Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 311750
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1050 AM PDT FRI JUL 31 2015

.SYNOPSIS...AN UPPER LEVEL TROUGH APPROACHING FROM THE WEST WILL
GRADUALLY PUT AN END TO THE MOIST MONSOONAL FLOW INTO THE WEEKEND.
THERE REMAINS A SLIGHT CHANCE OF THUNDERSTORMS FOR INTERIOR
MOUNTAINS AND DESERTS TODAY...AND LINGERING INTO SATURDAY. COASTAL
CLOUDS ARE EXPECTED BY MORNING THROUGHOUT THE PERIOD WITH NEAR
NORMAL TEMPERATURES.

&&

.SHORT TERM (REST OF TODAY-SUN)...THE 1200 FT DEEP MARINE LAYER IS
ALLOWING COASTAL STRATUS TO STICK AROUND INTO MID MORNING...MAINLY
OVER COASTAL LA COUNTY. THIS IS HELPED BY OUR INCREASING ONSHORE
PRESSURE GRADIENT...LAX-DAG UP 2.2 FROM 24 HR AGO. A COUPLE OF VERY
NOTICEABLE EDDYS ALSO JUST OFFSHORE TO HELP PILE STRATUS INTO THE
COAST. EXPECT STRATUS TO GRADUALLY CLEAR TO THE BEACHES THROUGH THE
MORNING.

DESPITE SOME DRYING FOR TODAY...AS CONFIRMED BY THE GPS-MET
PRECIPITABLE WATER (PW) VAPOR DATA WITH ALL SITES CONTINUING ON THE
DECREASE FROM YESTERDAY`S PEAK OF NEAR 2 INCHES...THERE REMAINS
CHANCES OF SHOWERS AND THUNDERSTORMS FROM THE MOUNTAINS EASTWARD
THIS AFTERNOON...AND AS EVIDENCED BY SOME CU FORMING OVER VTU AND LA
COUNTY MOUNTAINS THIS HOUR. PWS...NOW AROUND 1.5 INCHES AND FALLING
WILL STILL BE ABOVE NORMAL FOR THIS TIME OF YEAR. MODEL FORECAST
SOUNDINGS INDICATE ANOTHER ROUND OF NEGATIVE LIFTED INDICES THIS
AFTERNOON...ALTHOUGH GOES SOUNDER IMAGERY SHOWING ATMOS IS SLOWLY
STABILIZING...BUT THAT TREND SHOULD REVERSE SOON. FINALLY...WE LACK
ANY UPPER LEVEL KICKER TO HELP ENHANCE CONVECTION. CONSIDERING ALL
THESE FACTORS...ACTIVITY WILL BE CONSIDERABLY LESS TODAY COMPARED TO
YESTERDAY. MANY OF THE CONVECTIVE PARAMETERS WILL BECOME LESS
FAVORABLE AS THE AFTERNOON PROGRESSES SO WOULD EXPECT A PRETTY QUICK
DECREASE BY EARLY EVENING OF ANY ACTIVITY THAT DOES DEVELOP.

ADDITIONAL DRYING STILL EXPECTED THROUGH THE WEEKEND FOR EVEN LESSER
CHANCES OF MOUNTAIN AND DESERT TSTORMS. CONTINUED OVERNIGHT COASTAL
STRATUS ALSO LOOKS TO BE A GOOD BET.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (MON-THU)...THE UPPER LOW WELL OFF THE COAST OF PT
CONCEPTION WILL KEEP SWLY FLOW ALOFT ACROSS THE REGION MON THRU THU
AS IT SLOWLY APPROACHES THE COAST. IT IS EXPECTED TO BE DRY THROUGH
THE PERIOD...WITH NO CHANCE OF CONVECTION. NIGHT THRU MORNING LOW
CLOUDS AND FOG WILL LIKELY AFFECT MOST COASTAL AND SOME VLY AREAS
EACH DAY. MAX TEMPS WILL GENERALLY BE NEAR TO SLIGHTLY BELOW NORMAL
THROUGH THE PD.

&&

.AVIATION...31/1800Z...

MID/UPPER LEVEL TROUGH SOUTHWEST OF THE AREA WILL APPROACH. UPPER
LEVEL MODERATE AND DRY SOUTH WINDS WILL BECOME LIGHT SOUTH WHILE MID
LEVEL LIGHT TO MODERATE RELATIVELY DRY SOUTHEAST WINDS BECOME LIGHT
SOUTHEAST AFTER 01/20Z. MODERATE ONSHORE PRESSURE GRADIENT THROUGH
01/04Z AND AFTER 01/20Z OTHERWISE WEAK ONSHORE GRADIENT. ISOLATED
THUNDERSTORMS OVER THE HIGHER TERRAIN BETWEEN 31/20-01/03Z.
THUNDERSTORMS ARE EXPECTED TO MOVE NORTH AROUND 20 KT WITH TOPS
APPROXIMATELY 43KFT. RELATIVELY WEAK CAPPING MARINE INVERSION WITH A
BASE APPROXIMATELY 1.9KFT THE MORNING MAY DIFFER BY MINUS .2KFT.
MARINE CLOUD FIELD WAS ORGANIZED THIS MORNING AND WILL LIKELY BE
ORGANIZED SATURDAY MORNING.

MARINE LAYER AT LAX AT 1500Z IS 1968 FEET DEEP AND THE INVERSION TOP
IS AT 4443 FEET WITH A TEMP OF 22.5 DEGREES C.

KLAX...CHANCE CIGS 015 THROUGH 31/19Z. CHANCE CIGS 010 BETWEEN 01/03-
01/05Z. CHANCE CIGS 007 BETWEEN 01/05-01/12Z AND CIGS 015 BETWEEN
01/12-01/19Z.

KBUR...CHANCE CIGS 015 AFTER 01/10Z

VIRTUALLY CERTAIN - 95-100%
VERY LIKELY       - 80-95%
LIKELY            - 60-80%
CHANCE            - 30-60%
VERY UNLIKELY     - 20% OR LESS

&&

.MARINE...31/900 AM...

SMALL CRAFT ADVISORY CONDITIONS ARE LIKELY FROM POINT CONCEPTION TO
SOUTH OF SAN NICOLAS ISLAND THIS AFTERNOON THROUGH EARLY SATURDAY
MORNING. SMALL CRAFT ADVISORY CONDITION WILL LIKELY CONTINUE FROM
THE NORTHERN CHANNEL ISLANDS TO SOUTH OF SAN NICOLAS ISLAND SATURDAY
AFTERNOON TO SUNDAY NIGHT AND THERE IS A CHANCE SCA CONDITIONS WILL
PERSIST THROUGH TUESDAY.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...MJ/DB
AVIATION/MARINE...30
SYNOPSIS...RM

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