Area Forecast Discussion
Issued by NWS Los Angeles, CA

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000
FXUS66 KLOX 181255
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
534 AM PDT FRI APR 18 2014

...UPDATED AVIATION DISCUSSION...

.SYNOPSIS...
AN UPPER LOW WILL BRING A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS
TO THE MOUNTAINS AND DESERTS THIS AFTERNOON AND EVENING...WITH
PLENTY OF CLOUDS AND A FEW SPRINKLES POSSIBLE ELSEWHERE. AN UPPER
RIDGE WILL BRING WARMING OVER THE WEEKEND...WITH TEMPERATURES ABOVE
NORMAL BY SUNDAY. THERE WILL BE SLIGHT COOLING ON MONDAY...THEN MORE
SIGNIFICANT COOLING ON TUESDAY AS A TROUGH MOVES INTO THE WEST
COAST. SOME WARMING IS POSSIBLE BY THURSDAY.

&&

.SHORT TERM (TODAY-SUN)...SKIES WERE GENERALLY CLOUDY ACROSS THE
REGION THIS MORNING...A MIXTURE OF LOW CLOUDS WITH A DEEP MARINE
LAYER OF AROUND 3000 FEET...AND LOTS OF MID AND HIGH CLOUDS
ASSOCIATED WITH AN UPPER LOW TO THE SW OF THE REGION. THIS UPPER LOW
WILL TRACK JUST TO THE SOUTH OF THE REGION TODAY. MODELS SHOW A FAIR
AMOUNT OF MOISTURE LINGERING ACROSS THE FORECAST AREA...SO EXPECT A
MOSTLY CLOUDY DAY...WITH SOME BREAKS OF SUNSHINE FROM TIME TO TIME.
THE WRF SHOWS SOME MODEST INSTABILITY LATE THIS MORNING THROUGH THIS
EVENING ACROSS THE MTNS OF ERN SBA...VTU AND LOS ANGELES COUNTIES
AND THE ANTELOPE VALLEY. WITH SOME MOISTURE AVAILABLE BETWEEN 500
AND 700 MB...THERE COULD BE SOME ELEVATED CONVECTION TODAY IN THESE
AREAS...ESPECIALLY ACROSS THE MTNS OF VTU COUNTY...WHERE THE BEST
MOISTURE AND INSTABILITY WILL BE FOCUSED. HAVE SLIGHT CHANCE POPS
FOR THOSE AREAS THIS AFTERNOON AND EVENING. THERE COULD EVEN BE A
FEW SPRINKLES IN COASTAL AND VALLEY AREAS OF L.A. AND VTU COUNTIES
TODAY. MAX TEMPS WILL BE NEAR OR SLIGHTLY BELOW THOSE RECORDED ON
THU...GENERALLY A COUPLE OF DEGREES BELOW NORMAL IN MOST AREAS.

THE UPPER LOW WILL MOVE EAST OF THE REGION TONIGHT AND SAT...AND
HEIGHTS AND THICKNESSES ACROSS THE REGION WILL RISE. THERE WILL
LIKELY BE AREAS OF LOW CLOUDS IN MOST COASTAL AND VALLEY AREAS
OVERNIGHT/SAT MORNING...BUT THERE SHOULD BE MORE IN THE WAY OF
SUNSHINE SATURDAY AFTERNOON. THERE COULD BE JUST ENOUGH LINGERING
MOISTURE AND INSTABILITY FOR A FEW BUILDUPS IN THE MTNS OF L.A. AND
VTU COUNTIES SAT AFTERNOON...AND AN ISOLATED THUNDERSTORM WOULD NOT
BE OUT OF THE QUESTION. MAX TEMPS SHOULD BE UP A FEW DEGREES IN MOST
AREAS ON SAT.

N-S GRADIENTS MAY BECOME STRONG ENOUGH TO PRODUCE SOME GUSTY WINDS
THROUGH AND BELOW PASSES AND CANYONS OF THE SANTA YNEZ RANGE AND THE
I-5 CORRIDOR SAT NIGHT...BUT EXPECT WINDS TO REMAIN WELL BELOW
ADVISORY LEVELS. AN UPPER RIDGE WILL AMPLIFY ACROSS REGION ON
SUNDAY. HEIGHTS AND THICKNESSES WILL RISE...AND THERE WILL BE
SIGNIFICANT WARMING AT 850 AND 950 MB. THE MARINE INVERSION WILL
LOWER...WITH NIGHT THROUGH MORNING STRATUS LIKELY CONFINED TO THE
COASTAL PLAIN. EXPECT MAX TEMPS TO JUMP UP SEVERAL DEGREES ON
SUNDAY...ESPECIALLY AWAY FROM THE COASTAL PLAIN...WITH HIGHS IN THE
80S EXPECTED IN THE VALLEYS.

.LONG TERM (MON-THU)...THE UPPER RIDGE WILL FLATTEN AND BE FORCED
EASTWARD ON MONDAY AS A TROUGH APPROACHES THE WEST COAST. THE MARINE
LAYER MAY DEEPEN A BIT...AND SOME LOW CLOUDS COULD PUSH INTO  LOWER
VALLEY LOCATIONS. EXPECT SOME COOLING...ESPECIALLY WEST OF THE
MOUNTAINS...WITH MINOR CHANGES IN MAX TEMPS IN THE MTNS AND DESERTS.
THE UPPER TROUGH WILL MOVE INTO THE WEST COAST MON NIGHT AND TUE.
THE EC IS STRONGER WITH THIS SYSTEM THAN IS THE GFS...AND SHOWS THE
ASSOCIATED SFC FRONTAL SYSTEM HOLDING TOGETHER ENOUGH TO BRING SOME
LIGHT RAIN TO AT LEAST SLO AND SBA COUNTIES LATE MON NIGHT AND TUE.
FOR NOW...HAVE KEPT POPS JUST BELOW SLIGHT CHANCE LEVELS DURING THIS
TIME PERIOD. IT SHOULD ME MOSTLY CLOUDY ACROSS THE REGION MON
NIGHT AND TUE...AND MAX TEMPS WILL BE DOWN SIGNIFICANTLY ON
TUE...LIKELY TO BELOW NORMAL LEVELS. THERE WILL BE A BROAD CYCLONIC
WNWLY FLOW PATTERN ALOFT FOR WED. THIS SHOULD MAINTAIN RATHER COOL
WEATHER ACROSS THE REGION. SOME WARMING MAY BEGIN ON THU AS HEIGHTS
ACROSS THE REGION BEGIN TO RISE SLIGHTLY.

&&

.AVIATION...18/1230Z...

MOST AIRFIELD LOCATIONS WILL BE DEALING WITH MVFR TO VFR CIGS OVER
THE NEXT 24 HOURS. MODERATE CONFIDENCE OVERALL WITH 12Z TAFS. THERE
WILL BE A 20 PERCENT OF THUNDERSTORMS DEVELOPING OVER THE LA/VTU
COUNTY MOUNTAINS AND ANTELOPE VALLEY. IF STORMS DO DEVELOP...THEY
WILL BE ELEVATED AND THE MAIN CONCERN BESIDES THE LIGHTNING WILL BE
THE DOWNDRAFT WINDS WHEN STORMS COLLAPSE. THEREFORE LLWS CAN`T BE
RULED OUT BETWEEN 18Z-06Z THIS EVE FOR THESE AREAS.

.KLAX AND KBUR...MODERATE CONFIDENCE WITH 12Z TAF OVER THE NEXT 24
HOURS. EXPECT MVFR TO VFR CIGS OVER THE NEXT 24 HOUR PERIOD. THERE
WILL BE A 15 PERCENT CHANCE OF IFR CONDS IF A FEW SHOWERS DEVELOP
AFTER 16Z TO 00Z THIS AFTERNOON.


&&

.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).

&&

$$

PUBLIC...DB
AVIATION...CAK

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