188 
FXUS66 KLOX 151227
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
530 AM PDT SAT SEP 15 2012

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...
UPPER LEVEL HIGH PRESSURE AND WEAK OFFSHORE FLOW WILL MAKE FOR 
ANOTHER VERY HOT DAY TODAY. A WEAK TROUGH DROPPING SOUTHEASTWARD 
THROUGH THE PACIFIC NORTHWEST WILL BRING SOME COOLING TO THE REGION 
SUNDAY AND MONDAY WITH MORE WIDESPREAD NIGHT THROUGH MORNING CLOUDS 
IN COASTAL AREAS. ANOTHER WARMING TREND IS POSSIBLE STARTING 
WEDNESDAY AS THE UPPER RIDGE IS EXPECTED TO REBUILD. 
 
&&

.SHORT TERM (TODAY-MON)...WITH THE EXCEPTION OF SOME LOW CLOUDS AND 
LOCALLY DENSE FOG ON THE CENTRAL COAST...SKIES WERE CLEAR ACROSS THE 
REGION. GRADIENTS BETWEEN KLAX AND KDAG WERE NEARLY IDENTICALLY 
OFFSHORE TO THOSE AT THIS TIME ON FRI. LOCALLY GUSTY WINDS WERE 
PRESENT AGAIN IN THE MTNS...BUT WERE SLIGHTLY WEAKER THAN THOSE FRI 
MORNING. PROFILER DATA ACTUALLY SHOWS A FEW MORE DEGREES OF WARMING 
BELOW 1000 FEET...WITH LITTLE CHANGE ABOVE THAT. EXPECT ANOTHER VERY 
HOT DAY TODAY...WITH TEMPS VERY SIMILAR TO THOSE REACHED ON FRI IN 
MOST AREAS. SOME LOCATIONS COULD EVEN BE A COUPLE OF DEGREES 
WARMER...ESPECIALLY ACROSS INTERIOR SECTIONS OF THE COASTAL PLAIN.
THERE COULD ALSO BE SOME WARMING ACROSS INTERIOR SECTIONS OF THE 
CENTRAL COAST AS MODELS SHOW SOME WEAK LOW LVL NELY FLOW THERE THIS 
MORNING. HOTTEST LOCATIONS ON THE L.A. COUNTY COASTAL PLAIN SHOULD 
AGAIN HAVE TEMPS NEAR OR A FEW DEGREES ABOVE THE CENTURY 
MARK...WHILE VIRTUALLY ALL VALLEY LOCATIONS WILL HAVE MAX TEMPS 
ABOVE 100 DEGREES TODAY.

A WEAK POSITIVELY TILTED TROUGH WILL DROP SEWD THRU THE PAC NW 
TONIGHT AND SUNDAY...AND THE UPPER HIGH OVER THE REGION WILL WEAKEN 
AND FLATTEN OUT. THE WRF STILL INDICATES VERY LITTLE IN THE WAY OF 
STRATUS TONIGHT/SUN MORNING...CONFINED MAINLY TO THE CENTRAL COAST. 
GRADS FLIP ONSHORE ACROSS THE REGION SUNDAY AFTERNOON. THERE SHOULD 
BE SEVERAL DEGREES OF COOLING IN MOST AREAS ON SUNDAY DUE TO THE 
ONSHORE GRADIENTS...COOLING AT 850 MB AND 950 MB AND FALLING 
THICKNESSES. HOTTEST LOCATIONS IN THE VALLEYS COULD GET CLOSE TO 100 
DEGREES. HOWEVER...THE 06Z RUN OF THE WRF ACTUALLY SHOWS A BIT MORE 
IN THE WAY OF COOLING FOR SUNDAY...SO TEMPS IN THE FCST COULD BE A 
TOUCH TOO HIGH. 

HEIGHTS/THICKNESSES FALL A BIT MORE SUN NIGHT/MON AND ONSHORE GRADS 
INCREASE A BIT MORE. EXPECT A RETURN TO NIGHT THRU MORNING LOW 
CLOUDS/FOG IN MOST COASTAL AREAS...AND THERE SHOULD BE A FEW MORE 
DEGREES OF COOLING ON MON. HOWEVER...TEMPS WILL LIKELY STILL BE 
NEAR NORMAL OR POSSIBLY EVEN STILL A BIT ABOVE NORMAL IN MOST 
AREAS. 


LONG TERM (TUE-FRI)...EXPECT MOSTLY MINOR CHANGES FOR TUE AND WED AS 
HEIGHTS/THICKNESSES CHANGE LITTLE AND UPPER RIDGE REMAINS TO THE E 
OF THE REGION. SOME WARMING MAY TAKE PLACE FOR THU AND FRI AS THE 
RIDGE TRIES TO REBUILD ACROSS THE REGION. HOWEVER...THE LATEST RUN 
OF THE GFS IS NOT AS AGGRESSIVE AS PREVIOUS RUNS...SO THE TEMP 
FORECAST FOR THE END OF THE WEEK IS A RATHER LOW CONFIDENCE ONE. 

&&

.FIRE WEATHER...IT HAS REMAINED VERY WARM AND DRY IN THE FOOTHILLS 
AND MOUNTAINS EARLY THIS MORNING...WITH POOR HUMIDITY RECOVERIES. 
WHILE OFFSHORE WINDS WILL BE WEAKER TODAY...THERE WILL 
CONTINUE TO BE ELEVATED FIRE DANGER ACROSS MUCH OF SOUTHERN 
CALIFORNIA DUE TO CONTINUED VERY HIGH TEMPERATURES AND LOW 
HUMIDITIES ALONG WITH CRITICALLY DRY FUELS. SEVERAL AREAS WILL ONCE 
AGAIN SEE HUMIDITIES FALL INTO SINGLE DIGITS ON TODAY...ESPECIALLY 
FOOTHILL AND MOUNTAIN LOCATIONS. SLIGHT COOLING TREND AND HUMIDITY 
RECOVERY CAN BE EXPECTED ON SUNDAY...WITH BETTER COOLING BY MONDAY.

&&
 
.AVIATION...15/1230Z
N OF POINT CONCEPTION...HIGH CONFIDENCE THROUGH 04Z THIS 
EVENING. EXPECT LIFR CONDS FOR THE CENTRAL COAST THROUGH 18Z. 30 
PERCENT CHANCE FOR STRATUS TO DISSIPATE +/- 1 HOUR FROM SUGGESTED 
TAF TIMES. AFTER 04Z LOW CONFIDENCE FOR LIFR CONDS TO RETURN BETWEEN 
06Z-016Z. 40 PERCENT CHANCE LIFR CIGS WILL NOT AFFECT CENTRAL COAST 
UNTIL 09Z. HIGH CONFIDENCE FOR KPRB TO REMAIN VFR OVER THE NEXT 24 
HOURS. 
S OF POINT CONCEPTION...HIGH CONFIDENCE WITH 12Z TAF FOR VFR CONDS 
OVER THE NEXT 24 HOURS. 10 PERCENT CHANCE FOR LIFR CIGS ALONG LA 
COUNTY COAST BETWEEN 10Z-16Z SUN.

KLAX/KBUR...HIGH CONFIDENCE WITH 12Z TAFS. EXPECT CAVU CONDITIONS 
OVER NEXT 24 HOURS. 

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&

$$

PUBLIC...BRUNO
AVIATION...KAPLAN

WWW.WEATHER.GOV/LOSANGELES