Area Forecast Discussion
Issued by NWS Los Angeles, CA

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FXUS66 KLOX 292106
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
200 PM PDT TUE JUL 29 2014

...MARINE DISCUSSION UPDATED...

.SYNOPSIS...

INCREASING TROPICAL MOISTURE WILL BRING CLOUDS AND A SMALL CHANCE OF
SHOWERS TO THE AREA LATER TONIGHT AND WEDNESDAY. BY AFTERNOON THAT
WILL SHIFT TO THE MOUNTAINS AND ANTELOPE VALLEY ALONG WITH A SLIGHT
CHANCE OF THUNDERSTORMS. THE TEMPERATURES WILL REMAIN ABOVE NORMAL
THROUGH FRIDAY...WITH SOME COOLING EXPECTED THIS WEEKEND INTO EARLY
NEXT WEEK.

&&

.SHORT TERM (TODAY-FRI)...MOISTURE FROM HERNAN WORKING ITS WAY NORTH
BUT HAVING MINIMAL IMPACT SO FAR. MOST MODELS SHOWING MOISTURE
INCREASING TONIGHT, ESPECIALLY THE WESTERN TWO THIRDS OF THE CWA,
BUT GENERALLY REMAINING ABOVE 600 MB. AT THE SAME TIME MODELS ALSO
INDICATE AN EMBEDDED SHORT WAVE MOVING INTO THE AREA, THOUGH NOT
SEEING ANY REFLECTION OF THIS SHORT WAVE IN SATELLITE IMAGERY. MAIN
DIFFERENCE IN THE MODELS IS THE LOCATION OF THE SHORT WAVE BY WED
MORNING, SOME HAVE IT AS FAR NORTH AS SLO COUNTY AND OTHERS OVER
VENTURA COUNTY. HAVE BEEN UNABLE TO FIND ANY EVIDENCE TO SUPPORT
CONVECTION OVERNIGHT, ELEVATED OR OTHERWISE, THOUGH MODELS
HISTORICALLY HAVE NOT HANDLED NORTHWARD PROPOGATING WAVES WELL,
PARTICULARLY THEIR MOISTURE AND STABILITY PARAMETERS. FOR NOW, GIVEN
THE AGREEMENT IN THE MODELS ON THE EXISTENCE OF A SHORT WAVE AND
AMPLE MOISTURE ALOFT HAVE DECIDED TO GO WITH A SLIGHT CHANCE OF
SHOWERS OVERNIGHT, MAINLY NORTHWEST OF A LINE FROM LAX-SAN CLEMENTE
ISLAND. IF IT STARTS TO LOOK MORE CONVECTIVE DURING THE EVENING
THUNDERSTORMS CAN BE ADDED.

SHOWER/CONVECTIVE THREAT WILL SHIFT INLAND DURING THE AFTERNOON
WEDNESDAY, WITH A MORE TRADITIONAL MTN/DESERT THUNDERSTORM FORECAST.
LIMITING FACTOR COULD BE THE THICK MID/HIGH LEVEL MOISTURE, THOUGH
MODELS ARE INDICATING THINNING OF THE MOISTURE BY AFTERNOON WHICH
SHOULD PERMIT ENOUGH SURFACE HEATING TO INITIATE CONVECTION.

HIGHS WEDNESDAY PROBABLY DOWN A FEW DEGREES FROM TODAY DUE TO THE
CLOUD COVER BUT COMPENSATED AT LEAST IN PART BY THE INCREASE IN
HUMIDITY, MAKING IT FEEL AS WARM IF NOT WARMER THAN TODAY.

A LITTLE LESS HUMIDITY THU/FRI AND NO THUNDERSTORMS EXPECTED BUT
WITH WARMER TEMPS DUE TO INCREASED SUNSHINE.

INCREASED NW FLOW WILL LEAD TO GUSTY WINDS THROUGH THE SANTA YNEZ
RANGE THE NEXT FEW NIGHTS. STRONGEST WINDS LIKELY THU EVENING,
POSSIBLY LOW END ADVISORY. ALSO QUITE WARM WITH TEMPS IN THE HIGH
80S OR LOW 90S NEAR THE BEACHES IN SRN SBA COUNTY, ESPECIALLY THU.

.LONG TERM (SAT-TUE)...LA COUNTY EXPECTED TO BE NEAR THE WESTWARD
EXTENT OF A PLUME OF MOISTURE STREAMING NORTH FROM MEXICO OVER THE
WEEKEND. GFS KEEPS THIS PLUME EAST WHILE THE ECMWF IS RIGHT ALONG
THE LA COUNTY BORDER. FOR NOW AM LEAVING THE FORECAST DRY BUT HAVE
ADDED SOME CLOUDS TO THE EASTERN PORTION OF OUR CWA AND SILENT POPS
(<15). A TROF MOVING INTO NRN CALIFORNIA OVER THE WEEKEND WILL BEGIN
A COOLING/DRYING TREND THAT WILL CONTINUE INTO EARLY NEXT WEEK. LOOK
FOR HIGHS DROP BACK TO NORMAL LEVELS BY MONDAY, IF NOT SOONER,
ESPECIALLY FOR SLO/SBA COUNTIES.

&&

.AVIATION...29/18Z

MODERATE CONFIDENCE IN THE 18Z TAFS WITH THE REDUCED CONFIDENCE DUE
TO THE UNCERTAINTY OF THE MARINE LAYER LOCATION... DURATION... AND
INTENSITY.

AREAS OF IFR/LIFR CIGS WILL RETURN TO THE CENTRAL COAST OVERNIGHT
AND INTO EARLY MORNING WITH A TWENTY PERCENT CHANCE OF IFR CIGS
ACROSS COASTAL SECTIONS OF LOS ANGELES AND VENTURA COUNTY 12Z-16Z.
OTHERWISE AND ELSEWHERE... VFR CONDITIONS ARE EXPECTED.

KLAX...MODERATE TO HIGH CONFIDENCE IN THE 18Z TAF. THERE IS A 20
PERCENT OF IFR CIGS BETWEEN 12Z AND 16Z... OTHERWISE VFR CONDITIONS
WILL PREVAIL THROUGHOUT THE FORECAST PERIOD.

KBUR...HIGH CONFIDENCE IN THE 18Z TAF.  VFR CONDITIONS WILL PREVAIL
THROUGHOUT THE FORECAST PERIOD.

&&

.MARINE...29/230 PM PDT

A SMALL CRAFT ADVISORY IS IN EFFECT THROUGH LATE TONIGHT IN ZONES
673 AND 676 WITH THE STRONGEST WINDS IN THE LATE AFTERNOON AND EARLY
EVENING HOURS.  STRONG WINDS MAY ALSO AFFECT THE WESTERN PORTION OF
ZONES 650 AND 655 AS WELL... AND WILL PERIODICALLY AFFECT THE REGION
THROUGH FRIDAY.  OFFSHORE WINDS WILL LIKELY AFFECT THE WATERS
IMMEDIATELY SURROUNDING THE SANTA BARBARA COAST THURSDAY NIGHT AND
EARLY FRIDAY MORNING.
&&

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

&&

$$

PUBLIC...MW
AVIATION...KJ
MARINE...KJ

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