Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 050544
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATE
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1040 PM PDT SAT JUL 4 2015

UPDATED AVIATION DISCUSSION

.SYNOPSIS...
UPPER LEVEL LOW PRESSURE OFF THE COAST WILL MAINTAIN ONSHORE FLOW
THROUGH EARLY NEXT WEEK...BRINGING NIGHT THROUGH MORNING LOW CLOUDS
AND FOG TO THE COASTAL PLAIN. THE UPPER LOW WILL MOVE ACROSS
NORTHERN CALIFORNIA LATER NEXT WEEK...RESULTING IN AN INCREASE IN
MARINE LAYER CLOUD COVERAGE. A GRADUAL COOLING TREND IS EXPECTED
THROUGH NEXT WEEK...WITH SLIGHTLY BELOW NORMAL TEMPERATURES.

&&

.SHORT TERM (TONIGHT-TUE)...EVENING UPDATE

AS EXPECTED...TODAY`S HIGHS ACROSS THE VALLEYS TRENDED COOLER 5 TO
10 DEGREES IN MOST AREAS...WHILE THE COASTAL AREAS WERE ABOUT THE
SAME OR A DEGREE OR TWO COOLER TODAY. THE ONE AREA THAT WARMED UP
FROM YESTERDAY WAS THE ANTELOPE VALLEY...LIKELY FROM DOWNSLOPING
WINDS OVER THE SAN GABRIEL MTNS. LATEST VIS SAT IMAGERY INDICATED
LOW CLOUDS ALREADY PUSHING IN ACROSS MANY IMMEDIATE COASTAL AREAS
THIS EVENING. EXPECT THE LOW CLOUDS TO SURGE INLAND LATER THIS
EVENING. LATEST AMDAR SOUNDING NEAR LAX INDICATED THE MARINE LAYER
AROUND 1600 FT DEEP ALREADY. THIS SHOULD BE GOOD NEWS FOR PEOPLE
WATCHING FIREWORKS ALONG THE LOS ANGELES COUNTY COAST AS THE BASE OF
THE CLOUDS WERE AROUND 1200 FT DEEP. CURRENTLY OXNARD AIRPORT WAS
SHOWING A BASE OF 700 FT...BUT WOULD NOT BE SURPRISED IF IT RAISED A
FEW HUNDRED BY 9 PM THIS EVENING. NEVERTHELESS...EXPECT LOW CLOUDS
ACROSS MOST COASTAL AREAS THIS EVENING..SPREADING INLAND OVERNIGHT
INTO MOST COASTAL VALLEYS. PEOPLE WATCHING FIREWORKS ACROSS THE
CENTRAL COAST...I.E. PISMO BEACH OR CUYACOS WILL ALSO DEAL WITH LOW
CLOUDS...WITH CLOUD BASES A BIT LOWER.

SYNOPTICALLY...THIS IS MUCH MORE OF A JUNE GLOOM PATTERN THAN THE
EARLIER HUMID MONSOON PATTERN WE WERE STUCK IN FOR MOST OF THE PAST
WEEK. A REX BLOCK PATTERN OFF THE COAST WITH AN EXPANSIVE UPPER LOW
OFF THE CALIFORNIA COAST...AND A STRONG 590 DM HIGH JUST OFF THE
CANADIAN WEST COAST. THE UPPER LOW WILL MOVE CLOSER TO NORTHERN
CALIFORNIA OVER THE NEXT TWO DAYS ALLOWING FOR THE UPPER TROUGH TO
LINGER OVER THE REGION. EXPECT THE COOLING TREND TO CONTINUE ONCE
AGAIN TOMORROW AND MONDAY A FEW DEGREES WITH LITTLE CHANGE FOR
TUESDAY. THERE WILL CONTINUE TO BE NIGHT THROUGH MORNING LOW CLOUDS
AND PATCHY FOG IN SOME VALLEY LOCATIONS. THERE SHOULD BE A FEW
DEGREES OF COOLING ACROSS THE ANTELOPE VALLEY TOMORROW AS HEIGHTS
SHOULD CONTINUE TO LOWER A BIT. STRONG ONSHORE GRADIENTS WILL
CONTINUE THROUGH TUE ALLOWING FOR GUSTY SW WINDS ACROSS PORTIONS OF
THE LA COUNTY MTNS INTO THE ANTELOPE VALLEY AND ADJACENT FOOTHILLS
EACH AFTERNOON. THERE COULD BE A FEW GUSTS TO 45 MPH AROUND LAKE
PALMDALE. THERE WILL BE SOME CUMULUS BUILDUPS OVER THE VENTURA
COUNTY MTNS SUNDAY AFTERNOON AND EVENING AS INSTABILITY PARAMETERS
PUT A BULLSEYE OVER THAT AREA. ALTHOUGH THERE WILL BE RELATIVELY
HIGH CAPE...LIFTED INDEX AROUND -7 AND K INDEX AROUND 40...THERE
WILL BE A THIN POOL OF MOISTURE AROUND 700 MB TO WORK WITH. NOT
ENOUGH TO INITIATE ELEVATED THUNDERSTORMS TOMORROW AFTERNOON.

***FROM PREVIOUS DISCUSSION***

.LONG TERM (WED-SAT)...THE UPPER LOW WILL SHIFT SLOWLY EASTWARD ON
WEDNESDAY...PUSHING ONSHORE OVER THE BAY AREA THURSDAY AND THEN
LIFTING TO THE NORTHEAST MORE RAPIDLY FRIDAY INTO SATURDAY. THE MAIN
EFFECT OVER SOUTHWEST CALIFORNIA WILL BE TO FURTHER DEEPEN THE
MARINE LAYER SO THAT IT WILL EXTEND OVER THE INLAND VALLEYS AND THE
LOWER COASTAL MOUNTAIN SLOPES. SOME DRIZZLE MAY ALSO BE POSSIBLE AS
THIS OCCURS. A SLOW COOLING TREND WILL ALSO OCCUR THROUGH FRIDAY.

&&

.AVIATION...05/0540Z...

AT 0507Z...THE MARINE INVERSION AT KLAX WAS BASED AT 1400 FEET. THE
TOP OF THE INVERSION WAS 5000 FEET WITH A TEMPERATURE OF 23 DEGREES
CELSIUS.

EXPECT WIDESPREAD STRATUS WITH LIFR TO IFR CONDS IN COASTAL AREAS
SPREADING INTO THE VLYS LATE TONIGHT. CONDS MAY IMPROVE TO MVFR
ACROSS CSTL SXNS OF L.A. COUNTY SUN MORNING BEFORE CIGS SCATTER OUT.
EXPECT SLOW CLEARING NEAR THE COAST SUN...AND SOME LOCATIONS NEAR
THE BEACHED MAY NOT CLEAR AT ALL SUNDAY.

KLAX...MODERATE CONFIDENCE IN THE 06Z TAF. THERE IS A 30% CHANCE
THAT CIGS WILL NOT SCATTER OUT SUNDAY AFTERNOON.

KBUR...MODERATE CONFIDENCE IN THE 06Z TAF. THERE IS A 20 TO 30%
PERCENT CHANCE THAT CIGS WILL ARRIVE AS EARLY AS 09Z.

&&

.MARINE...04/900 PM...

FOR THE OUTER WATERS...HIGH CONFIDENCE IN WEST TO NORTHWEST WINDS
REMAINING BELOW SMALL CRAFT ADVISORY LEVELS THROUGH SUNDAY NIGHT
(ALTHOUGH THERE MAY BE SOME LOCAL GUSTS TO 25 KT IN THE AFTERNOON
AND EVENING HOURS). FOR MONDAY THROUGH WEDNESDAY...THE WINDS WILL
INCREASE A BIT...AND THERE IS A GOOD CHANCE OF SMALL CRAFT ADVISORY
CONDITIONS DEVELOPING.

FOR THE INNER WATERS...HIGH CONFIDENCE IN WESTERLY WINDS REMAINING
BELOW SMALL CRAFT ADVISORY LEVELS THROUGH SUNDAY. FROM MONDAY
THROUGH WEDNESDAY...THE WINDS WILL INCREASE A BIT. THERE IS A SLIGHT
CHANCE OF SMALL CRAFT ADVISORY LEVEL GUSTS ACROSS WESTERN SECTIONS
EACH AFTERNOON AND EVENING.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
NONE

&&

$$

PUBLIC...KAPLAN/SMITH
AVIATION/MARINE...CK/RAT
SYNOPSIS...SUKUP

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