Area Forecast Discussion
Issued by NWS San Diego, CA

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000
FXUS66 KSGX 230446
AFDSGX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
846 PM PST MON DEC 22 2014

.SYNOPSIS...
A STRONG HIGH PRESSURE RIDGE ALONG THE WEST COAST WILL TEAM UP WITH
GUSTY OFFSHORE FLOW ALONG THE FOOTHILLS TO KEEP THE SKIES FAIR AND
THE DAYS WARM THROUGH WEDNESDAY. ON CHRISTMAS DAY...A FAST-MOVING
TROUGH WILL TOP THE RIDGE AND TURN THE WINDS BACK ONSHORE. STRONG
WESTERLY WIND GUSTS WILL DEVELOP OVER THE MOUNTAINS AND ON THE
DESERT SLOPES...AND A RAPIDLY DEEPENING MARINE LAYER MAY LEAK SOME
DRIZZLE OR SCATTERED...LIGHT RAIN SHOWERS WEST OF THE MOUNTAINS WITH
LITTLE ACCUMULATION IS EXPECTED. MUCH COOLER ON THURSDAY...THEN DRY
WITH SEASONAL TEMPERATURES FOR THE BALANCE OF THE HOLIDAY WEEKEND.
FOR EARLY NEXT WEEK...A DEEP TROUGH IS FORECAST OVER THE WEST. THIS
WILL BRING STRONG AND GUSTY WINDS...AND MUCH COLDER WEATHER.

&&

.DISCUSSION...FOR EXTREME SOUTHWESTERN CALIFORNIA INCLUDING ORANGE...
SAN DIEGO...WESTERN RIVERSIDE AND SOUTHWESTERN SAN BERNARDINO
COUNTIES...

PATCHY DENSE FOG POSSIBLE TONIGHT ALONG THE COASTAL STRIP

WIND ADVISORY FOR THE COASTAL SLOPES AND ADJACENT VALLEYS TONIGHT
AND TUESDAY

SCATTERED...LIGHT SHOWERS OR DRIZZLE POSSIBLE CHRISTMAS MORNING

STRONG WESTERLY WINDS OVER THE MOUNTAINS AND INTO THE DESERTS ON
CHRISTMAS DAY.

COLDEST WEATHER OF THE SEASON...AND MORE STRONG OFFSHORE WINDS
POSSIBLE WEST OF THE MOUNTAINS BY NEW YEARS EVE


A PATCH OF FOG WAS EVIDENT ON SATELLITE IMAGERY OVER THE COASTAL
WATERS BEFORE DARK...AND IR/FOG IMAGERY SHOWS PATCHES CONTINUE
ALONG THE COASTAL STRIP AND JUST OFFSHORE AT 8 PM PST. SURFACE
PRESSURE GRADIENTS WERE STILL WEAKLY ONSHORE TO THE LOWER DESERTS...
BUT WERE 6 MBS OFFSHORE FROM NV. REMOTE GAGES WERE JUST STARTING TO
RESPOND...THE 00Z MIRAMAR SOUNDING HAS REALLY DRIED OUT WITH PW
FALLING BELOW 1/2 INCH AND SHOWED SEVERAL MORE DEGREES C OF WARMING
BELOW 700 MBS COMPARED TO YESTERDAY AFTERNOON.

PATCHY DENSE FOG STILL LOOKS POSSIBLE DURING THE NIGHT ALONG THE
COAST ALTHOUGH SATELLITE TRENDS AND OBSERVATIONS HAVE NOT INDICATED
MUCH OF AN INCREASE. DEWPOINTS REMAIN ELEVATED ALONG THE COAST SO
THERE WILL BE A CHANCE OF FOG FORMING OVER THE NEXT FEW HOURS UNLESS
DRAINAGE WINDS ADVECT IN DRIER AIR.

A WIND ADVISORY HAS BEEN POSTED ALONG THE COASTAL SLOPES AND
EXTENDING INTO THE VALLEYS BEGINNING AT 10 PM THIS EVENING...AND
CONTINUING THROUGH WED MORNING. WINDS SHOULD PICK UP THROUGH THE
NIGHT AND PEAK TUE MORNING...EXCEPT ALONG THE SAN DIEGO COUNTY MTN
FOOTHILLS WHERE WINDS MAY NOT PEAK UNTIL LATE IN THE DAY OR DURING
THE EVENING. STRONGEST WINDS WILL BE LOCALIZED NEAR THE FOOTHILLS.

A STRONG HIGH PRESSURE RIDGE OVER THE EASTPAC HAS A RIDGE AXIS
EXTENDING NE ALONG THE WEST COAST. THE RIDGE WILL COLLAPSE
SOUTHEASTWARD AS A STRONG SHORTWAVE TROUGH SLIDES SE ACROSS CA WED
NIGHT/THU. THIS WAVE HAS LOOKED STRONGER WITH SUCCESSIVE MODEL RUNS
AND MAY END UP GENERATING A FEW LIGHT SHOWERS ALONG AND WEST OF THE
MTS LATE WED NIGHT INTO THU AM. IT WILL ALSO TURN AROUND THE
OFFSHORE FLOW AND DRIVE STRONG ONSHORE FLOW OVER THE MTN RIDGES AND
INTO THE DESERTS CHRISTMAS MORNING. A HIGH WIND WATCH MAY BE NEEDED
FOR THESE AREAS EARLY THU WITH LOCAL HIRES MODELS SHOWING STRONG MTN
WAVE ACTIVITY AND PEAK WESTERLY WIND GUSTS OVER 65 KTS ALONG THE
DESERT SLOPES. THESE WINDS WILL BE SHORT-LIVED AS THE TROUGH SLIDES
RAPIDLY SE AND SURFACE WINDS TURN BACK FROM THE NNE AND REMAIN GUSTY
IN WIND-PRONE AREAS. TEMPERATURES LOOK TO BE CLOSE TO AVERAGE FOR
LATE DECEMBER THROUGH THE HOLIDAY WEEKEND.

THE GFS MODEL HAS COME MORE IN LINE WITH THE COLD SOLUTIONS OF THE
ECMWF FOR EARLY NEXT WEEK. A SHARP TROUGH IS FORECAST TO DIG SOUTH
OVER CA. THE LATEST GFS MODEL HAS SFC-500 MB THICKNESS VALUES
FALLING BELOW 540 OVER SOCAL. EVEN IF WE GET CLOSE TO THOSE
VALUES...IT WILL MEAN THE COLDEST AIR OF THE SEASON BY NEW YEARS
EVE. STRONG...COLD...OFFSHORE WINDS TO THE COAST ARE POSSIBLE AS
WELL. THIS POTENTIAL WILL CONTINUE TO BE MONITORED AS WE GET CLOSER
TO THE EVENT.

&&

.AVIATION...
230400Z...SFC NE WIND GUSTS UP TO 55 KT...AREAS OF LLWS...AND
MOD-STG UDDFS POSSIBLE OVER AND SW OF THE MOUNTAINS THROUGH TUESDAY
NIGHT...INCLUDING VCNTY OF KONT AND KSNA...WITH LIGHTER WINDS
REACHING KCRQ. PATCHY DENSE FOG AFFECTING THE COASTAL WATERS AND 5
MI INLAND WITH VSBY AS LOW AS 1/2 SM THROUGH 08Z. OTHERWISE SKC AND
UNRESTRICTED VIS THROUGH TUE EVENING.

&&

.MARINE...
830 PM...NO HAZARDOUS MARINE WEATHER IS EXPECTED THROUGH SATURDAY.

&&

.BEACHES...
830 PM...A DECREASING W-NW SWELL WILL CONTINUE ELEVATED SURF
TONIGHT...WITH SETS TO 6 FT MAINLY IN SOUTHERN SAN DIEGO COUNTY. A
REINFORCING LONG-PERIOD W-NW SWELL WILL ARRIVE LATE TUE/EARLY
WED...LIKELY CONTINUING ELEVATED SURF AND STRONG RIP CURRENTS INTO
THURSDAY. MORNING HIGH TIDES AROUND 7 FT COULD CONTRIBUTE TO MINOR
TIDAL OVERFLOW THROUGH TUE. SEE THE BEACH HAZARD STATEMENT FOR
ADDITIONAL DETAILS...LAXCFWSGX.


&&

.FIRE WEATHER...
SURFACE HIGH PRESSURE BUILDING INTO THE GREAT BASIN WILL BRING
NORTHEASTERLY WINDS 20 TO 30 MPH WITH GUSTS TO 50 MPH TONIGHT
THROUGH WEDNESDAY MORNING. ISOLATED GUSTS TO 60 MPH OR MORE ARE
POSSIBLE AT SOME WIND PRONE LOCATIONS. MINIMUM RH WILL DROP TO
AROUND 20 PERCENT TUE AFTERNOON...WITH MODERATE RH RECOVERIES TUE
NIGHT. A TROUGH OF LOW PRESSURE WILL BRING GUSTY ONSHORE WINDS...
HIGHER RH VALUES...AND LOWER TEMPERATURES ON CHRISTMAS DAY.
INCREASED FUEL MOISTURE FROM RECENT PRECIPITATION WILL KEEP THE
WILDFIRE POTENTIAL LOW. WEAK TO MODERATE OFFSHORE FLOW WILL
REDEVELOP FRI INTO THE WEEKEND WITH LOWER RH RETURNING.

&&

.SKYWARN...
SKYWARN ACTIVATION WILL NOT BE NEEDED ON TUESDAY.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...BEACH HAZARDS STATEMENT THROUGH TUESDAY MORNING FOR THE BEACHES
     IN THE ORANGE COUNTY COASTAL AREAS...SAN DIEGO COUNTY
     COASTAL AREAS.

     WIND ADVISORY FROM 10 PM THIS EVENING TO 8 AM PST WEDNESDAY FOR
     THE ORANGE COUNTY COASTAL AREAS...RIVERSIDE COUNTY
     MOUNTAINS...SAN BERNARDINO COUNTY MOUNTAINS...SAN
     BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE...
     SAN DIEGO COUNTY MOUNTAINS...SAN DIEGO COUNTY VALLEYS...
     SANTA ANA MOUNTAINS AND FOOTHILLS.

PZ...NONE.

&&

$$

PUBLIC/FIRE WEATHER...JAD
AVIATION/MARINE...JMB







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