Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 301252 AAA
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
515 AM PDT THU JUL 30 2015

UPDATED AVIATION SECTION

.SYNOPSIS...MONSOONAL MOISTURE WILL BRING INCREASED HUMIDITY AND A
CHANCE OF SHOWERS AND THUNDERSTORMS TO THE REGION TODAY AND TONIGHT.
THE CHANCE OF THUNDERSTORMS WILL CONTINUE ACROSS THE MOUNTAINS...
DESERTS AND INTERIOR VALLEYS INTO THE WEEKEND...MAINLY DURING THE
AFTERNOON AND EVENING HOURS. SOUTHWESTERLY FLOW ALOFT WILL RETURN
MONDAY AND PERSIST THROUGH MID WEEK...BRINGING DRY WEATHER WITH NEAR
NORMAL TEMPERATURES.

&&

.SHORT TERM (TODAY-SAT)...EXCEPT FOR SOME PATCHY LOW CLOUDS AND FOG
ON THE CENTRAL COAST AND ACROSS THE S COAST OF SBA COUNTY...SKIES
WERE MOSTLY CLEAR ACROSS THE REGION EARLY THIS MORNING. MID LEVEL
CLOUDS AND SOME SHOWERS/ISOLATED TSTMS ATTRIBUTABLE TO AN EASTERLY
WAVE AND ASSOCD VORT WERE MOVING WESTWARD THROUGH THE SRN DESERTS
TOWARD THE FORECAST AREA. SKIES SHOULD BECOME PARTLY CLOUDY FROM SE
TO NW ACROSS THE REGION TODAY...AND AT TIMES IT WILL LIKELY BE
MOSTLY CLOUDY. LIFTING ASSOCD WITH THE APPROACHING VORT...AND
INCREASING INSTABILITY WITH DAYTIME HEATING AND SLIGHT COOLING
ALOFT SHOULD CAUSE SHOWER AND TSTM ACTIVITY TO DEVELOP LATER THIS
MORNING ACROSS L.A. COUNTY...WITH THE CHANCE OF SHOWERS/STORMS
EXPANDING NWWD...REACHING SLO COUNTY THIS AFTERNOON.

WHILE THE BULK OF THE SHOWER AND THUNDERSTORM ACTIVITY IS LIKELY TO
BE IN THE MTNS AND ANTELOPE VALLEY...THERE WILL BE AT LEAST A SLIGHT
CHANCE OF SOME SHOWERS/STORMS DRIFTING WWD INTO COASTAL AND VALLEY
AREAS DUE TO THE EAST TO SOUTHEAST STEERING FLOW. PRECIPITABLE WATER
VALUE ARE FORECAST TO JUMP TO ABOUT 2.1 INCHES...INDICATIVE OF A
VERY MOISTURE RICH ENVIRONMENT. ANY THUNDERSTORM WILL HAVE THE
POTENTIAL TO PRODUCE HEAVY TO INTENSE RAINFALL. WHILE THE STEERING
FLOW LOOKS TO BE STRONG ENOUGH TO KEEP STORMS MOVING MORE QUICKLY
THAN THOSE THAT WOULD NORMALLY PRODUCE FLASH FLOODING...THE AMOUNT
OF AVAILABLE MOISTURE IN THE ATMOSPHERE AND THE POTENTIAL FOR STORMS
TO TRAIN OVER ANY LOCATION WILL RAISE THE SPECTER OF FLASH FLOODING.
THIS WILL BE MOST LIKELY IN HIGHER ELEVATIONS WHERE THERE WILL BE
LESS OPPORTUNITY FOR RAIN TO EVAPORATE AS IT MOVES THROUGH THE DRIER
LOW LAYERS. THEREFORE...FLASH FLOOD WATCHES HAVE BEEN ISSUED FOR THE
ANTELOPE VALLEY...THE CUYAMA VALLEY...AND THE MOUNTAINS OF SBA...VTU
AND L.A. COUNTIES (EXCLUDING THE SANTA MONICAS). HAVE ALSO EXPANDED
THE FLASH FLOOD WATCH TO INCLUDE THE COLBY BURN AREA IN THE
FOOTHILLS ABOVE THE SAN GABRIEL VALLEY. HEAVY RAINFALL ON ANY BURN
AREA COULD BRING MUD AND DEBRIS FLOWS...BUT IT IS MOST LIKELY IN THE
HIGHER TERRAIN OF LOS ANGELES COUNTY.

MAX TEMPS WILL BE TRICKY TODAY...DUE TO THE OPPOSING FACTORS OF
INCREASED CLOUD COVER AND WEAKER ONSHORE PRES GRADIENTS THAT MAY
EVEN FLIP SLIGHTLY OFFSHORE. AT THIS POINT...BELIEVE THERE WILL BE
SOME WARMING TODAY...UNLESS IT IS CLOUDIER THAN EXPECTED. WHERE
THERE IS ENOUGH SUNSHINE...MAX TEMPS MAY WELL BE SEVERAL DEGREES
HIGHER THAN THEY WERE ON WED. ALTHOUGH TEMPS WILL NOT NECESSARILY BE
MUCH...IF AT ALL...ABOVE NORMAL...THE INCREASED HUMIDITY WILL MAKE
FOR MORE DISCOMFORT FOR MOST PEOPLE.

THE THREAT OF SHOWERS/TSTMS WILL END IN MOST COASTAL AND VALLEY
AREAS THIS EVENING...BUT A SLIGHT CHANCE WILL PERSIST IN THE MTNS
AND DESERTS...AND INTERIOR SECTIONS OF SLO AND SBA COUNTIES
OVERNIGHT AND FRI MORNING. WITH DAYTIME HEATING...THE CHANCE OF
SHWRS/TSTMS WILL INCREASE IN THE MTNS AND DESERTS FRI AFTERNOON AND
EVENING. WHILE THE ATMOSPHERE WILL NOT BE QUITE AS MOISTURE RICH AS
IT IS TODAY...HEAVY DOWNPOURS ARE STILL POSSIBLE. AT THIS TIME...DO
NOT EXPECT MUCH SHOWER ACTIVITY W OF THE MTNS ON FRI. MAX TEMPS
SHOULD BE ABOUT THE SAME AS THOSE OF TODAY IN MOST AREAS...POSSIBLY
A BIT COOLER AS ONSHORE GRADS INCREASE.

THE CHANCE OF SHOWERS/TSTMS WILL BE A BIT LOWER SAT...AND LIKELY
CONFINED TO THE MTNS AND DESERTS DURING THE AFTERNOON AND EVENING
HOURS. MAX TEMPS SHOULD NOT CHANGE TOO MUCH ON SAT.

.LONG TERM (SUN-WED)...A BROAD TROUGH MOVING INTO THE ERN PACIFIC
WILL CAUSE DRIER SWLY FLOW ALOFT TO GRADUALLY PUSH INTO THE REGION
SUN...BUT THERE STILL MAY BE SOME AFTERNOON AND EVENING
SHOWERS/TSTMS OVER THE L.A. COUNTY MTNS AND DESERTS. DRY WEATHER IS
EXPECTED MON THROUGH WED. MAX TEMPS SHOULD GENERALLY BE CLOSE TO
NORMAL FOR EARLY AUGUST IN MOST AREAS.

&&

.AVIATION...30/1100Z...

AT 0835Z...THE MARINE INVERSION AT KLAX WAS BASED AT 700 FEET. THE
TOP OF THE INVERSION WAS 3600 FEET WITH A TEMPERATURE OF 26 DEGREES
CELSIUS.

OVERALL...MODERATE CONFIDENCE IN 12Z TAF PACKAGE. IFR/LIFR CIG
RESTRICTIONS LIMITED TO KSMX/KSBP AND KSBA THIS MORNING...AND SHOULD
DISSIPATE AROUND 17Z. OTHERWISE...VFR CONDS ANTICIPATED AT ALL SITES
THRU THE PERIOD. MAIN CONCERN WILL BE THE POSSIBILITY OF
THUNDERSTORMS AS A DISTURBANCE MOVES ACROSS THE AREA. BEST CHANCES
FOR THUNDERSTORMS WILL BE AT KPMD/KWJF AND WILL INCLUDE VCTS REMARKS
FOR THOSE SITES. ELSEWHERE...THERE IS A SLIGHT CHANCE OF
THUNDERSTORMS LATER THIS MORNING THROUGH THIS EVENING...BUT ANY
ACTIVITY WILL LIKELY BE ISOLATED...PRECLUDING ANY MENTION IN COASTAL
OR VALLEY TAF SITES.

KLAX...MODERATE CONFIDENCE IN 12Z TAF. THERE IS A 20% CHANCE OF
IFR/MVFR CIG RESTRICTIONS 12Z-18Z. OTHERWISE...VFR CONDS WILL
PREVAIL WITH A SLIGHT CHANCE (15%) OF A THUNDERSTORM AT THE AIRFIELD.

KBUR...HIGH CONFIDENCE IN 12Z TAF. VFR CONDS SHOULD PREVAIL THRU THE
PERIOD WITH A SLIGHT CHANCE (15-20%) OF A THUNDERSTORM AT THE
AIRFIELD.

&&

.MARINE...30/300 AM...

FOR THE OUTER WATERS...MODERATE TO HIGH CONFIDENCE IN WINDS
REMAINING BELOW SCA LEVELS THROUGH FRIDAY NIGHT. ON SATURDAY AND
CONTINUING THROUGH MONDAY...NORTHWEST WINDS WILL INCREASE AND THERE
IS A GOOD CHANCE OF SCA CONDITIONS DEVELOPING...ESPECIALLY IN THE
AFTERNOON AND EVENING HOURS.

FOR THE INNER WATERS...HIGH CONFIDENCE IN WINDS REMAINING BELOW SCA
LEVELS THROUGH MONDAY...ALTHOUGH THERE IS A SLIGHT CHANCE OF GUSTS
REACHING SCA LEVELS ACROSS WESTERN SECTIONS DURING THE AFTERNOON AND
EVENING HOURS SATURDAY THROUGH MONDAY.

A MOIST AND UNSTABLE AIR MASS WILL BRING THE THREAT OF THUNDERSTORMS
TO THE COASTAL THIS MORNING THROUGH THIS EVENING. ANY THUNDERSTORMS
THAT DEVELOP WILL BE CAPABLE OF PRODUCING HEAVY RAIN...CLOUD TO
SURFACE LIGHTNING AND EVEN A WATERSPOUT.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
FLOOD WATCH (SEE LAXFFALOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
SPECIAL WEATHER STATEMENT (SEE LAXSPSLOX).

&&

$$

PUBLIC...DB
AVIATION/MARINE...RAT

WWW.WEATHER.GOV/LOSANGELES


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