Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 131709 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1010 AM PDT SUN JUL 13 2014

...UPDATED AVIATION AND MARINE DISCUSSIONS...

.SYNOPSIS...
A WARMING TREND WILL CONTINUE TODAY AS HIGH PRESSURE CONTINUES TO
BUILD...WITH TRIPLE DIGIT HEAT EXPECTED FOR THE DESERT AND HOTTEST
VALLEY LOCATIONS THROUGH MONDAY. SOME MONSOONAL MOISTURE WILL ARRIVE
TODAY...BRINGING A SLIGHT CHANCE TO CHANCE OF MOUNTAINS AND DESERT
THUNDERSTORMS THROUGH MUCH OF NEXT WEEK.

&&

.SHORT TERM (TODAY-TUE)...
ISSUED AN UPDATE TO CHANGE TODAYS SKY WORDING TO MOSTLY SUNNY XCP
FOR THE LA/VTA MTNS WHICH WILL TURN PARTLY CLOUDY WITH AFTERNOON
CONVECTION. OTHERWISE CURRENT FCST ON TRACK WITH WARMEST TEMPS TODAY
AND CONVECTION BOTH DURING THE AFTERNOON AND OVERNIGHT. THE VORT MAX
IS STILL SLATED TO MOVE THROUGH AREA EARLY TOMORROW...BRING A SLGT
CHC OF TSTMS ALL THE WAY TO THE CENTRAL COAST (THE LA AND VTA CSTS
AND VLYS SHOULD STAY DRY) THE INCREASE IN HUMIDITIES WILL MAKE
EVERYTHING THAT MUCH MORE UNCOMFORTABLE.

...FROM THE PREVIOUS DISCUSSION...

A STRONG UPPER LEVEL HIGH PRESSURE SYSTEM CURRENTLY CENTERED OVER
NEVADA WILL BRING A RETURN OF MONSOONAL MOISTURE FROM NORTHERN
MEXICO AND ARIZONA TO SOUTHWEST CALIFORNIA DURING THE NEXT FEW DAYS.
THERE WILL BE A SIGNIFICANT INCREASE IN TEMPERATURES TODAY ACROSS
INLAND AREAS...WITH WARMEST INTERIOR LOCATIONS REACHING TRIPLE
DIGITS. THIS DUE TO A COMBINATION OF INCREASING HEIGHTS AND
THICKNESS LVLS AS WELL AS WEAK SURFACE OFFSHORE FLOW EXPECTED
THROUGH THIS AFTERNOON. THE WARMEST LOCATIONS ARE EXPECTED TO BE THE
LOWER MOUNTAIN ELEVATIONS...ANTELOPE VALLEY AND THE INTERIOR VALLEYS
OF SLO COUNTY...WHICH WILL LIKELY SEE HIGHS BETWEEN 105 AND 108
DEGREES. THE INFLUX OF MONSOONAL MOISTURE INTO LOS ANGELES AND
VENTURA COUNTIES TODAY WILL ADD TO THE DISCOMFORT. WARMEST MOUNTAIN
LOCATIONS WILL LIKELY HAVE HEAT INDEX VALUES LOCALLY REACHING
CRITICAL HEAT WARNING THRESHOLDS OF 100 DEGREES THIS AFTERNOON. FOR
MONDAY...HIGH TEMPS WILL BE A FEW DEGREES COOLER INLAND...MAINLY DUE
TO THE ADDED HUMIDITY IN THE ATMOSPHERE. NEVERTHELESS...IT WILL
CONTINUE TO REMAIN QUITE HOT ACROSS THE FORECAST AREA...AND WITH THE
ADDED HUMIDITY IT WILL CONTINUE TO FEEL VERY MUGGY ACROSS THE
INTERIOR AREAS BOTH MONDAY AND TUESDAY.

AS FAR AS CONVECTION OVER THE NEXT FEW DAYS...THERE WILL BE A SLIGHT
CHANCE FOR A FEW ISOLATED ELEVATED THUNDERSTORMS ACROSS THE EASTERN
SAN GABRIEL MOUNTAINS AND ADJACENT EASTERN PORTION OF THE ANTELOPE
VALLEY...AS WELL AS THE VENTURA COUNTY MOUNTAINS THIS AFTERNOON AND
EARLY EVENING HOURS. IF STORMS DO DEVELOP TODAY...THE MAIN IMPACT
WILL BE DRY LIGHTNING AND GUSTY OUTFLOW WINDS DUE TO COLLAPSING
STORMS. PRECIPITABLE WATER (PWAT) WILL WILL REMAIN UNDER 1.5 INCHES
TODAY AND UPPER STEERING WINDS FROM THE EAST WILL BE RELATIVELY
STRONG...SO NOT ANTICIPATING ANY FLASH FLOODING TODAY IN THE
MOUNTAINS AND ANTELOPE VALLEY TODAY. BOTH THE NAM-WRF AND GFS WERE
INDICATING A VORT MAX MOVING OVER LA COUNTY INTERIOR AREAS LATE
TONIGHT INTO MONDAY MORNING. CROSS SECTIONS SHOWED SOME LIFT
ASSOCIATED WITH THIS VORT MAX WHICH COULD KICK OFF A FEW SHOWERS OR
ELEVATED THUNDERSTORMS EARLY MONDAY MORNING. HAVE KEPT SLIGHT POPS
IN THE FORECAST FOR MONDAY MORNING FROM THE LA/VTU COUNTY MTNS TO
THE CENTRAL COAST. BY MONDAY AFTERNOON...THE ATMOSPHERE SHOULD BE
MOISTENING UP AS THE PWAT VALUES WILL INCREASE TO AROUND 1.75".
INSTABILITY LOOKS TO BE MARGINAL...BUT STORMS SHOULD INITIATE OVER
SAN BERNARDINO COUNTY THEN BUILD TO THE WEST INTO LA AND VENTURA
COUNTY MTNS AND ANTELOPE VALLEY. THERE WILL BE A BETTER CHANCE
FOR LOCAL FLASH FLOODING DUE TO MORE MID LEVEL MOISTURE TO WORK
WITH. STEERING FLOW OUT OF THE EAST TO SOUTHEAST WILL CONTINUE TO BE
STRONG BUT IF STORMS BACK BUILD OR START TO "TRAIN"..EXPECT LOCAL
FLASH FLOODING ACROSS SOME MOUNTAIN ROADS AND ARROYOS THAT CROSS A
FEW MAIN ROADS IN THE ANTELOPE VALLEY...SUCH AS HIGHWAY 138 AND
PALMDALE ROAD.

FOR TUESDAY...THE UPPER LEVEL PATTERN WILL SHIFT MORE OUT OF THE
SOUTHEAST WHICH WILL CONTINUE TO USHER IN MONSOONAL MOISTURE. THERE
WILL BE ANOTHER ROUND OF THUNDERSTORM ACTIVITY ONCE AGAIN...AND
POSSIBLY FURTHER NORTHWEST INTO SANTA BARBARA COUNTY MTNS AND
INTERIOR VALLEYS. UPPER STEERING WINDS WILL BECOME WEAKER WHICH
SHOULD INCREASE THE FLASH FLOODING THREAT TUE AFTERNOON THROUGH
EVENING FOR SAME AREAS.

.LONG TERM (WED-SAT)...A MID LEVEL DRYING TREND IS EXPECTED BY WED.
HOWEVER...850 MB DEWPOINTS OVER 10 DEGREES C REMAIN IN PLACE ACROSS
LA/VTU COUNTIES THROUGH THURSDAY. THEREFORE SLIGHT CHANCE POPS WILL
REMAIN IN THE FORECAST FOR THE LA/VTU COUNTY MTNS AND ANTELOPE
VALLEY THROUGH THURSDAY. HIGH TEMPS WILL CHANGE LITTLE OVER THE
EXTENDED PERIOD BUT SHOULD BE A TAD COOLER COMPARED TO MON/TUE.
ONSHORE FLOW WILL STRENGTHEN A BIT WHICH WILL HELP THE MARINE LAYER
STRATUS BECOME MORE ORGANIZED FOR NIGHT THROUGH MORNING LOW CLOUDS
AND FOG THROUGH SATURDAY. EXPECT LOW CLOUDS TO BE LIMITED TO THE
COASTAL AREAS THROUGH THU...THEN CREEP INTO THE COASTAL VALLEYS LATE
NEXT WEEK.

&&

.AVIATION...13/1710Z...

OVERALL...MODERATE CONFIDENCE IN 18Z TAF PACKAGE. LATEST SOUNDING
DATA INDICATES MARINE INVERSION BETWEEN 700 AND 1000 FEET. STRATUS
IS DISSIPATING ALONG THE CENTRAL COAST...AND VFR CONDS EXPECTED FOR
ALL SITES THROUGH EARLY THIS EVENING. FOR TONIGHT...EXPECT SOME
IFR/LIFR CONDS TO RETURN TO THE CENTRAL COAST (MAINLY KSMX). ALSO
THERE IS THE POSSIBILITY OF SOME IFR CONDS RETURNING TO KLAX AND
KLGB LATE TONIGHT (ALBEIT WITH LOW CONFIDENCE).

KLAX...OVERALL LOW CONFIDENCE IN 18Z TAF. HIGH CONFIDENCE IN VFR
CONDS THRU THIS EVENING. FOR TONIGHT...LOW CONFIDENCE IN FORECAST
RETURN OF IFR CIGS TO THE AIRFIELD.

KBUR...HIGH CONFIDENCE IN 18Z TAF.

&&

.MARINE...13/1010 AM...

HIGH CONFIDENCE IN SMALL CRAFT ADVISORY CONDITIONS FOR THE OUTER
WATERS (PZZ670/673/676) THROUGH LATE TONIGHT. LOCAL GALE FORCE GUSTS
WILL BE POSSIBLE AROUND POINT CONCEPTION THIS EVENING. WINDS IN THE
INNER WATERS WILL BECOME ELEVATED AND GUSTY IN THE WESTERN PORTIONS
THIS AFTERNOON AND EVENING BUT ARE EXPECTED TO REMAIN BELOW SMALL
CRAFT ADVISORY CRITERIA.

PATCHY DENSE FOG IS POSSIBLE ACROSS THE COASTAL WATERS TONIGHT AND
MONDAY MORNING...ESPECIALLY NORTH OF POINT CONCEPTION.

&&

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

&&
$$

PUBLIC...KAPLAN/ASR
AVIATION...RAT
MARINE...RAT
SYNOPSIS...SUKUP

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