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