Snow Advisory 4, NWS San Diego, CA

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CA
120 PM PST SAT DEC 16 2006

.SYNOPSIS...A STORM SYSTEM APPROACHING FROM THE NORTHWEST WILL BRING
VERY COOL AND BREEZY WEATHER THIS WEEKEND. RAIN WILL OCCUR AT TIMES
AT LOWER ELEVATIONS WITH SNOW IN THE MOUNTAINS AND EVEN INTO THE
HIGH DESERTS. MOST OF THE RAIN IS EXPECTED TO FALL THIS EVENING...
ALTHOUGH SOME SHOWERS WILL OCCUR ANYTIME THROUGH SUNDAY NIGHT.
BEHIND THIS SYSTEM...STRONG GUSTY WINDS WILL DEVELOP THROUGH AND
BELOW PASSES AND CANYONS MONDAY THROUGH TUESDAY...BUT IT WILL REMAIN
QUITE CHILLY UNTIL MID WEEK.

&&

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

SKIES WERE CLOUDY TODAY AND WE HAD A FEW LIGHT SHOWERS WEST OF THE
MOUNTAINS AS MOIST ONSHORE FLOW INCREASED IN THE LOWER LAYERS OF THE
ATMOSPHERE. ALERT GAGES NOW SHOW RAIN IS ACCUMULATING ON THE COASTAL
SLOPES. THE VISIBLE SATELLITE IMAGERY SHOWED A BROKEN BAND OF LOW
CLOUDS STRETCHING STRETCHING FROM NEAR POINT CONCEPTION...OFFSHORE
TO ABOUT 180 MILES WEST OF SAN DIEGO. THE IR ENHANCEMENT IS
UNIMPRESSIVE...BUT IT IS FAIRLY WELL DEFINED IN THE VISIBLE IMAGERY
AND MOVING RAPIDLY EAST. A FEW WIND GUSTS TO 35 MPH HAVE BEEN
REPORTED FROM THE HIGH DESERTS AND MOUNTAINS. ONSHORE SURFACE
PRESSURE GRADIENTS ARE INCREASING.

THE 12Z MODEL RUNS OF THE WRF/GFS/UK MODELS ALL POINT TO A CUT-OFF
LOW DEVELOPING OVER THE LOWER COLORADO RIVER VALLEY ON MONDAY. UNTIL
THEN...SOME PRECIPITATION WILL FALL AND THE WINDS WILL BLOW...BUT
THE STORM SYSTEM DOES NOT HAVE A GOOD MOISTURE SUPPLY SO STORM TOTAL
PRECIPITATION SHOULD REMAIN SOMEWHAT MODEST. BASED ON THE LATEST
MODEL GUIDANCE...THE FRONT MOVING THROUGH EARLY THIS EVENING IS
THERMALLY CHALLENGED WITH NO GOOD VERTICAL STRUCTURE...AND WILL NOT
HAVE MUCH SUPPORT ALOFT. IT WILL BE QUITE COLD THOUGH...SO SNOW
LEVELS WILL FALL BELOW 4000 FEET TONIGHT...AND IT WILL NOT BE OUT OF
THE QUESTION TO SEE SEVERAL INCHES OF SNOW ABOVE 5K FT IN SOME
AREAS... WITH A DUSTING POSSIBLE IN THE HIGH DESERTS BY TUE MORNING.
THE COLD AIR ALOFT COULD TRIGGER THUNDERSTORMS AS WELL...BUT IT WILL
LIKELY TAKE SOME DAYTIME HEATING TO GET THEM GOING SINCE JET AND
FRONTAL DYNAMICS ARE WEAK. COLD AIR ALOFT AND A SECONDARY FEATURE
ROTATING AROUND THE UPPER TROUGH WILL MOVE THROUGH SUN AND SUN
EVENING. THIS WILL KEEP A CHANCE OF CONVECTIVE SHOWERS INTO SUN
NIGHT BEFORE THE UPPER FLOW TURNS MORE NORTHERLY.

SINCE THE MODELS ALL INDICATE A CUT-OFF UPPER LOW WILL FORM CLOSE
BY...SOME PRECIPITATION WILL REMAIN IN THE FORECAST...EVEN THOUGH
MOISTURE IS MARGINAL AND OFFSHORE SURFACE PRESSURE GRADIENTS
DEVELOP. THE BEST CHANCE FOR ANY FURTHER SIGNIFICANT PRECIPITATION
AFTER SUNDAY EVENING WILL BE IN THE MOUNTAINS AND HIGH DESERTS WHERE
UPSLOPE FLOW WILL BE THE DRIVING FORCE. MOISTURE AGAIN IS
QUESTIONABLE...BUT THE MODEL CROSS SECTIONS ALL SHOW ENOUGH TO KEEP
SKIES MOSTLY CLOUDY THERE. IT WILL BE QUITE COLD AS WELL...SO IF
PRECIPITATION IS SQUEEZED OUT...MUCH OF IT WOULD FALL AS SNOW.

IN TERMS OF WIND...SOME GUSTS OVER 50 MPH STILL LOOK POSSIBLE IN THE
MOUNTAINS AND DESERTS AS THE WEAK FRONT GETS CLOSER...SO THE WIND
ADVISORY WILL CONTINUE. AFTER SUN...THE TREND IS INCREASINGLY
OFFSHORE...WITH SOME GOOD SUPPORT BEING GENERATED ON THE BACK SIDE
OF THE CUT-OFF LOW. ONCE AGAIN... WIND ADVISORIES MAY BE NEEDED...
BUT CURRENT GUIDANCE DOES NOT SUPPORT HIGH WIND CRITERIA...PERHAPS
DUE TO THE LACK OF A GOOD THERMAL GRADIENT.

THE WEATHER IS LOOKING MIGHTY FINE BY MIDWEEK AND BEYOND AS THE
UPPER LOW WORKS FARTHER EAST AND A WEAK HIGH PRESSURE RIDGE BUILDS
IN FROM THE PACIFIC. LOOK FOR WARMER WEATHER WITH LIGHTER WINDS AND
FAIR SKIES INTO FRI. THE MODELS ARE HINTING AT STRONGER OFFSHORE
AGAIN BY NEXT WEEKEND.

&&

.AVIATION...
MULTILEVEL CLOUDS AHEAD OF COLD FRONT AS IT APPROACHES THE SOUTHERN
CALIFORNIA COAST. BASES OF CLOUD LAYER GENERALLY BETWEEN 2000 AND
3000 FEET WITH AREAS OF MVFR VIS IN LIGHT RAIN OR DRIZZLE. COLD
FRONT EXPECTED TO MAKE LANDFALL ABOUT 00Z-02Z IN ORANGE COUNTY AND A
COUPLE OF HOURS LATER IN SAN DIEGO COUNTY...SPREADING INLAND OVER
NIGHT. HEAVIEST RAIN EXPECTED TONIGHT. THUNDERSTORMS POSSIBLE
TONIGHT THROUGH SUNDAY. BASES AND VIS EXPECTED TO LOWER TO IFR
CONDITIONS IN HEAVY RAIN AND FOG TONIGHT. WINDS AT 5K FT...WEST
20-25 KT...THEN SOUTHWEST TO WEST 25-30 KT TONIGHT...DROPPING TO
10-15 KT SUN MORNING. WINDS AT 10K FT...SOUTHWEST TO WEST 35-45
KT...BECOMING 40-50 KT TONIGHT...DROPPING TO 15-25 KT SUN MORNING.

&&

.MARINE...
A LARGE NW SWELL WITH 14 SEC PERIOD WILL INCREASE THROUGH SUNDAY
THEN DECREASE RAPIDLY MONDAY. A STRONG COLD FRONT WILL MOVE INTO THE
COASTAL WATERS LATE THIS AFTERNOON OR EVENING. THUNDERSTORMS
POSSIBLE TONIGHT THROUGH SUNDAY ALONG WITH WATERSPOUTS. WINDS WILL
INCREASE THROUGH TONIGHT AS THE TROUGH DEEPENS OVER THE AREA AND THE
COLD FRONT MOVES THROUGH. THIS WILL GENERATE HAZARDOUS SEAS AND VERY
ROUGH CONDITIONS THROUGH THE WEEKEND.

&&

.SGX WATCHES/WARNINGS/ADVISORIES...

COLD PACIFIC STORM TO AFFECT SOUTHWESTERN CALIFORNIA OVER THE
WEEKEND...SEE LAXSPSSGX.

WIND ADVISORY...SEE LAXNPWSGX.

HIGH SURF ADVISORY...SEE LAXCFWSGX.

SMALL CRAFT ADVISORY...SEE LAXCWFSGX.

&&

PUBLIC...JAD
AVIATION/MARINE...ECC

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN DIEGO CA
400 PM PST SAT DEC 16 2006

CAZ042-043-048-050-055-056-057-058-060-061-062-171200-
ORANGE COUNTY COASTAL AREAS-
SAN DIEGO COUNTY COASTAL AREAS-
SAN BERNARDINO AND RIVERSIDE COUNTY VALLEYS-THE INLAND EMPIRE-
SAN DIEGO COUNTY VALLEYS-
SAN BERNARDINO COUNTY MOUNTAINS-
RIVERSIDE COUNTY MOUNTAINS-
SANTA ANA MOUNTAINS AND FOOTHILLS-
SAN DIEGO COUNTY MOUNTAINS-
APPLE AND LUCERNE VALLEYS-
COACHELLA VALLEY-
SAN DIEGO COUNTY DESERTS-
400 PM PST SAT DEC 16 2006

THIS HAZARDOUS WEATHER OUTLOOK IS FOR ALL OF EXTREME SOUTHWESTERN
CALIFORNIA.

A COLD PACIFIC STORM WILL BRING RAIN AND MOUNTAIN SNOW WITH THE
HEAVIEST PRECIPITATION EXPECTED THIS EVENING. SOME LOCALLY HEAVIER
SHOWERS MAY DEVELOP THIS EVENING. ISOLATED THUNDERSTORMS COULD BRING
WATERSPOUTS OFF THE COAST. SHOWERS COULD LINGER SUNDAY INTO SUNDAY
NIGHT. DRIER...COLD OFFSHORE FLOW IS EXPECTED EARLY NEXT WEEK.

.DAY ONE... THROUGH TONIGHT.

SPECIAL WEATHER STATEMENT...SEE LAXSPSSGX. SOME LOCALLY HEAVIER
SHOWERS MAY DEVELOP THIS EVENING...AND LOCAL FLOODING OR DEBRIS
FLOWS WILL BE POSSIBLE IN AND NEAR RECENT BURN AREAS SUCH AS THE
ESPERANZA NEAR BEAUMONT AND SAN JACINTO. IN THE MOUNTAINS...SNOW
ACCUMULATIONS OF SEVERAL INCHES ARE POSSIBLE AND SNOW LEVELS WILL
DROP TO 3000 TO 4000 FEET LATE TONIGHT AND EARLY SUNDAY MORNING.

WIND ADVISORY FOR THE MOUNTAINS AND DESERTS UNTIL 9 PM TONIGHT...
SEE LAXNPWSGX.

HIGH SURF ADVISORY AND HIGH RIP CURRENT RISK FOR THE SAN DIEGO AND
ORANGE COUNTY COASTAL AREAS...SEE LAXCFWSGX AND LAXSRFSGX.

MARINE WEATHER STATEMENT...SEE LAXMWSSGX.

.DAYS TWO THROUGH SEVEN... SUNDAY THROUGH FRIDAY.

HIGH SURF ADVISORY AND HIGH RIP CURRENT RISK FOR THE SAN DIEGO AND
ORANGE COUNTY COASTAL AREAS THROUGH MONDAY MORNING...SEE LAXCFWSGX
AND LAXSRFSGX.

SCATTERED SHOWERS WILL LINGER SUNDAY INTO SUNDAY NIGHT...AND
PRECIPITATION COULD BE LOCALLY AND BRIEFLY HEAVY. THE SHOWERY
NATURE OF THE RAINFALL WILL RESULT IN HIGHLY VARIABLE AMOUNTS.

MODERATE TO LOCALLY STRONG NORTHEAST WINDS ARE POSSIBLE MONDAY AND
TUESDAY...MAINLY THROUGH AND BELOW THE MOUNTAIN PASSES AND CANYONS.

.SPOTTER INFORMATION STATEMENT...
SKYWARN WEATHER SPOTTER ACTIVATION IS NOT REQUESTED FOR THIS AREA...
HOWEVER WEATHER SPOTTERS ARE ENCOURAGED TO REPORT SIGNIFICANT WEATHER
CONDITIONS.

LAVIS