Area Forecast Discussion
Issued by NWS Los Angeles, CA

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS66 KLOX 301758
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1055 AM PDT THU JUL 30 2015

UPDATED AVIATION DISCUSSION

.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...30/1755Z...

MARINE LAYER AROUND 010 THIS MORNING.

ALL AIRPORTS IN VFR THIS MORNING. MODERATELY CONFIDENT THAT SHOWERS
AND THUNDERSTORM CHANCES WILL DECREASE OVER THE COASTAL AND VALLEY
LOCATIONS THIS AFTERNOON.  KWJF KPMD AND KPRB HAVE A 20-30 PERCENT
CHANCE OF A THUNDERSTORM THIS AFTERNOON AND EVENING...POSSIBLY
LINGERING THROUGH MOST OF FRIDAY. STRATUS WILL BE GREATLY RESTRICTED
DUE TO NEARBY CONVECTION...BUT EXPECTING A FEW RANDOM PATCHES TO BE
AROUND SOME COASTAL AIRPORTS TONIGHT INTO FRIDAY MORNING. WEAKER
THAN USUAL WINDS WILL PREVAIL TODAY...EXCEPT FOR POSSIBLE GUSTY
WINDS NEAR ANY THUNDERSTORMS.

KLAX...MODERATE CONFIDENCE IN VFR THROUGH FRIDAY...WITH A 30 PERCENT
CHANCE OF IFR CIGS FORMING BECOMING 03 AND 17Z. MAIN THREAT OF
CONVECTION HAS SHIFTED WELL INLAND...BUT THERE STILL IS A 10 PERCENT
CHANCE OF A TSRM INTO THIS EVENING.

KBUR...HIGH CONFIDENCE IN VFR THROUGH FRIDAY. MAIN THREAT OF
CONVECTION HAS SHIFTED WELL INLAND...BUT THERE STILL IS A 10 PERCENT
CHANCE OF A TSRM INTO THIS EVENING.

&&

.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/MARINE...KITTELL
SYNOPSIS...MUNROE

WWW.WEATHER.GOV/LOSANGELES



USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.