FXUS66 KLOX 071825
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
1025 AM PST MON DEC 7 2009
UPDATED AVIATION DISCUSSION
.SYNOPSIS...
A COLD LOW PRESSURE SYSTEM WILL BRING WINDS...RAIN...AND LOW
ELEVATION SNOW TO THE AREA TODAY THROUGH TUESDAY MORNING. A SERIES
OF SYSTEMS WILL BRING MORE CHANCES OF RAIN TO THE AREA FROM THURSDAY
THROUGH THE WEEKEND. TEMPERATURES WILL REMAIN WELL BELOW SEASONAL
NORMALS THROUGH THE WEEK...COLDEST TODAY AND TUESDAY.
&&
.SHORT TERM (TODAY-WED)...
RAIN HAS ARRIVED ON SCHEDULE THIS MORNING. 12Z MODELS CONTINUE TO
SHIFT THE EMPHASIS OF THE HEAVIER RAIN SOUTH AND EAST OF LA COUNTY
WITH THE UPPER JET SO IT'S LOOKING MORE AND MORE THAT OUR CWA WILL
BE SPARED THE HEAVIEST RAIN THAT PREVIOUS RUNS HAD SHOWN FURTHER
NORTH. THE FIRST BATCH OF RAIN IS MOVING THROUGH NOW WITH GENERALLY
LIGHT TO LOCALLY MODERATE RATES (MOSTLY .10-.20 IN/HR). FOR AREAS
SOUTH OF PT CONCEPTION THERE WILL LIKELY BE A 2-4 HOUR DECREASE IN
RAINFALL RATES AND AREAL COVERAGE LATER THIS MORNING INTO EARLY
AFTERNOON BEFORE THE COLD FRONT ARRIVES. THIS BREAK WILL BE MINIMAL
FOR THE CENTRAL COAST AS THE LEADING EDGE OF THE FRONT IS ALREADY
MOVING INTO SLO COUNTY AT THIS TIME. WILL LEAVE THE FLOOD WATCH UP
FOR THE LA COUNTY BURN AREAS AS RAINFALL RATES COULD BRIEFLY EXCEED
USGS THRESHOLDS WHEN THE COLD FRONT ARRIVES LATER THIS AFTERNOON,
BUT OVERALL RAINFALL AMOUNTS WITH THIS STORM WILL NOT BE AS HIGH AS
EARLIER THOUGHT. REFERENCE THE LATEST QPS PRODUCT (TO BE UPDATED
SHORTLY) FOR MORE INFO ON EXPECTED STORM TOTALS. REMAINDER OF
FORECAST LOOKS GOOD. HEAVY SNOW STILL EXPECTED FOR THE GRAPEVINE AND
AREAS NEAR THE KERN COUNTY LINE TONIGHT INTO EARLY TUESDAY WITH LOW
SNOW LEVELS. GUSTY WINDS BEHIND THE FRONT WILL LIKELY REQUIRE WIND
ADVISORY FOR MANY AREAS THIS EVENING.
***FROM PREVIOUS DISCUSSION***
THE WEATHER BEHIND THE COLD FRONT WILL BE INTERESTING. BY 06Z 537DM
THKNS ARE FORECAST THROUGH HALF OF THE COUNTY WITH 543 DM THKNS OVER
KLAX. THIS AMOUNT OF COLD AIR ADVECTION WILL BRING IN QUITE A BIT OF
GUSTY NW WINDS AND WIND ADVISORIES MAY WELL BE NEEDED FOR MANY AREAS
OF SLO AND SBA COUNTY. NO WIND PRODUCTS FOR THE MTNS OF LA AND VTA
COUNTY SINCE THE WINDS ARE WRAPPED UP IN THE WINTER STORM WARNING
BUT GUSTS TO 55 MPH WILL OCCUR BEHIND THE FRONT. THESE KINDS OF
THKNS WILL LOWER THE SNOW LEVELS TO 2000 FEET OR LOWER. BUT SINCE IT
IS QUITE DRY BEHIND THE FRONT THE AMOUNT OF SNOW FALL WILL BE
LIMITED AND MOSTLY CONFINED TO THE NORTHERN SLOPES AND INTERIOR VLYS
AS WELL AS THE FOOTHILLS OF THE ANTELOPE VLY. LOW TEMPS AND
POTENTIAL FROST AND FREEZE ISSUES WILL BE A MAJOR CONCERN TONIGHT
GUSTY WINDS WILL KEEP MOST TEMPS EVERYWHERE EXCEPT THE SOUTHERN
COASTAL ZONES IN THE MID 30S BUT ANY WIND SHELTERED AREAS COULD
EASILY SEE MIN TEMPS IN THE MID TO UPPER 20S.
TUESDAY WILL BE PARTLY CLOUDY OR EVEN MOSTLY SUNNY BEHIND THE
FRONT...BUT IT WILL BE COLD DESPITE SEEING SOME SUNSHINE MAX TEMPS
WILL BE ABOUT 15 DEGREES COLDER THAN NORMAL. CLOUDS AND SNOW SHOWERS
WILL CONTINUE ON THE NORTH SLOPES IN THE MORNING BEFORE DISSIPATING
IN THE AFTERNOON.
WEDNESDAY WILL BE A DECENT IF NOT SOME WHAT COOL DAY. A SMALL RIDGE
POPS UP AND TEMPS WILL RISE ABOUT 8 DEGREES FROM TUESDAYS VALUES.
SKIES WILL BE PARTLY CLOUDY AS MID AND HIGH LEVEL CLOUDS FROM AN
APPROACHING STORM DRIFT THROUGH THE RIDGE.
.LONG TERM (THU-SUN)...
THE GFS AND THE EC ARE IN GOOD SYNOPTIC AGREEMENT FOR THE EXTENDED
PERIOD BUT DISAGREE SOMEWHAT ON THE TIMING...LOCATION AND AMOUNTS OF
RAIN. BUT BOTH AGREE THAT THE RAIN DOOR IS OPEN. BOTH MDLS AGREE
THAT THE RIDGE WILL BREAK DOWN INTO A WESTERLY FLOW PATTERN THURSDAY
AND THAT THIS PATTERN WILL LAST THROUGH SUNDAY WITH PERHAPS A LITTLE
WAVE MOVING THROUGH SUNDAY.
THE EC FORECAST LIGHT RAIN THU AND FRI WITH HEAVIER SATURDAY AND
SUNDAY. THE GFS BRINGS LIGHT RAIN INTO THE AREA THURSDAY AND THEN
NOTHING ON FRIDAY. A LITTLE HEAVIER RAIN ON SATURDAY AND THEN
FORECASTS A MAJOR RAIN EVENT SUNDAY.
THINK WE CAN SAFELY SAY THAT WE WILL HAVE A LIGHT RAIN EVENT
THURSDAY WITH MAYBE A QUARTER TO A HALF INCH OF RAIN. SNOW LEVELS
WILL BE HIGHER THAN TODAYS STORM.
LEFT A CHANCE OF RAIN IN FOR FRIDAY. WILL JUST GIVE CHC RAIN FOR THE
WEEKEND SEEING HOW FAR OUT THE FCST IS AND THE MDLS PROPENSITY TO
CHANGE A FORECAST MAJOR STORM INTO A WEAKER ONE WITH TIME. BUT IT
WILL BE INTERESTING TO SEE HOW THESE SYSTEMS PLAY OUT.
&&
.AVIATION...07/1820Z.
CONFIDENT IN RAINY AND WINDY TAF PERIOD. MODERATE TO LOW CONFIDENCE
ON EXACT TIMING OF HEAVIEST RAIN...BUT TEMPO PERIODS SHOULD COVER
IT. MOSTLY MVFR CATS THROUGH THIS EVENING...WITH IFR CATS FOR A FEW
HOURS DURING HEAVIEST RAINS. MODERATE TO HIGH CONFIDENCE ON WIND
SPEEDS...AND LLWS MAY BE A CONCERN...WILL UPDATE TAFS IF REPORTS
START COMING IN. TIMING OF WIND ACCELERATION IS PLUS OR MINUS 3
HOURS.
KLAX...MODERATE CONFIDENCE IN OCCASIONAL IFR CATS WITH HEAVIEST RAIN
BETWEEN 21-02Z...OTHERWISE MODERATE CONFIDENCE IN MVFR CATS
PREVAILING THROUGH THIS EVENING. EAST TO SOUTHEAST WINDS WILL STICK
AROUND 10 KTS THROUGH ABOUT 22Z...THEN SHIFT TO THE WEST BY 02Z.
WEST WINDS WILL BE STRONG WITH GUSTS IN THE 30KT RANGE. LLWS MAY BE
A CONCERN WITH THE WEST WINDS. THROUGH LOW CONFIDENCE IN EXACT
CIG/VIS FCST DURING THE RAIN AS BOTH VALUES WILL CHANGE FROM ONE
MOMENT TO THE NEXT. EXPECT IFR TO LOW MVFR CONDS. EAST WINDS AROUND
10 KTS ARE LIKELY DURING THE MORNING WITH A 30 PERCENT CHANCE OF
ARRIVING BY 12Z.
KBUR...MODERATE CONFIDENCE IN IFR CATS WITH HEAVIEST RAIN BETWEEN
21-02Z...OTHERWISE MODERATE CONFIDENCE IN MVFR CATS PREVAILING
THROUGH THIS EVENING. MODERATE CONFIDENCE IN NORTHWEST WINDS GUSTING
INTO THE 20KT RANGE AFTER ABOUT 03Z...WITH LLWS POSSIBLY A CONCERN.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
WINTER STORM WARNING (SEE LAXWSWLOX).
HIGH WIND WATCH (SEE LAXNPWLOX).
FLASH FLOOD WATCH (SEE LAXFFALOX).
GALE WARNING (SEE LAXMWWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
MARINE WEATHER STATEMENT (SEE LAXMWSLOX).
&&
$$
PUBLIC...WOFFORD/RORKE
AVIATION...KITTELL
SYNOPSIS...ASR
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