LOW CONFIDENCE IN TAF FROM 12Z THRU 17Z AS THERE IS A 50% CHANCE THAT CIG RESTRICTIONS WILL NOT DEVELOP AS FORECAST. BEYOND 17Z...HIGH CONFIDENCE IN VFR CONDS PREVAILING THRU THE REMAINDER OF THE TAF PERIOD. KBUR...OVERALL...HIGH CONFIDENCE IN 12Z TAF. && .MARINE...01/200 AM... FOR THE OUTER WATERS...EXPECT NORTHWEST WINDS TO DIMINISH IN THE NEXT FEW HOURS...SO WILL LET THE SMALL CRAFT ADVISORIES EXPIRE AND WILL MENTION LOCAL GUST TO 25 KT THROUGH TODAY. FOR TONIGHT AND THROUGH THE WEEKEND...WINDS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. FOR THE INNER WATERS...HIGH CONFIDENCE IN WINDS REMAINING BELOW ADVISORY LEVELS THROUGH THIS EVENING. BY LATE TONIGHT AND THURSDAY HIGH CONFIDENCE IN NORTHEAST WINDS DEVELOPING WITH A CHANCE OF WINDS REACHING SMALL CRAFT ADVISORY THRESHOLDS THURSDAY MORNING (ESPECIALLY NEAR SHORE) FROM VENTURA TO MALIBU AND OUT TO THE ISLANDS. FOR FRIDAY THROUGH THE WEEKEND...WEAK OFFSHORE FLOW CAN BE EXPECTED AT NIGHT...AND WEAK ONSHORE FLOW IN THE AFTERNOON/EVENING HOURS. A LONG PERIOD SOUTH-SOUTHWEST SWELL IS ANTICIPATED TO ARRIVE ON WEDNESDAY AND CONTINUE THROUGH FRIDAY. && .FIRE WEATHER...CRITICAL FIRE WEATHER CONDITIONS ARE EXPECTED TO DEVELOP ACROSS MUCH OF VENTURA AND LOS ANGELES COUNTIES TONIGHT AS OFFSHORE GRADIENTS INCREASE AND HUMIDITIES FALL. NORTHEAST WINDS WILL ACTUALLY BEGIN AS EARLY AS THIS MORNING ACROSS THE MOUNTAINS VALLEYS, HOWEVER HUMIDITIES ARE EXPECTED TO REMAIN ABOVE 20 PERCENT IN MOST AREAS UNTIL TONIGHT WHEN MUCH DRIER AIR MOVES IN. THE STRONGEST WINDS ARE EXPECTED TONIGHT THROUGH EARLY AFTERNOON THURSDAY WITH GUSTS UP TO 40 MPH IN THE MOUNTAINS AND 25-30 MPH IN THE VALLEYS. HUMIDITIES THURSDAY WILL GENERALLY RANGE FROM 10-15 PERCENT. NORTHEAST WINDS ARE EXPECTED TO BE WEAKER THURSDAY NIGHT INTO FRIDAY BUT STILL REMAIN GUSTY AT TIMES. VERY POOR HUMIDITY RECOVERIES ARE EXPECTED THURSDAY NIGHT WITH WIDESPREAD SINGLE DIGIT HUMIDITIES FRIDAY THROUGH SUNDAY. && .LOX WATCHES/WARNINGS/ADVISORIES... FIRE WEATHER WATCH (SEE LAXRFWLOX). SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX). && $$ PUBLIC...KAPLAN AVIATION/MARINE...RAT FIRE...MW SYNOPSIS...SUKUP WWW.WEATHER.GOV/LOSANGELES

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