Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 301619 AAA
AFDLOX

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

.SYNOPSIS...

THERE IS A CHANCE OF THUNDERSTORMS TODAY FOR THE INTERIOR MOUNTAINS
AND DESERTS WITH A SLIGHT CHANCE ELSEWHERE. THE THUNDERSTORM THREAT
WILL BECOME CONFINED TO THE INTERIOR MOUNTAINS AND DESERTS THROUGH
SATURDAY. BY MONDAY STABILIZING SOUTHWEST FLOW ALOFT WILL END THE
THREAT OF THUNDERSTORMS WITH A RETURN TO SEASONAL TEMPERATURES.

&&

.SHORT TERM (TODAY-SAT)...

FORECAST FOR TODAY LOOKS TO BE IN GOOD SHAPE SO NO MAJOR CHANGES
WERE MADE WITH THE MORNING UPDATE. JUST TWEAKED THE SKY GRID BASED
ON CURRENT SATELLITE IMAGERY. THE NAM SEEMS TO BE DOING A GOOD JOB
WITH THE LITTLE MID-LEVEL INVERTED TROUGH THAT IS MOVING THROUGH THE
AREA. SCATTERED TO ISOLATED SHOWERS MOVING ACROSS LA AND VENTURA
COUNTY THIS MORNING MATCH UP WELL WITH THE NAM INITIALIZATION OF
THIS FEATURE. THE NAM SHOWS THE DISTURBANCE EXITING SLO COUNTY BY
THIS EVENING...WHICH MATCHES UP WELL WITH THE SLIGHT CHANCE TO
CHANCE THREAT OF SHOWERS AND THUNDERSTORMS SPREADING NORTHWARD
TODAY. WILL RE-EVALUATE THE THUNDERSTORM CHANCES FOR THE COASTAL AND
VALLEY AREAS FOR THIS EVENING WITH THE AFTERNOON UPDATE. THE THREAT
SHOULD DECREASE LATER THIS AFTERNOON AND THIS EVENING AFTER THE
SHORT-WAVE MOVES THROUGH...BUT WILL WAIT TO SEE HOW THINGS GO THIS
AFTERNOON.

***FROM PREVIOUS DISCUSSION***

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...29/900 AM.

UNSTABLE AIR IS PUSHING FROM SOUTH TO NORTH TODAY WITH A 20 PERCENT
CHANCE OF A THUNDERSTORM FORMING OVER THE COASTAL WATERS. MODERATE
TO HIGH CONFIDENCE OF NO THUNDERSTORMS EXPECTED AFTER THIS EVENING.
30 PERCENT CHANGE OF LOW GRADE SMALL CRAFT ADVISORY WINDS SOUTH OF
POINT CONCEPTION TONIGHT AND FRIDAY NIGHT. SMALL CRAFT ADVISORY
WINDS LIKELY OVER THE WEEKEND OVER THE OUTER WATERS...WITH CHOPPY
CONDITIONS OVER THE INNER WATERS.

&&

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

&&

$$

PUBLIC...SUKUP/DB
AVIATION...RAT
MARINE...KITTELL
SYNOPSIS...MUNROE

WWW.WEATHER.GOV/LOSANGELES


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