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000 FXUS66 KLOX 170328 AFDLOX SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA 830 PM PDT TUE SEP 16 2008 .SHORT TERM (TODAY-FRI)... TEMPERATURES WERE DOWN TODAY OVER MUCH OF THE SOUTHLAND THIS AFTERNOON. MOSTLY DUE TO MID LEVEL MOISTURE THAT BROUGHT ALTOCU ACROSS MOSTLY LA COUNTY. HOWEVER...SOUTHERLY FLOW ACROSS THE LA COASTAL AREAS ALSO CONTRIBUTED TO SOME OF THE COOLING. WITH THE AFTERNOON HEATING ACROSS THE LA COUNTY MOUNTAINS AND THE ANTELOPE VALLEY...A FEW SHOWERS POPPED UP LATE THIS AFTERNOON. NOT MUCH VERTICAL DEVELOPMENT WITH THESE STORMS...AS BETTER CONVECTIVE PARAMETERS WERE FARTHER EAST OVER SAN BERNARDINO COUNTY. WITH THE HEATING OF THE AFTERNOON NOW GONE...SO ARE THE FEW SHOWERS THAT OCCURRED. LATEST AMDAR SOUNDING NEAR KLAX INDICATED THE MARINE LAYER NEAR 1000 FT DP THIS EVENING. LATEST FOG PRODUCT IS SHOWING THE DEVELOPMENT OF STRATUS OFF THE LA/ORANGE COUNTY COAST. SINCE THE OUTER WATERS HAD GALE FORCE WINDS LAST NIGHT...WITH SMALL CRAFT WINDS CONTINUING TODAY...A CATALINA EDDY WILL DEVELOP OVERNIGHT HELPING TO DEEPEN THE MARINE LAYER TO NEAR 1500 FT LATER. SFC GRADS ARE CURRENTLY TRENDING ONSHORE AND SHOULD HELP PUSH LOW CLOUDS INTO THE COASTAL VALLEYS OF LA/VTU COUNTIES OVERNIGHT. THE WEAK NEGATIVE TILTED TROF OVER NRN/CNTRL CAL WILL PUSH TO THE NE OVERNIGHT. THIS WILL BRING A SLIGHT INCREASE IN 500 MB HEIGHTS. THICKNESS LVLS DONT CHANGE MUCH. THEREFORE...TEMPS SHOULD REBOUND TO THE MID 90S ACROSS THE INTERIOR VALLEYS WHILE COASTAL AREAS SHOULD BE A TAD COOLER S OF POINT CONCEPTION AS A STRONGER MARINE INFLUENCE WILL BE LIKELY. HOWEVER...THERE IS A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS FOR THE LA/VTU COUNTY MTNS AND THE ANTELOPE VALLEY ONCE AGAIN WEDNESDAY AFTERNOON AS PWAT VALUES JUMP UP TO NEAR 1.5 INCHES. ONCE AGAIN...NOT TOO IMPRESSED WITH CONVECTIVE PARAMETERS FOR OUR AREA AS 700-500 MB WIND DIRECTION IS MORE SOUTHERLY THAN SOUTHEASTERLY...LIFTED INDEX NEAR -1...HOWEVER K-INDEX VALUES ARE BETWEEN 30-38 WHICH IS A BIT IMPRESSIVE FOR OUR AREA. NEVERTHELESS...WITH BETTER MID LEVEL MOISTURE AVAILABLE...SLIGHT CHANCE WORDING SEEMS REASONABLE. ...FROM PREVIOUS DISCUSSION... SLIGHT COOLING ON THURSDAY AS YET ANOTHER TROF APPROACHES NRN CA. THE UPPER LOW ASSOCIATED WITH THE TROF IS EXPECTED TO OVER SFO FRI SO DAYTIME HIGHS SHOULD DROP ANOTHER FEW DEGREES. MARINE LYR WILL DEEPEN AND SPREAD INTO THE VALLEYS OVERNIGHT. .LONG TERM (SAT-TUE)...NO HUGE CHANGES ARE EXPECTED AT LEAST THROUGH MONDAY. SLIGHT WARMING EXPECTED BY SUNDAY AS THE TROF MOVES EAST AND HEIGHTS RISE OVER THE AREA. BY MON BOTH THE ECMWF AND GFS SHOW A DEEPER TROF SETTING UP OVER THE WEST COAST. HOWEVER, ON TUE THE GFS IS MUCH DEEPER AND COOLER WHILE THE ECMWF MOVES THE TROF EAST INTO THE NRN ROCKIES. ENSEMBLES ALSO SHOW A FAIRLY LARGE RANGE OF SOLUTIONS SO FOR NOW HAVE INDICATED LITTLE CHANGE FOR TUE AS IT`S TOO SOON TO PLAY FAVORITES. && .AVIATION...16/1935Z. ODD SITUATION OF BKN CONDITIONS AT KLGB WILL GO AWAY WITHIN THE HOUR. OTHERWISE MOSTLY CLEAR SKIES ACROSS THE REGION THIS AFTERNOON. GOOD CONFIDENCE IN LOW CLOUDS AND FOG WITH IFR CONDITIONS RETURNING LATE TONIGHT TO ALL COASTAL TAFS EXCEPT KSBA WHICH WILL REMAIN CLEAR THROUGH THE NIGHT. POSSIBLE DIFFICULTY WITH LLWS IN KSBA THIS EVENING DUE TO GUSTY WINDS BELOW PASSES AND CANYONS. KLAX...GOOD CONFIDENCE IN CLEAR SKIES THROUGH THE EVENING FOLLOWED BY A RETURN OF LOW CLOUDS AND FOG WITH IFR CONDITIONS AFTER MIDNIGHT. A 30 PERCENT CHANCE OF LOW CLOUDS AND FOG MOVING IN SOONER THAN DEPICTED BY THE CURRENT TAF...PERHAPS BY 05Z. KBUR...VERY HIGH CONFIDENCE...NEAR 100 PERCENT CHANCE...IN CLEAR SKIES AND UNRESTRICTED VISIBILITY THROUGH WEDNESDAY. && .LOX WATCHES/WARNINGS/ADVISORIES... SMALL CRAFT ADVISORY (SEE LAXMWWLOX). && $$ PUBLIC...KAPLAN/WOFFORD AVIATION...SWEET WWW.WEATHER.GOV/LOSANGELES