FXUS66 KLOX 261700 CCA
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
900 AM PST SAT DEC 26 2009
...CORRECTED ISSUANCE TIME...
.SYNOPSIS...UPDATE...
A PAIR OF WEAK WEATHER SYSTEMS WILL AFFECT THE WEATHER ACROSS THE
REGION THROUGH SUNDAY NIGHT. CLOUDS...COOL TEMPERATURES...AND A
SMALL THREAT OF LIGHT RAIN WILL BE THE RULE DURING THE PERIOD. DRY
WEATHER IS EXPECTED TO RETURN MONDAY AND CONTINUE INTO THE NEW YEAR.
&&
.SHORT TERM (TODAY-MON)...UPDATE...
SATELLITE DATA SHOWS A BAND OF MOISTURE MOVING THROUGH CALIFORNIA
THIS MORNING...BRINGING WIDESPREAD HIGH CLOUDINESS TO THE REGION.
RADAR SHOWS SOME WEAK ECHOES WITH THIS SYSTEM MOVING DUE EAST AT
AROUND 30 KTS WITH THE HEAVIEST ECHOES APPROACHING SAN NICOLAS
ISLAND. NO PRECIPITATION IS BEING REPORTED WITH THIS BAND AND THE
12Z VANDENBERG SOUNDING SHOWED THE ATMOSPHERE TO BE VERY DRY THROUGH
ALMOST 500 MB. FURTHERMORE...THE BAND IS MOVING RAPIDLY INTO A
REGION OF VERY DRY AIR. THUS...DO NOT EXPECT TO SEE ANY SIGNIFICANT
PRECIPITATION WITH THE PASSAGE OF THESE CLOUDS AND ECHOES.
VAN NUYS HAD VISIBILITIES LESS THAN A QUARTER MILE FOR SEVERAL
PERIODS THIS MORNING...PROMPTING THE ISSUANCE OF A DENSE FOG
ADVISORY. VAN NUYS IS NOW REPORTING THREE MILES VISIBILITY WITH A
FOG BANK IN VICINITY. WHILE SOME LOCAL DENSE FOG CONDITIONS MAY
LINGER INTO THE NEXT HOUR...BELIEVE THAT THERE IS NO LONGER A NEED
FOR A DENSE FOG ADVISORY. THEREFORE...IT WILL BE ALLOWED TO EXPIRE
AT 9 AM.
...REMAINDER UNCHANGED...
LOTS OF HIGH CLOUDS PUSHING INTO THE FCST AREA. LOW CLOUDS SHOULD
BURN OFF TODAY...BUT THE 06Z WRF SUGGESTS A FAIR AMOUNT OF LINGERING
LOW LVL MOISTURE...SO WOULD NOT BE SHOCKED IF STRATUS HANGS TOUGH IN
SOME LOCATIONS. EVEN IF LOW CLOUDS BURN OFF...THERE SHOULD BE ENOUGH
HIGH CLOUDINESS TO WARRANT PARTLY CLOUDY WORDING. ACROSS SLO AND NRN
SBA COUNTIES...CLOUDS WILL PROBABLY BE THICK ENOUGH FOR MOSTLY
CLOUDY WORDING. THERE COULD BE A FEW SPRINKLES N OF PT CONCEPTION
THIS AFTERNOON AS A WEAKENING FRONTAL SYSTEM APCHS. THE COMBINATION
OF MORE CLOUDS...A RETURN TO ONSHORE GRADS...AND FALLING
HGHTS/THICKNESSES SHOULD LEAD TO SEVERAL DEGREES OF COOLING ACROSS
THE ENTIRE AREA TODAY.
AS THE UPPER LOW IN THE ERN PAC LIFTED NEWD TOWARD THE PAC NW LATER
TODAY AND TONIGHT...SUPPORT FOR THE SRN END OF ITS FRONTAL SYSTEM
WILL WEAKEN...AND THE FRONT WILL REALLY FALL APART QUICKLY AS IT
MOVES INTO THE CENTRAL COAST. STILL WILL KEEP SLIGHT CHANCE OR
CHANCE POPS FOR SLO AND NRN SBA COUNTIES TONIGHT AND EARLY SUNDAY.
ELSEWHERE...THERE WILL BE PLENTY OF HIGH AND MID LVL CLOUDS...AND
STRATUS WILL PROBABLY FORM AS WELL. FOR THE SAKE OF SIMPLICITY WILL
JUST GO MOSTLY CLOUDY ALL SECTIONS TONIGHT.
ANOTHER TROUGH WILL DROP SEWD THRU THE PAC ON SUNDAY...WITH BROAD
CYCLONIC FLOW ALOFT ACROSS THE FCST AREA AND A FAIR AMOUNT OF LOW
LVL MOISTURE AND WARM ADVECTION...ESPECIALLY ACROSS SLO AND SBA
COUNTIES. WILL KEEP CHANCE OF RAIN FOR THOSE AREA SUNDAY. L.A.
COUNTY AND MOST OF VTU COUNTY...SOME RIDGING AHEAD OF THE NEXT
TROUGH MAY ACTUALLY FORCE SOME OF THE THICKER CLOUDINESS TO THE
N...SO SKIES MAY BECOME PARTLY CLOUDY ON SUNDAY...AND TEMPS MAY EDGE
UP A FEW DEGREES.
ALL MODELS HAVE NOW CONVERGED ON THE MORE SLY TRACK OF THE UPPER
LOW...SHOWING IT PASSING WELL TO THE S AND W OF THE REGION SUNDAY
NIGHT AND EARLY MONDAY. SINCE IT MAY GET CLOSE ENOUGH TO GIVE THE
REGION A GLANCING BLOW...HAVE LEFT SLIGHT CHANCE IN ALL AREAS EXCEPT
FOR THE ANTELOPE VALLEY FOR SUNDAY NIGHT. THE GFS SHOWS SOME LIGHT
PRECIP ACROSS THE FCST AREA MONDAY INTO MON EVENING...POSSIBLY FROM
A NORTHERN STREAM UPPER LOW DROPPING SEWD THRU CA. THE ECMWF SHOWS
THIS AS WELL...BUT FOR MONDAY NIGHT. THE WRF IS BONE DRY ON
MONDAY...AND SHOWS DECENT LOW LVL NELY FLOW ACROSS THE AREA...WHICH
MAKES SENSE AS THE SFC LOW PASSES TO THE S. THIS SHOULD LEAD TO
DRYING AND WARMING W OF THE MTNS ON MONDAY...SO FOR NOW AM INCLINED
TO GO WITH A PTLY CLOUDY AND WARMER FCST FOR MONDAY.
.LONG TERM (TUE-FRI)...WHETHER THE TROUGH DROPPING SEWD THRU CA LATE
MON AND MON NIGHT HAS ENOUGH MOISTURE TO BRING SHOWERS TO PORTIONS
OF THE REGION REMAINS IN DOUBT. BEHIND THE SYSTEM...SEASONABLY COOL
WEATHER WILL RETURN TUE AS A MOSTLY DRY NWLY FLOW PATTERN ALOFT
SETS UP SRN CA. THE SRN END OF A WEAKENING FRONT COULD BRING A
SLIGHT CHANCE OF RAIN TO FAR NRN SXNS WED...BUT OVERALL IT LOOKS DRY
AND SEASONABLY COOL TUE THRU THU. SOME WARMING MAY BEGIN ON
THU...WITH MORE SIGNIFICANT WARMING EXPECTED ON NEW YEARS DAY AS A
RIDGE BUILDS INTO THE REGION.
&&
.AVIATION...26/1140...WEAK INVERSION IN PLACE MAKING A TOUGH
FORECAST FOR STRATUS THIS MORNING. HIGH CLOUDS MAKING IT TOUGH TO
SEE LOW CLOUDS FORMING BENEATH. HOWEVER...LOW TO MODERATE CONFIDENCE
FOR COASTAL TAFS AS MVFR CIGS FOR THE MOST PART THROUGH 17Z THIS
MORNING. EXPECT LIFR CONDS FOR KBUR AND KVNY THIS MORNING.
THERE WILL BE A CHANCE OF A FEW SHOWERS N OF POINT CONCEPTION LATER
THIS EVENING THROUGH THE OVERNIGHT HOURS. LOW CONFIDENCE WITH
STRATUS TIMING TO REDEVELOP TONIGHT.
KLAX...THERE IS A 60 PERCENT CHANCE THAT MVFR CIGS WILL DEVELOP AND
PERSIST THROUGH AT LEAST 17Z THIS MORNING. MODERATE CONFIDENCE FOR
BURNOFF BETWEEN 17-19Z THIS MORNING.
KBUR...MODERATE CONFIDENCE IN THE CURRENT TAF IN REGARDS TO TIMING
OF LIFR/IFR CIGS THIS MORNING. LOW CONFIDENCE IN ANY STRATUS
REFORMING TONIGHT.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
&&
$$
PUBLIC...BRUNO/DANIELSON
AVIATION...KAPLAN
SYNOPSIS...DB
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