Frost Advisory 1, NWS San Diego, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
115 PM PST MON DEC 31 2012

.SYNOPSIS...
A WEAK DISTURBANCE WILL DRIFT OVER THE REGION TONIGHT WITH SOME HIGH
CLOUDS...AND CONTINUED QUITE COOL WITH PATCHY FROST REDEVELOPING
WEST OF THE MOUNTAINS AND IN THE COACHELLA VALLEY. OTHERWISE...HIGH
PRESSURE WILL SLOWLY BUILD OVER CALIFORNIA THIS WEEK BRINGING
OFFSHORE FLOW AND SUNNY...WARMER DAYS.

&&

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

IT WAS A VERY CHILLY MORNING ACROSS THE REGION UNDER CLEAR SKIES
WITH A LIGHT COATING OF SNOW OVER THE MOUNTAINS. MUCH OF THE SNOW
MELTED QUICKLY BY AFTERNOON AT LOWER ELEVATIONS. SEE LAXRRMSGX...OR
THE HEADLINE LINK ON OUR WEB PAGE FOR RAIN AND SNOW TOTALS. SURFACE
PRESSURE GRADIENTS REMAINED WEAK...BUT A FEW PASSES AND CANYONS HAD
SOME NE WINDS WITH GUSTS UP TO 30 MPH EARLIER IN THE DAY. DEWPOINTS
WERE IN THE 30S W OF THE MTNS SO RH WAS LOWER TODAY AND WILL
CONTRIBUTE TO RAPIDLY FALLING TEMPERATURES THIS EVENING. SKIES WERE
SUNNY...BUT A FEW HIGH CLOUDS WERE BEGINNING TO FILTER IN FROM THE
NORTH.

AN UPPER-LEVEL TROUGH OVER THE WEST WILL PULL EAST TODAY...ALLOWING
HEIGHTS/THICKNESS TO RISE. AT THE SAME TIME ANOTHER IMPULSE WILL
DROP DOWN THE W SIDE OF THE TROUGH ON TUE IN THE DRY...CONTINENTAL
AIR MASS OVERHEAD. IT IS NOT EXPECTED TO GENERATE ANY PRECIP HERE...
BUT WILL REINFORCE THE OFFSHORE FLOW AND DRYING OVER THE AREA. NE
WINDS WILL INCREASE AND BECOME GUSTY THROUGH THE OFFSHORE...WIND
PRONE PASSES AND CANYONS TUE THROUGH THU. THE OFFSHORE FLOW WILL
BRING WARMING TO COASTAL AREAS...PUSHING MAX TEMPS BACK ABOVE NORMAL
AT THE COAST FOR THE FIRST TIME IN SEVERAL WEEKS. THE NIGHTS WILL
REMAIN AT OR BELOW NORMAL DUE TO THE DRY AIR AND LIGHT WINDS.

THE MAIN NEAR-TERM FORECAST CONCERN WILL BE FOR FROST OVERNIGHT.
EXPECT THERE WILL BE SOME AGAIN WEST OF THE MTNS AND IN THE
COACHELLA VALLEY AGAIN...BUT SHOULD NOT BE AS WIDESPREAD AS LAST
NIGHT DUE TO BETTER LATE DAY SFC HEATING...THICKENING HIGH CLOUDS
OVERSPREADING THE AREA FORM THE NORTH...AND CONSIDERABLY HIGHER
THICKNESS VALUES. SOME FROST IS STILL LIKELY THOUGH...AND IS
INCLUDED IN THE FORECAST. AFTER TUE MORNING...THE FOCUS WILL SHIFT
TO WIND. FOR NOW...MODELS...AND THE LOCAL WIND PROGRAM SHOWS GUSTS
TO ADVISORY STRENGTH (45-50 MPH) ARE LIKELY THROUGH THE WIND PRONE
PASSES AND CANYONS ON WED. AN ADVISORY WILL LIKELY BE ISSUED TO
ADDRESS THIS WITHIN 24 HOURS.

THE MODELS ARE IN FAIRLY GOOD AGREEMENT THROUGH THIS WEEK...THEN
CONSIDERABLE DIVERGENCE DEVELOPS LATE NEXT WEEKEND...MAINLY WITH THE
GFS RUNS AND SOME ENSEMBLE MEMBERS OF THE ECMWF. THE 12Z GFS IS
DIGGING AN UPPER LOW OFF THE CA COAST NEXT MON...AND SWINGING IT
EAST ACROSS SOCAL NEXT TUE. THIS RUN FAVORS SOME PCPN HERE EARLY
NEXT WEEK AS THE LOW BECOMES NEARLY CUT-OFF. THE 00Z GEM AND 12Z
OPERATIONAL ECMWF MODELS VARY...THE ECMWF KEEPS THIS FEATURE WEAKER
AND MORE PROGRESSIVE...WHILE THE GEM DIGS IT FARTHER EAST. BOTH
THESE SOLUTIONS KEEP SOCAL DRY UNDER A STRONG HIGH PRESSURE RIDGE.
TO ADD TO THE UNCERTAINTY...THE APPARENT OUTLYING SOLUTION OF THE
OPERATIONAL GFS DOES HAVE SOME SUPPORT FROM A FEW OF THE ECMWF
ENSEMBLE RUNS. IN ANY CASE...ANY DEVIATION FROM THE COURSE PLOTTED
WOULD PROBABLY KEEP US DRY UNDER THE LARGE RIDGE BUILDING ACROSS THE
EAST PACIFIC AND WESTERN U.S. SO CHANCES LOOK SLIM AT THIS POINT AND
ARE NOT MENTIONED IN THE AFTERNOON ZONE FORECAST PACKAGE.

&&

.AVIATION...
312100Z...FEW/SCT HIGH CLOUDS THROUGH TUE MORNING. OTHERWISE...HIGH
PRESSURE OVER THE REGION WILL CREATE VFR CONDS THROUGH THE TAF
PERIOD.

&&

.MARINE...
A LARGER WNW SWELL WILL ARRIVE TO THE COASTAL WATERS TUE
MORNING...WITH 4-6 FT/16 SEC PERIOD WAVES FORECAST TO REACH THE
SOUTHERN SAN DIEGO COUNTY COAST BY LATE TUE MORNING. SURF 5-7 FT
WILL BE POSSIBLE WITH SETS TO 8 FT...MAINLY SOUTH OF CARLSBAD.
THEREFORE...A HIGH SURF ADVISORY HAS BEEN ISSUED FOR 10 AM TUE
THROUGH 4 PM PST WED FOR SAN DIEGO COUNTY BEACHES. 7 FT SETS SHOULD
BE ISOLATED BY LATE WED AFTERNOON AS THE SWELL BEGINS TO LOWER.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...
CA...HIGH SURF ADVISORY FROM 10 AM TUESDAY TO 4 PM PST WEDNESDAY FOR
     THE SAN DIEGO COUNTY COASTAL AREAS.

PZ...NONE.

&&

PUBLIC...JAD
AVIATION/MARINE...JJT

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PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE SAN DIEGO CA
356 PM PST MON DEC 31 2012

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0935 PM     WATER SPOUT      18 SW SAN CLEMENTE      33.26N 117.83W
12/29/2012                   PZZ750             CA   UTILITY COMPANY

            SATURDAY 12/29/12... LATE REPORT 935 AM WEST OF SAN
            ONOFRE THE OBSERVER COULD SEE A CLEAR FUNNEL CLOUD WHICH
            COULD BE TOUCHING DOWN... BUT DUE TO THE DISTANCE WAS
            UNSURE.

&&

RPIERCE