FXUS66 KSGX 251704
AFDSGX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
905 AM PST WED NOV 25 2009
.SYNOPSIS...HIGH PRESSURE ALOFT AND OFFSHORE FLOW WILL BRING
CLEAR...WARM WEATHER TODAY AND THURSDAY. GUSTY NORTHEAST WILL
CONTINUE THROUGH AND BELOW THE MOUNTAIN CANYONS AND PASSES. A
STRONG...FAST MOVING TROUGH OF LOW PRESSURE WILL BRING COOLER
WEATHER FRIDAY AND A SLIGHT CHANCE OF LIGHT RAIN SATURDAY. A
POTENTIALLY STRONG OFFSHORE WIND EVENT IS POSSIBLE SUNDAY AND
MONDAY.
&&
.DISCUSSION...FOR SOUTHWEST CALIFORNIA INCLUDING SAN DIEGO...
ORANGE...SOUTHWEST SAN BERNARDINO AND WEST RIVERSIDE COUNTIES.
OFFSHORE WINDS GUSTING TO 20 TO 30 MPH WERE BLOWING THROUGH THE
MOUNTAIN PASSES THIS MORNING. THE STRONGEST WIND GUSTS OF 40-50 MPH
WERE LIMITED TO FREMONT CANYON IN THE THE SANTA ANA MOUNTAINS...NEAR
THE ANAHEIM HILLS FIRE.
THE WINDS KEPT MORNING LOW TEMPERATURES FROM FALLING TOO FAR AND
WERE IN THE 50S AND 60S. IN CONTRAST...WIND SHELTERED AREAS GOT
QUITE COLD (14 DEGREES AT BALDWIN LAKE).
THIS OFFSHORE WEATHER PATTERN DOES NOT CHANGE THROUGH THURSDAY WITH
UPPER LEVEL RIDGING AND SURFACE HIGH PRESSURE OVER THE GREAT BASIN.
DOUBLE DIGIT OFFSHORE SURFACE PRESSURE GRADIENTS WILL CONTINUE TO
BRING BLUSTERY NORTHEAST WINDS THROUGH THE PASSES. THE STRONGEST
WIND ARE LIKELY TO OCCUR LATE TONIGHT THROUGH THURSDAY MORNING.
THANKSGIVING DAY WILL BE A CARBON COPY OF TODAY WITH CLEAR SKIES AND
DAYTIME HIGHS 6 TO 12 DEGREES ABOVE AVERAGE. DURING THE AFTERNOON
SURFACE RIDGE BEGINS TO SHIFT EAST AND THE OFFSHORE WINDS WILL TAPER
OFF AS THE GRADIENTS WEAKEN. ONSHORE FLOW WILL INCREASE FRIDAY AHEAD
OF AN APPROACHING TROUGH THAT WILL BRING COOLER WEATHER AND A RETURN
OF SOME MARINE LAYER CLOUDS. THE MARINE LAYER WILL INITIALLY BE
QUITE SHALLOW AND PATCHY DENSE FOG IS POSSIBLE AT THE COAST DURING
THE DAY. THE 12Z NAM MODEL FORECASTS EXPLOSIVE GROWTH OF THE MARINE
LAYER FRIDAY NIGHT AND SATURDAY...DEEPENING TO OVER 5000 FEET
SATURDAY AFTERNOON. BOTH THE NAM AND GFS GENERATE AROUND A TENTH OF
AN INCH OF PRECIP.
IT HAS BEEN 161 DAYS SINCE MEASURABLE RAIN AT LINDBERGH FIELD. THE
LAST TIME IT RAINED WAS JUNE 16TH WHEN .03 INCHES FELL. THE LONG DRY
SPELL MAY END THIS WEEKEND. IF IT DOES NOT END AND MEASURABLE RAIN
DOES NOT FALL AT LINDBERGH FIELD...IT WILL MARK THE FIRST TIME A
STREAK OF DRY WEATHER THIS LONG HAS EXTENDED INTO THE MONTH OF
DECEMBER.
&&
.LONG TERM (SUNDAY-TUESDAY)...STRONG OFFSHORE FLOW FILLS IN BEHIND
THE UPPER LOW ON SUNDAY AND MONDAY. THE LATEST ECMWF...GFS AND DGEX
INDICATE NE WINDS OF 30-40 KT AT 850 MB WITH MODEST OFFSHORE
PRESSURE GRADIENTS. IT WILL STILL BE COOL THOUGH DUE TO COLD
ADVECTION FROM THE NORTH. MOSTLY CLEAR AND WARMER MONDAY AND
TUESDAY.
&&
.AVIATION...
251430Z...OFFSHORE FLOW WILL KEEP THE MARINE LAYER NEAR SEA LEVEL
THROUGH THANKSGIVING DAY. SOME RECOVERY IS EXPECTED ON FRIDAY. AS A
RESULT...A MOSTLY CLEAR SKY WITH UNRESTRICTED VISIBILITIES WILL
CONTINUE THROUGH THANKSGIVING. SOME VISIBILITY RESTRICTIONS CAN BE
EXPECTED IN THE VICINITY OF A WILDFIRE LOCATED IN THE SANTA ANA
RIVER CANYON BETWEEN KAJO AND KFUL.
LOCAL GUSTY NORTHEAST WINDS WITH ASSOCIATED UP AND DOWN DRAFTS AND
LOW LEVEL WIND SHEAR CAN BE EXPECTED BELOW PASSES AND CANYONS
THROUGH THANKSGIVING DAY. HORTON
&&
.MARINE...
MODERATE TO LARGE WNW SWELL TO ARRIVE THURSDAY NIGHT AND CONTINUE
THROUGH SATURDAY. WAMIII MODEL FOR SEVERAL DAYS HAS BEEN ADVERTISING
A RAPID INCREASE IN SWELL HEIGHTS LATE THURSDAY AFTERNOON/EVENING
REACHING 8 FT AT 16 SECONDS FROM 295 DEGREES OVERNIGHT/EARLY FRIDAY
MORNING. THE CURRENT OFFSHORE WIND FLOW PATTERN ENDS SHORTLY BEFORE
THIS AND CLIMATOLOGY FAVORS DENSE FOG NEAR SHORE AS FLOW RETURNS TO
ONSHORE. CONDITIONS COULD BE QUITE HAZARDOUS LATE THURSDAY THROUGH
FRIDAY MORNING ENTERING AND EXITING HARBORS AND BAYS. CONFIDENCE
FAIRLY HIGH IN HIGH SURF EVENT FRIDAY AND SATURDAY.
&&
.FIRE WEATHER...
AIRMASS VERY DRY THIS MORNING WITH HUMIDITIES ALREADY IN THE TEENS
AND 20S IN THE VALLEYS AND FOOTHILLS. PREVAILING SANTA ANA
CONDITIONS AND EFFICIENT DRYING OF FUELS THROUGH THURSDAY AFTERNOON.
HUMIDITY RECOVER WILL START THURSDAY NIGHT AND FRIDAY WHEN A SHALLOW
MARINE LAYER MOVES INLAND...DEEPENING TO ABOUT 5000 FEET THROUGH
SATURDAY WHEN LIGHT RAIN OR DRIZZLE IS POSSIBLE. THEN WE BRACE FOR
ANOTHER POTENTIALLY STRONGER OFFSHORE WIND EVENT SUNDAY AND MONDAY.
.SGX WATCHES/WARNINGS/ADVISORIES...
RED FLAG WARNING UNTIL 10 AM PST THURSDAY FOR THE SANTA ANA
MOUNTAINS AND FOOTHILLS. SEE LAXRFWSGX.
&&
$$
PUBLIC...MOEDE
AVIATION...HORTON
MARINE...BALFOUR
FIRE WEATHER...MOEDE
