First significant SW storm possible Thursday?

[weatherlover427]

ZONE FORECAST PRODUCT FOR EXTREME SOUTHWESTERN CALIFORNIA
NATIONAL WEATHER SERVICE SAN DIEGO CA
230 PM PST TUE DEC 9 2003

CAZ042-101130-
ORANGE COUNTY COASTAL AREAS-
230 PM PST TUE DEC 9 2003

.TONIGHT...CLEAR. AREAS OF LOW CLOUDS AND FOG LATE. LOWS 42 TO 50. LIGHT SOUTH WINDS.
.WEDNESDAY...MOSTLY CLOUDY WITH A 20 PERCENT CHANCE OF LIGHT RAIN OR DRIZZLE. HIGHS 60 TO 66. SOUTH WINDS 5 TO 10 MPH.
.WEDNESDAY NIGHT...MOSTLY CLOUDY WITH A 20 PERCENT CHANCE OF LIGHT RAIN. LOWS 47 TO 54. LIGHT SOUTHEAST WINDS.
.THURSDAY...CLOUDY WITH A 70 PERCENT CHANCE OF RAIN BY AFTERNOON. HIGHS 56 TO 63. SOUTH WINDS 10 MPH.
.THURSDAY NIGHT...A 70 PERCENT CHANCE OF RAIN. LOWS 45 TO 50. SOUTH WINDS AROUND 10 MPH...BECOMING NORTH 10 TO 15 MPH AFTER MIDNIGHT.
.FRIDAY...PARTLY CLOUDY. CHANCE OF SHOWERS IN THE MORNING. HIGHS 57 TO 63.
.FRIDAY NIGHT...PARTLY CLOUDY IN THE EVENING THEN CLEARING. LOWS 43 TO 48.
.SATURDAY...MOSTLY SUNNY. HIGHS 60 TO 66.
.SATURDAY NIGHT...MOSTLY CLEAR. LOWS 45 TO 50.
.SUNDAY...PARTLY CLOUDY. CHANCE OF RAIN IN THE AFTERNOON. HIGHS 63 TO 69.
.SUNDAY NIGHT...PARTLY CLOUDY. CHANCE OF RAIN. LOWS 46 TO 51.
.MONDAY...PARTLY CLOUDY. HIGHS 60 TO 67.
.MONDAY NIGHT...MOSTLY CLEAR. LOWS 44 TO 49.
.TUESDAY...MOSTLY SUNNY. HIGHS 62 TO 70.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN DIEGO CALIFORNIA
200 PM PST TUE DEC 9 2003

.SYNOPSIS...A TROUGH OF LOW PRESSURE OFF THE NORTHERN CALIFORNIA COAST WILL MOVE SOUTH TOMORROW. THIS SYSTEM WILL BRING INCREASING CLOUDS AND A SLIGHT CHANCE FOR LIGHT RAIN OR DRIZZLE DURING THE DAY. BETTER CHANCES FOR RAIN WILL BE ON THURSDAY AND THURSDAY NIGHT AS THE STORM MOVES ACROSS SOUTHERN CALIFORNIA. UP TO AN INCH OF RAIN IS EXPECTED IN THE MOUNTAINS WITH SNOW ABOVE 5500 FEET. SKIES WILL CLEAR DURING THE DAY FRIDAY AS HIGH PRESSURE BUILDS...WITH ANOTHER CHANCE OF RAIN LATE SUNDAY.

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

SKIES WERE CLEAR THIS AFTERNOON AND THE AIRMASS WAS VERY DRY WITH DEWPOINTS IN THE 20S AND 30S AT THE COAST AND IN THE SINGLE DIGITS AND TEENS IN THE MTNS. DEWPOINTS WILL RECOVER OVER THE NEXT 24 HOURS AS A SHORTWAVE NEAR SFO RACES ACROSS CENTRAL CALIFORNIA. THIS SYSTEM WILL BE TOO FAR NORTH TO BRING SIGNIFICANT CHANCES FOR RAIN TO SOCAL. HOWEVER...IT WILL TURN THE PRESSURE GRADIENTS MORE ONSHORE AND BRING MARINE LAYER MOISTURE BACK INTO COASTAL AREAS LATER TONIGHT...AND THE MARINE LAYER MAY DEEPEN ENOUGH TO PRODUCE SOME AREAS OF LIGHT RAIN OR DRIZZLE WEDNESDAY.

A SECOND SHORTWAVE WILL DIG SOUTH ALONG THE COAST WEDNESDAY NIGHT AND BRING A DECENT CHANCE AT SIGNIFICANT PRECIP THURSDAY AND THURSDAY NIGHT. THE OVERWATER TRAJECTORY IS FAVORABLE FOR MOISTURE TO WORK INTO THE SYSTEM WITH ONE THIRD TO ONE HALF INCH OF RAIN POSSIBLE WEST OF THE MOUNTAINS. OROGRAPHICS WILL PLAY A KEY ROLE IN RAIN AMOUNTS ON THE COASTAL MTNS SLOPES WHERE SOUTHWEST WINDS FROM 20 TO 30 KTS COULD GENERATE AN INCH OR MORE IN SOME AREAS. COLD AIR ALOFT WILL CREATE STEEP LAPSE RATES AND POSSIBLE THUNDERSTORMS AS 500 MB TEMPS FALL TO -26C THURSDAY AFTERNOON. SNOW LEVELS WILL LOWER TO AROUND 5000 FEET THURSDAY ABOVE WHICH SEVERAL INCHES OF SNOW IS LIKELY.

ON FRIDAY THE TROUGH SLOWLY MOVES EAST WITH RESIDUAL MOISTURE AND COLD AIR INSTABILITY PRODUCING A FEW LINGERING SHOWERS. CLEARING SKIES FRIDAY NIGHT AND SATURDAY BEFORE ANOTHER FAST MOVING UPPER TROUGH OVER THE PACIFIC BRINGS ANOTHER CHANCE FOR SHOWERS SUNDAY.