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[Printable]
563
FXUS66 KLOX 181751
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1050 AM PDT FRI APR 18 2014

UPDATED AVIATION DISCUSSION

.SYNOPSIS...

THE UPPER LOW OVER LOS ANGELES COUNTY BRINGING MORNING SHOWERS AND
DRIZZLE ALSO BRINGS A SLIGHT CHANCE OF THUNDERSTORMS TO THE
MOUNTAINS AND DESERTS THIS AFTERNOON AND EVENING.  WARMING OVER THE
WEEKEND...WITH TEMPERATURES ABOVE NORMAL BY SUNDAY. THEN COOLING AS
A TROUGH MOVES INTO THE WEST COAST LATE MONDAY.

&&

.SHORT TERM (TODAY-SUN)...THE UPPER LOW IS MOVING ONSHORE NEAR SAN
DIEGO THIS MORNING. WINDS ALOFT HAVE ALREADY SHIFTED TO THE NORTH
ACROSS THE WESTERN PORTION OF OUR FORECAST AREA AND THIS SHIFT WILL
PROPAGATE EAST ACROSS OUR CWA DURING THE MORNING HOURS. MARINE LYR
DEEPENED TO AROUND 4K FT AND DID GENERATE SOME DRIZZLE ALONG THE
FOOTHILLS. HIGH CLOUDS HAVE MOVED EAST BUT A DEEP LOW LVL MOIST
LAYER WILL LIKELY KEEP A FAIR AMOUNT OF CLOUDS AROUND THROUGH THE
AFTERNOON BELOW THE MARINE INVERSION BASE. TEMPS ALOFT NOT THAT
COLD, ONLY -17C AT 500MB, BUT MODELS DO SHOW A LITTLE INSTABILITY
WITH LI`S AROUND -2 AND CAPES 300-350 J/KG. SLIGHTLY BETTER
PARAMETERS TO OUR SOUTH WITH THE LOW CENTER AND IN THE SIERRA NEVADA
MTNS. BUT CAN`T RULE OUT AN ISOLATED SHOWER OR TSTORM OVER OUR MTNS
AND AV, WHICH IF THAT HAPPENS COULD DRIFT INTO THE VALLEYS WITH THE
LIGHT NORTHERLY FLOW.

***FROM PREVIOUS DISCUSSION***

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...18/1750Z.
HIGH CONFIDENCE IN WIDESPREAD MVFR TO VFR CIGS THROUGH 20Z. 20
PERCENT CHANCE OF SHOWERS AND THUNDERSTORMS FORMING OVER THE
MOUNTAINS AND ANTELOPE VALLEY THIS AFTERNOON NEAR KWJF AND KPMD AND
SURROUNDING MOUNTAINS. MARINE LAYER SHOULD BE MUCH LOWER TONIGHT
THAN TODAY...BUT THE CAPPING INVERSION MUCH WEAKER...WHICH SHOULD
LEAD TO MORE PATCHY COVERAGE OF CLOUDS AND LOWER CIGS AND VIS. LOW
CONFIDENCE HOWEVER ON EXACT DETAILS OF TIMING AND FLIGHT CATS.

.KLAX...HIGH CONFIDENCE IN SCT-BKN VFR CIGS ABOVE 030 TODAY.
MODERATE CONFIDENCE OF LOWER CIGS RETURNING TONIGHT...BUT LOW
CONFIDENCE IN TIMING AND DETAILS.

.KBUR...HIGH CONFIDENCE IN SCT-BKN VFR CIGS ABOVE 030 TODAY.
MODERATE CONFIDENCE OF LOWER CIGS RETURNING TONIGHT...BUT LOW
CONFIDENCE IN TIMING AND DETAILS.

&&

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

&&

$$

PUBLIC...MW/DB
AVIATION...KITTELL

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