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