FXUS66 KLOX 040552 AAA
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
952 PM PST THU DEC 3 2009
...UPDATED AVIATION SECTION...
.SYNOPSIS...
FRIDAY IS EXPECTED TO WARM TO NEAR SEASONAL TEMPERATURES. SATURDAY
WILL BEGIN A COOLING TREND WITH ONSHORE BREEZES. A LOW PRESSURE
SYSTEM WILL BEGIN MOVING INTO THE REGION SUNDAY WITH A SLIGHT
CHANCE OF RAIN SHOWERS...INCREASING TO RAIN LIKELY ON MONDAY..AND A
CONTINUING CHANCE OF RAIN AT TIMES THROUGH THURSDAY...ALONG WITH
COOLER TEMPERATURES.
&&
.SHORT TERM (TONIGHT-SUN)...MARINE LAYER NEAR 1200 FT DEEP AT LAX
THIS EVENING. PATCHY LOW CLOUDS WERE NEAR THE COAST FROM VTU TO L.A.
COUNTIES AND SOME MAY CONTINUE MOVING INLAND FOR A WHILE THIS
EVENING OTHERWISE INCREASING OFFSHORE FLOW WILL PUSH THE MARINE
LAYER CLOUDS OFF THE COAST OVERNIGHT. THE SAME IS EXPECTED FOR THE
LOW CLOUDS THAT WERE OVER THE CENTRAL COAST INTO THE SANTA YNEZ
VALLEY THIS EVENING AS WELL. OTHERWISE IT LOOKS LIKE MOSTLY CLEAR
SKIES WILL COVER MOST OF THE FORECAST AREA THRU THE NIGHT. WITH
OFFSHORE GRADIENTS INCREASING OVERNIGHT...NE CANYON WINDS ARE
EXPECTED TO BECOME GUSTY AFTER MIDNIGHT ESPECIALLY OVER VTU/L.A.
COUNTIES...BUT WINDS ARE EXPECTED TO REMAIN GENERALLY BELOW ADVISORY
LEVELS AS SUPPORT FOR STRONG WINDS IS LACKING.
AN UPPER RIDGE ALONG THE CA COAST TONIGHT WILL WEAKEN WHILE MOVING
INLAND OVER SOUTHERN CA ON FRI. BROAD UPPER TROFFINESS IS EXPECTED
TO MOVE INTO THE REGION FRI NIGHT AND SAT...THEN LINGER OVER THE
AREA THRU SUN....WITH A BROAD W TO NW FLOW ALOFT. IT LOOKS LIKE THE
MARINE LAYER WILL REMAIN DISORGANIZED FRI THU SAT...WITH PERHAPS
SOME LOW CLOUDS AT TIMES ON THE CENTRAL COAST FRI NIGHT INTO SAT
MORNING...OTHERWISE SKIES WILL BE MOSTLY CLEAR THRU FRI THEN SOME HI
CLOUDS SHOULD MOVE OVER THE FORECAST AREA FRI NIGHT AND SAT FOR
PARTLY CLOUDY CONDITIONS AT TIMES. THE MARINE LAYER IS EXPECTED TO
BECOME BETTER ORGANIZED AND DEEPEN SIGNIFICANTLY SAT NIGHT INTO SUN
MORNING IN RESPONSE TO INCREASING ONSHORE FLOW AND THE UPPER LEVEL
TROFFINESS. THE DEEPENING MARINE LAYER WILL ALSO BRING THE SLIGHT
CHANCE TO CHANCE OF SHOWERS TO THE COAST/VLYS AND LOWER COASTAL
SLOPES OF VTU/L.A. COUNTIES BY EARLY SUN AND FOR MUCH OF THE DAY.
OTHERWISE DRY WEATHER IS EXPECTED ACROSS THE REGION THRU SUN. TEMPS
ARE EXPECTED TO WARM TO NEAR SEASONAL NORMS FOR FRI...THEN COOL BACK
TO A FEW DEGREES BELOW NORMAL FOR SAT...AND SIGNIFICANTLY BELOW
NORMAL FOR SUN.
...FROM PREVIOUS DISCUSSION...
.LONG TERM (SUN NIGHT-THU)...UNFORTUNATELY THE 12Z MODEL RUNS REALLY
OFFERED NOTHING NEW IN TERMS OF RESOLVING THE ISSUES WITH NEXT
WEEK'S FORECAST. ALL THE MODELS CONTINUE TO HANG TIGHT TO THEIR
RESPECTIVE WET/DRY SOLUTIONS, WITH THE GFS/CANADIAN CONTINUING TO
INDICATE A DRIER/COLDER PATTERN WHILE THE ECMWF IS WARMER AND
WETTER. IT'S STILL TOO EARLY TO HAVE ANY CONFIDENCE WITH ANY
SPECIFIC SOLUTION SO THE FORECAST IS STILL RIFE WITH UNCERTAINTY.
THE GOOD NEWS IS THAT ALL THE MODELS AGREE ON AT LEAST SOME RAIN FOR
MONDAY, THOUGH THE SPECIFICS ARE VERY MUCH IN DOUBT. THE GFS IS MUCH
COLDER WITH THE MONDAY SYSTEM AS IT DROPS THAT COLD UPPER LOW SOUTH
INTO CALIFORNIA WITH A FAST MOVING COLD FRONT MOVING THROUGH DURING
THE DAY. THIS WOULD BRING US A QUICK SHOT OF RAIN WITH RAPIDLY
LOWERING SNOW LEVELS. CURRENT FORECAST IS NOT NEARLY THIS COLD AND
WOULD NEED SIGNIFICANT ADJUSTMENTS IF THE GFS TURNS OUT TO BE
CORRECT. NONE OF THE SOLUTIONS FOR MONDAY SUGGEST MORE THAN A LIGHT
TO OCCASIONALLY MODERATE PRECIPITATION EVENT. IN ANY CASE, OUR
CONFIDENCE LEVELS ARE HIGHEST FOR PRECIP ON MONDAY AND THE FORECAST
POPS REFLECT THAT.
CONFIDENCE MUCH LOWER FOR THE TUE-THU TIME FRAME. THE GFS/CANADIAN
SOLUTION IS BONE DRY FOR TUE AND THE FIRST HALF OF WED WHILE THE
ECMWF KEEPS THE AREA IN A MOIST WEST/SOUTHWEST FLOW PATTERN THROUGH
THE PERIOD. ABOUT THE BEST WE CAN DO AT THIS EARLY STAGE IS KEEP IN
SOME CHANCE OF PRECIP AND WAIT FOR HOPEFULLY BETTER CONSENSUS SOON.
&&
.AVIATION...04/0552Z...VFR CONDITIONS WILL DEVELOP AT ALL TERMINALS
BY 10Z TONIGHT. HOWEVER...THERE IS A SLIGHT CHANCE THAT CONDITIONS
COULD DETERIORATE TO VLIFR TO LIFR AFTER 08Z TONIGHT AT TERMINALS
NORTH OF POINT CONCEPTION. IF VLIFR TO IFR CONDITIONS
DEVELOP...CONDITIONS WILL LIKELY PERSIST THROUGH AROUND 16Z ON
THURSDAY MORNING.
KLAX...VFR CONDITIONS ARE EXPECTED THROUGH THE NEXT 24 HOURS WITH
ANY OFFSHORE WINDS REMAINING LESS THAN 10 KNOTS. THERE IS A SLIGHT
CHANCE OF VLIFR IN THE VICINITY OF KLAX AFTER 07Z FRIDAY NIGHT.
KBUR...VFR CONDITIONS ARE EXPECTED THROUGHOUT THE PERIOD WITH LIGHT
TURBULENCE POSSIBLE THROUGH 13Z.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
NONE
&&
$$
PUBLIC...SIRARD/WOFFORD
AVIATION...HALL
SYNOPSIS...SETO
WWW.WEATHER.GOV/LOSANGELES
