AREA FORECAST DISCUSSION

 
 FXUS66 KSGX 232126
 AFDSGX
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE SAN DIEGO CA
 200 PM PST MON NOV 23 2009
 
 .SYNOPSIS...HIGH PRESSURE ALOFT AND WEAK OFFSHORE FLOW WILL BRING 
 FAIR WEATHER WITH A WARMING TREND THROUGH THANKSGIVING DAY. COOLER 
 WITH INCREASING CLOUDS TOWARD NEXT WEEKEND AS A LOW PRESSURE TROUGH 
 APPROACHES FROM THE NORTHWEST.
 
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 .DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO... 
 ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
 
 TODAY THROUGH THANKSGIVING DAY...CLEAR SKIES THIS AFTERNOON INTO 
 TONIGHT WITH SFC PRESSURE GRADIENTS OFFSHORE TO THE NORTH AND EAST 
 WITH ABOUT 9 MB SAN-TPH AND 1 MB SAN-IPL.
 
 AN UPPER LEVEL HIGH PRESSURE RIDGE AND A SFC HIGH OVER THE GREAT 
 BASIN WILL BRING FAIR SKIES...OFFSHORE FLOW...MUCH WARMER WEATHER 
 AND LOCAL GUSTY WINDS BELOW THE PASSES AND CANYONS THROUGH 
 THANKSGIVING DAY. INCREMENTAL INCREASES IN 500 MB HEIGHTS AND 850 MB 
 TEMPS WILL RESULT IN A FEW DEGREES OF WARMING EACH DAY...WITH 
 DAYTIME HIGHS REACHING ABOUT 10 DEGREES ABOVE SEASONAL AVERAGES BY 
 THANKSGIVING DAY. SKIES WILL BE MOSTLY CLEAR AS DRY OFFSHORE FLOW 
 SCOURS OUT THE MARINE LAYER.
 
 THE OFFSHORE FLOW WILL BE DRIVEN PRIMARILY BY SFC PRESSURE 
 GRADIENTS...WITH LITTLE UPPER LEVEL SUPPORT AND ONLY WEAK TO 
 MODERATE SFC PRESSURE GRADIENTS. WIND GUSTS BELOW THE PASSES AND 
 CANYONS WILL GENERALLY REMAIN BELOW 30 MPH...HOWEVER 
 ISOLATED/OCCASIONAL GUSTS FROM 40-50 MPH ARE POSSIBLE IN THE MOST 
 WIND-PRONE LOCATIONS. THE STRONGEST WINDS ARE EXPECTED TUESDAY 
 MORNING WHEN THE PRESSURE GRADIENTS ARE STRONGEST.
 
 VERY DRY AIR IS EXPECTED WITH THE OFFSHORE FLOW THIS WEEK. INLAND 
 HUMIDITIES WILL FALL BELOW 10 PERCENT EACH DAY BEGINNING TUESDAY AND 
 CONTINUING THROUGH THURSDAY. THE COMBINATION OF LOCALLY BREEZY 
 CONDITIONS AND VERY LOW HUMIDITIES WILL ELEVATE THE FIRE WEATHER 
 HAZARD.
 
 FRIDAY THROUGH MONDAY...THE GFS AND ECMWF PROGS FOR LATER THIS WEEK 
 ARE COMING INTO BETTER AGREEMENT AND SHOW THE RIDGE BREAKING DOWN 
 FRIDAY AHEAD OF A DEEPENING LOW PRESSURE TROUGH THAT WILL BRING 
 INCREASING CLOUDS AND SUBSTANTIAL COOLING THROUGH SATURDAY. AS THIS 
 TROUGH MOVES TO THE EAST ON SUNDAY AND MONDAY...A COLDER AND 
 POTENTIALLY WINDY OFFSHORE PATTERN COULD DEVELOP. 
 
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 .AVIATION...
 232000Z...CLEAR THROUGH TUESDAY WITH THIN HIGH CLOUDS AT TIMES. 
 OFFSHORE FLOW WILL INCREASE TONIGHT WITH NORTHEAST WINDS 15-25 KT 
 OVER THE MOUNTAINS AND INLAND VALLEYS THROUGH PASSES AND CANYONS 
 WITH MODERATE TURBULENCE THROUGH TUESDAY MORNING AND AGAIN TUESDAY 
 NIGHT THROUGH WEDNESDAY MORNING. 
 
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 .SGX WATCHES/WARNINGS/ADVISORIES...NONE.
 
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 $$
 
 PUBLIC...PG
 AVIATION...WHITLOW