FXUS66 KLOX 082159
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
200 PM PST TUE DEC 8 2009

.SYNOPSIS...

EXTREMELY COLD TEMPERATURES ARE EXPECTED TONIGHT AND AGAIN TUESDAY 
NIGHT. A STORM SYSTEM WILL BRING A CHANCE OF RAIN FOR THURSDAY...AND 
ANOTHER WEAKER STORM IS FORECASTED TO BRING RAIN INTO THE WEEKEND. 

&&

.SHORT TERM (TODAY-FRI)...ANOTHER COLD NIGHT IN STORE FOR SO CAL. 
LESS WIND TONIGHT SHOULD ACTUALLY BRING TEMPS DOWN A FEW DEGREES 
FROM LAST NIGHT DESPITE THE AIRMASS AS A WHOLE BEING SLIGHTLY 
WARMER. FROST ADVISORIES WILL BE POSTED FOR THE LA/VENTURA COUNTY 
VALLEYS AND VENTURA COUNTY COAST AS WELL AS THE CENTRAL COAST AGAIN 
TONIGHT. ISOLATED SHELTERED LOCATIONS IN VENTURA AND LA COUNTIES 
WILL DIP BELOW 28 TONIGHT BUT DECIDED THE AREAL COVERAGE OF SUB-28 
DEGREE READINGS (FOR MORE THAN 2 HOURS) WOULD NOT JUSTIFY THE 
STRONGER FREEZE WARNING PRODUCT. IN ANY CASE, PLENTY OF FROST 
TONIGHT AND AG INTERESTS ESPECIALLY SHOULD TAKE PRECAUTIONS TO 
MINIMIZE DAMAGE TO CROPS. 

A LITTLE UPPER LEVEL RIDGE OF HIGH PRESSURE CURRENTLY ALONG 140W 
WILL MOVE OVER THE AREA WED AND HELP WARM UP HIGHS A FEW DEGREES. 
HOWEVER, WE'LL START SEEING SOME HIGH CLOUDS SPREADING OVER THE AREA 
LATER TONIGHT WELL AHEAD OF OUR NEXT WEATHER SYSTEM. THIS WEATHER 
SYSTEM IS CURRENTLY JUST WEST OF THAT UPPER RIDGE AND MODELS 
INDICATE THE RIDGE WILL LIKELY WEAKEN IT CONSIDERABLY AS IT MOVES 
EAST. SO WHILE RAIN CHANCES ARE HIGH ON THURSDAY, IT'S NOT LOOKING 
LIKE IT WILL BE A MAJOR RAIN PRODUCER FOR US. ON AVERAGE RAINFALL 
AMOUNTS SHOULD RANGE FROM A QUARTER TO HALF INCH WITH UPSLOPE AREAS 
POSSIBLY GETTING CLOSE TO AN INCH. WITHOUT THE BENEFIT OF CONVECTION 
IT'S NOT LIKELY THIS STORM WILL POSE MUCH OF A THREAT TO BURN AREAS 
AND FLOOD WATCHES ARE NOT EXPECTED TO BE NEEDED. TIMING STILL 
SOMEWHAT OF AN ISSUE WITH THE GFS BEING MUCH FASTER THAN NAM. HAVE 
TRENDED TOWARDS THE SLOWER NAM FOR NOW, AND THIS HOLDS OFF RAIN IN 
LA/VENTURA COUNTIES UNTIL LATER IN THE DAY.

THE TRAJECTORY OF THIS STORM BEING FROM THE WEST WILL MEAN THAT SNOW 
LEVELS WILL BE CONSIDERABLY HIGHER THAN THIS LAST STORM. WE COULD 
INITIALLY SEE SNOW OR FROZEN PRECIP AT LOWER ELEVATIONS AS COLD AIR 
GETS TRAPPED BUT SNOW LEVELS WILL RISE RAPIDLY DURING THE EVENT 
THURSDAY INTO THURSDAY NIGHT AND WE HAVE THEM CONSERVATIVELY AROUND 
6000 FEET FOR NOW, THOUGH IT'S POSSIBLE IT COULD BE CLOSER TO 7000 
OR EVEN HIGHER.

THE LOW LVLS REMAIN QUITE MOST ON FRIDAY, BUT MOST OF THE DYNAMICS 
NEEDED TO GENERATE WIDESPREAD RAINFALL WILL HAVE MOVED ON. UPSLOPE 
AREAS WILL BE AT GREATEST RISK FOR SHOWERS, HOWEVER AT THIS STAGE OF 
THE FORECAST BEING 3 DAYS OUT WE CAN'T RULE OUT A SHOWER OR TWO JUST 
ABOUT ANYWHERE, HENCE THE LOW POPS CONTINUING THROUGH FRIDAY.

.LONG TERM (SAT-TUE)...SOME PRETTY SIZABLE DIFFERENCES IN THE GFS 
AND ECMWF FOR SAT, MAINLY WITH RESPECT TO THE PRECIP. TIMING IS 
SIMILAR ENOUGH ON THE MODELS SUCH THAT PRECIP CHANCES AGAIN ARE 
HIGH. THE ECMWF IS TAPPING INTO A MUCH DEEPER TROPICAL SOURCE OF 
MOISTURE WITH THIS STORM, AND THUS IS PUTTING OUT CONSIDERABLY MORE 
RAIN THAN THE GFS. GIVEN THAT THE ECMWF'S HANDLING OF THE LAST 
SYSTEM WAS VERY POOR AM INCLINED TO LEAN TOWARDS THE WEAKER GFS FOR 
NOW. THOUGH THE ECMWF'S SOLUTION IS CERTAINLY PLAUSIBLE AND WARRANTS 
CONSIDERATION. AS SUCH, THE SATURDAY STORM AT THIS POINT IN THE GAME 
HAS THE POTENTIAL FOR BEING A MUCH BETTER RAIN PRODUCER AND WE'LL 
HAVE TO MONITOR THE MODEL RUNS AND SATELLITE TO SEE IF THE MOISTURE 
TAP SETS UP ON SATURDAY. BEYOND SAT, THE ECMWF, GFS, AND CANADIAN 
MODELS INDICATE A DRYING TREND, ESPECIALLY BY MONDAY, WITH TEMPS 
WARMING TO AT OR EVEN ABOVE NORMALS BY THE MIDDLE OF NEXT WEEK.

&&

.AVIATION...08/1915Z.
VFR CONDITIONS EXPECTED INTO WEDNESDAY MORNING. NO AVIATION 
CONCERNS. 

KLAX AND KBUR...HIGH CONFIDENCE IN VFR CONDITIONS THROUGH WEDNESDAY 
MORNING.

&&

.LOX WATCHES/WARNINGS/ADVISORIES...
FREEZE WARNING (SEE LAXNPWLOX).
FROST ADVISORY (SEE LAXNPWLOX).
SMALL CRAFT ADVISORY (SEE LAXMWWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).

&&

$$

PUBLIC...WOFFORD
AVIATION...SWEET
SYNOPSIS...MEIER

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