AREA FORECAST DISCUSSION

FXUS66 KLOX 062247
AFDLOX

SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
245 PM PST TUE FEB 6 2007

.SHORT TERM...PATTERN SHIFT IN PROGRESS WITH UPPER RIDGE NOW WELL TO OUR EAST APPROACHING THE HIGH PLAINS AND A DEEP UPPER LOW APPROACHING THE WEST COAST. PRETTY SOLID JET ESTABLISHES ITSELF OVER APPROXIMATELY 30N WITH DISTURBANCES MOVING QUICKLY THROUGH THE EASTERN PACIFIC AND INTO CALIFORNIA FOR AT LEAST NEXT 7 DAYS OR SO...AND FAVORING LOCATIONS FROM THE CENTRAL COAST NORTHWARD. WILL BE DIFFICULT TO PIN DOWN TIMING OF INDIVIDUAL SYSTEMS UNTIL A COUPLE OF DAYS IN ADVANCE. THERE IS BASIC MODEL TO MODEL AGREEMENT THROUGH SATURDAY...THEN MODELS DIFFER ON SOLUTIONS SUNDAY INTO TUESDAY...AS USUAL. THEY ALL AGREE WE SHOULD BE IN AN UNSETTLED PATTERN FOR A WHILE...IT`S JUST A MATTER OF DIFFERENCES IN TIMING. RUN TO RUN DIFFERENCES APPEAR TO BE MINIMAL OUTSIDE OF USUAL OFF Z-TIME (18 AND 06Z) DIFFERENCES. WE`LL SEE A DECENT SUB TROPICAL FEED OF MOISTURE OUT OF THE CENTRAL PACIFIC AND PUSHING OUR PRECIPITABLE WATER AMOUNTS UP UP NEAR AN INCH STARTING THURSDAY AND REMAINING MOIST THROUGH AT LEAST SUNDAY.

FIRST SYSTEM STILL FORECAST TO MOVE THROUGH THE AREA SOMETIME TOMORROW. WE`RE SEEING THE IMPACT OF THIS SYSTEM IN THE FORM OF INCREASING CLOUDS OVER THE NEXT 12 HRS. BIGGEST DIFFERENCE BETWEEN GFS AND NAM-WRF APPEARS TO BE IN THE AMOUNT OF MOISTURE AND AS A RESULT PRECIPITATION EACH PRODUCES. MAIN TROUGH AXIS WILL MOVE THROUGH AROUND MIDDAY TOMORROW...FOLLOWED BY THE SURFACE FRONT SOMETIME AFTER THAT. COULD SEE SOME PREFRONTAL SHOWERS IN THE NORTH PRIOR TO 18Z. BEST UPPER LEVEL DYNAMICS MOVES BY IN THE AFTERNOON...BUT IT SHOULD BE A QUICK SHOT. STILL EXPECT MOST PRECIP TO FALL AFTER 18Z...AND QUITE POSSIBLY HOLDING OFF UNTIL LATER IN THE AFTERNOON. NAM-WRF KEEPS PRECIPITATION NORTH OF POINT CONCEPTION WHILE GFS PUTS LIGHT AMOUNTS SOUTH INTO VENTURA COUNTY. BOTH MODELS KEEP LA COUNTY DRY. HAVE DECIDED TO SHAVE BACK POPS A CATEGORY IN THE SOUTHERN VALLEYS FOR THIS FIRST SYSTEM...CLOSER TO MAV GUIDANCE. PROXIMITY TO BETTER MOISTURE FEED...PLUS SOME OROGRAPHICS WILL INCREASE CHANCES OF PRECIPITATION NORTH OF POINT CONCEPTION ESPECIALLY LATE TOMORROW. OVERALL EXPECT PRECIP AMOUNTS TO BE FAIRLY LIGHT WITH THIS FIRST SYSTEM.

WILL PROBABLY SEE A BRIEF BREAK IN THE SHOWERS EARLY THURSDAY BEFORE ANOTHER SYSTEM APPROACHES. MIGHT EVEN BE OVERDOING THE SLIGHT POPS IN THE SOUTH THURSDAY. GFS SHOWING A NICE WARM FRONT LIFTING NORTH AHEAD OF THE SYSTEM AND BRUSHING THE CENTRAL COAST THURSDAY NIGHT. HOWEVER...SYSTEM QUICKLY LIFTS TO THE NORTH INTO THE OREGON COAST OVERNIGHT THURSDAY...AND TAKING THE SURFACE COLD FRONT WITH IT. WENT AHEAD AND LEFT POPS ALONE FOR THE SOUTH ON THURSDAY NIGHT AND FRIDAY...BUT MAY HAVE TO DROP THOSE IN LATER SHIFTS DEPENDING ON HOW THE MODELS SEE IT. LATEST RUNS ACTUALLY PASS A WEAK RIDGE BY US FRIDAY EVENING. CENTRAL COAST REMAINS CLOSE ENOUGH TO THE MOIST JET TO CONTINUE PRECIPITATION CHANCES THURSDAY NIGHT INTO FRIDAY.

.LONG TERM (SAT-TUES)...

CENTRAL COAST REMAINS IN FAVORABLE LOCATION UNDER GOOD MOISTURE PLUME FROM THE SOUTHWEST ON SATURDAY. SOUTH OF POINT CONCEPTION SHOULD REMAIN MAINLY CLOUDY SATURDAY...BUT MOST LIKELY DRY. BY SATURDAY MIDDAY THE UPPER TROUGH AXIS SITS AT APPROXIMATELY 130W WITH GOOD SOUTHWEST FLOW INTO ALL OF CALIFORNIA. NAILING DOWN THE TIMING OF THE NEXT SYSTEM GETS TRICKY AT THIS POINT SINCE EXTENDED MODELS DIVERGE AFTER THAT...WITH THE UKMET AND ECMWF STAYING MORE OPEN AND PROGRESSIVE WHILE THE GFS CLOSES IT OFF BY 12Z SATURDAY. GFS EVENTUALLY MOVES SYSTEM THROUGH BUT NOT LIKELY UNTIL LATER SUNDAY. LEFT EXTENDED PRECIPITATION CHANCES ALONE FOR NOW GIVEN THIS UNCERTAINTY. AGAIN...QUESTION APPEARS TO BE WITH TIMING.

THEN IF YOU BELIEVE THE ECMWF WE SHOULD SEE SOME SLIGHT DRYING MONDAY IN WEAK RIDGING AHEAD OF ANOTHER SYSTEM IT FORECASTS TO MOVE THROUGH MONDAY NIGHT. GOOD MOIST JET REMAINS IN THE GFS THROUGH AT LEAST TUESDAY...THOUGH WITH NO PRONOUNCED UPPER LOW MOVING THROUGH. LEFT CHANCE POPS CENTRAL COAST...AND SLIGHT POPS SOUTH...ALONE FOR NOW.

OVER THE SEVEN DAY PERIOD...GFS STILL ADVERTISING GOOD PRECIP AMOUNTS IN THE CENTRAL COAST...POSSIBLY AROUND SEVERAL INCHES NORTHERN COASTAL SLO COUNTY...THEN TAILING OFF TO A QUARTER TO HALF INCH IN THE SOUTH. BOTTOM LINE IS WE SHOULD BE DONE WITH ANY OFF SHORE WIND EVENTS FOR A WHILE AT LEAST...WITH PRECIPITATION FAVORING THE CENTRAL COAST.

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.AVIATION...

AN APPROACHING COLD FRONT WILL BRING INCREASING CLOUDS THROUGH THE PERIOD WITH AIRFIELDS NORTH OF POINT CONCEPTION HAVING A CHANCE OF RAIN AND CIGS 050-100 AFTER 15Z WED. IN THE MEANTIME, SKIES WILL BE BKN200, EXCEPT FOR THE COASTAL WATERS AND IMMEDIATE COAST WHERE SCT-LCL BKN 003-008 WILL EXIST.

KLAX WILL SEE LIGHT WINDS UNDER 6 KT UNTIL A TYPICAL 10-12 KT WESTERLY SEABREEZE KICKS IN AROUND 20Z. A LOW CLOUD LAYER HOVERING ALONG THE COAST FROM KSMO SOUTH TO KLGB MAY SPREAD SOME SCT005-008 ONTO THE AIRFIELD THROUGH 20-21Z WITH VIS 4-6 MILES.

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.LOX WATCHES/WARNINGS/ADVISORIES...
NONE

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PUBLIC...JACKSON
AVIATION...WOFFORD