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000 FXUS66 KLOX 150416 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 915 PM PDT SUN SEP 14 2008 .SHORT TERM (TONIGHT-WED)...LAX ACARS SOUNDINGS SHOWING THE MARINE INVERSION HAS LOWERED TO AROUND 950 FT...WITH WARMING TO 84 DEG F AROUND 2500 TO 2600 FT. TEMPERATURES AT SOME FOOTHILL LOCATIONS LIKE MALIBU HILLS REMAINED IN THE LOWER 80S AS OF 830 PM. GRADIENTS HAVE CONTINUED TO TREND OFFSHORE OVER THE REGION AS WELL. IT LOOKS LIKE WARM TEMPS SHOULD PREVAIL AT THE FOOTHILL AREAS OVERNIGHT. MARINE LAYER CLOUDS THIS EVENING WERE NOT VERY ORGANIZED WITH PATCHY LOW CLOUDS ALONG THE CENTRAL COAST AND JUST OFF THE PALOS VERDES PENINSULA. LOW CLOUDS SHOULD EXPAND SOME ALONG THE CENTRAL COAST OVERNIGHT BUT REMAIN RATHER PATCHY S OF POINT CONCEPTION. LOCAL DENSE FOG WILL BE POSSIBLE ESPECIALLY ALONG THE CENTRAL COAST. OTHERWISE SKIES WILL BE MOSTLY CLEAR THRU THE NIGHT OVER THE FORECAST AREA. AN UPPER HIGH OVER NEVADA AND OREGON WILL BUILD INTO THE NORTHERN GREAT BASIN ON MON AND E INTO COLORADO FOR TUE AND WED. AN UPPER LOW SEVERAL HUNDRED MILES OFF THE CENTRAL CA COAST WILL MOVE E TOWARD THE COAST THRU MON THEN BEGIN TO WEAKEN AND OPEN UP INTO AN UPPER TROF MON NIGHT AND TUE AS IT MOVES TO THE CENTRAL AND NRN CA COAST. A FLAT UPPER RIDGE CAN BE EXPECTED OVER SRN CA FOR WED. THE MID LEVEL FLOW OVER THE FORECAST AREA WILL BE GENERALLY SE TO S THRU TUE...THEN TURN WESTERLY FOR WED. THE LATEST WRF IS FORECASTING DECENT AMOUNTS OF MID LEVEL MOISTURE MOVING INTO THE REGION ON TUE. WITH SOME INSTABILITY IT LOOKS LIKE THERE WILL BE AT LEAST SOME AFTERNOON CU BUILDUPS IN THE MOUNTAINS...AND THE POSSIBILITY OF SOME THUNDERSTORM DEVELOPMENT CANNOT BE RULED OUT AS WELL. FOR NOW WILL INTRODUCE A 10 PERCENT CHANCE OF PCPN TO THE MTNS FOR TUE IN THE GRIDS. LATER SHIFTS WILL HAVE TO MONITOR ADDITIONAL MODEL RUNS TO FINE TUNE THE FORECAST. THE MARINE LAYER IS EXPECTED TO REMAIN SHALLOW THRU TUE AS THE BOUNDARY LAYER CONTINUES TO WARM UP AND GRADIENTS TREND OFFSHORE WITH TIME. PATCHY NIGHT AND MORNING LOW CLOUDS AND FOG WILL AFFECT THE COASTAL AREAS THRU TUE MORNING. THE MARINE LAYER SHOULD BECOME A BIT BETTER ORGANIZED TUE NIGHT INTO WED WITH BETTER COVERAGE OF THE LOW CLOUDS MAINLY OVER THE COASTAL PLAIN. HI TEMPS ARE EXPECTED TO WARM TO WELL ABOVE NORMAL FOR MANY INLAND AREAS MON AND TUE...WITH THE WARMEST VALLEYS REACHING INTO THE LOW 100S...THEN COOL BACK SOME TO SLIGHTLY ABOVE NORMAL FOR WED. OVERNIGHT LOWS WILL REMAIN VERY MILD IN THE FOOTHILLS THRU MON NIGHT...WITH SOME LOCATIONS REMAINING IN THE 70S. AN EXTENDED PERIOD OF HUMIDITIES BELOW 10 PERCENT IN THE MOUNTAINS IS EXPECTED LATER TONIGHT THRU EARLY TUE EVENING. A RED FLAG WARNING IS IN EFFECT FOR THE MOUNTAINS OF L.A./VTU/SBA COUNTIES...AND A FIRE WEATHER WATCH IS IN EFFECT FOR THE SLO COUNTY MTNS. PLEASE SEE LAXRFWLOX FOR DETAILS. ...FROM PREVIOUS DISCUSSION... .LONG TERM (THU-SUN)...COOLING TREND TO CONTINUE THROUGH THURSDAY BRINGING DAYTIME HIGHS DOWN TO NEAR NORMAL LEVELS. THEN LITTLE CHANGE EXPECTED FRIDAY. OVER THE WEEKEND THE TROF FINALLY MOVES INLAND THROUGH THE PAC NW AND HEIGHTS/THICKNESSES RISE SLIGHTLY ACROSS SRN CA. ONSHORE FLOW ALSO WEAKENS, ESPECIALLY BY SUNDAY SO WE COULD SEE A FEW DEGREES OF WARMING NEXT WEEKEND. FOR NOW THOUGH CONFIDENCE ISN`T HIGH ENOUGH TO GO AGAINST PERSISTENCE SO WILL STICK WITH SIMILAR CONDITIONS THROUGH THE WEEKEND. && .AVIATION...14/2340Z...MARINE LAYER HAS FALLEN TO NEAR 1200 FT DEEP AT KLAX. WITH THE MARINE LAYER EXPECTED TO CONTINUE LOWERING SOME OVERNIGHT IT LOOKS LIKE LOW CLOUDS SHOULD NOT MOVE INTO THE VALLEY TAF SITES TONIGHT AND MON. IT LOOKS LIKE MODERATE CONFIDENCE THAT LOW CLOUDS AND IFR TO LIFR CONDITIONS WILL EVENTUALLY MOVE BACK INTO MOST COASTAL TAF SITES TONIGHT. THE TIMING IS PROBLEMATIC CONSIDERING THE CLEARING PATTERN OF THE LOW CLOUDS THIS AFTERNOON OFF THE CENTRAL COAST AND THE CLEARING TREND ALONG THE COAST S OF POINT CONCEPTION. OVERALL...MOST COASTAL TAF SITES SHOULD HAVE THE LOW CLOUDS AND FOG MOVE IN FROM ABOUT 05Z TO 07Z. THE LOW CLOUDS AND FOG WITH IFR AND SOME LIFR CONDITIONS WILL PREVAIL UNTIL ABOUT 16Z TO 17Z MON...THEN VFR CONDITIONS SHOULD DEVELOP FROM LATER MON MORNING THRU THE AFTERNOON. MODERATE TO HI CONFIDENCE THE TAF SITES AWAY FROM THE COAST WILL HAVE VFR CONDITIONS THRU MON. FOR KLAX...MODERATE CONFIDENCE IFR CIGS WILL MOVE INTO THE AIRFIELD AROUND 06Z...BUT COULD BE DELAYED UNTIL 07Z OR 08Z. THE LOW CLOUDS WILL CLEAR OFF THE COAST TO VFR CONDITIONS BY ABOUT 16Z MON...THEN CLEAR CONDITIONS WILL PREVAIL THRU MON AFTERNOON. NO WIND ISSUES EXPECTED THRU MON. FOR KBUR...MODERATE CONFIDENCE VFR CONDITIONS WILL PREVAIL THROUGH MON. NO WIND ISSUES ARE EXPECTED THRU THE PERIOD. && .LOX WATCHES/WARNINGS/ADVISORIES... RED FLAG WARNING (SEE LAXRFWLOX). FIRE WEATHER WATCH (SEE LAXRFWLOX). SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...SIRARD/WOFFORD AVIATION...SIRARD WWW.WEATHER.GOV/LOSANGELES