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Forecast Discussion:Central California
930 AM PST SAT NOV 21 2009
DISCUSSION
AS OF 8:45 AM PST SATURDAY...THE FIRST VISIBLE SATELLITE IMAGE OF THE DAY IS SHOWING MOSTLY CLEAR SKIES ACROSS THE AREA THIS MORNING. OVER NIGHT LOWS WERE PRETTY CHILLY LAST NIGHT BEHIND THE DEPARTING COLD FRONT. THE CHILLIEST AREA WAS OF COURSE THE NORTH BAY VALLEYS WITH LOWS IN THE LOW TO MID 30S. SONOMA COUNTY AIRPORT MADE IT TO 32 DEGREES AND WAS REPORTING FREEZING FOG THIS MORNING. MEANWHILE NAPA AIRPORT MADE IT DOWN TO 36 DEGREES AND ALSO REPORTED A BRIEF PERIOD OF FREEZING FOG. TONIGHT WILL NOT BE QUITE AS CHILLY IN THE NORTH BAY VALLEYS WITH SOME MID AND UPPER LEVEL CLOUDS EXPECTED TO MOVE IN THIS EVENING. THESE CLOUDS WILL FORM IN RESPONSE TO A COLD FRONT BRUSHING BY THE AREA OVERNIGHT. THIS FRONT WILL ALSO BRING A SLIGHT CHANCE OF PRECIPITATION TO NAPA AND SONOMA COUNTIES. THE FORECAST CONTINUES TO DRY OUT TOMORROW AS A RIDGE OF HIGH PRESSURE BUILDS OVER THE EASTERN PACIFIC. TEMPERATURES ARE EXPECTED TO WARM UP A BIT THIS WEEK WITH THE RIDGE OF HIGH PRESSURE PUSHING 500 MB HEIGHTS TO 578 DM MONDAY AFTERNOON. THIS WILL RESULT IN TEMPERATURES WARMING TO MID 60S MONDAY AND POSSIBLY THE LOW 70S BY TUESDAY. THE WARMEST TEMPERATURES WILL MOST LIKELY BE IN THE SOUTHERN SALINAS VALLEY WITH KING CITY REACHING 72 DEGREES BY MID WEEK. THANKSGIVING DAY LOOKS TO BE MOSTLY DRY AND PLEASANT. HOWEVER...THE 0000 UTC ECMWF AND 1200 UTC GFS MODELS DO BEGIN TO DIVERGE ON THEIR SOLUTIONS BY THURSDAY. THE ECMWF INSISTS ON DROOPING A TROUGH OF LOW PRESSURE ACROSS NORTHERN CALIFORNIA RESULTING IN A SLIGHT CHANCE OF PRECIPITATION FOR THE NORTH BAY AREA. MEANWHILE THE OPERATIONAL GFS IS SLOWER WITH THIS FEATURE AND APPEARS TO LIFT THE TROUGH NORTHWARD INTO BC SPARING THE AREA OF PRECIPITATION THANKSGIVING DAY AND INTO THE HOLIDAY WEEKEND. &&
AVIATION
AS OF 9:30 AM PST SATURDAY...CLEAR SKIES ARE EXPECTED TODAY WITH ONLY HIGH CLOUDS MOVING ACROSS LATER TODAY. THE SOUTHERN EDGE OF A WEAK FRONT WILL BRING AN INCREASE IN CLOUDS TO THE NORTH BAY ALONG WITH A CHANCE OF SHOWERS OVERNIGHT. VICINITY OF KSFO...VFR CONDITIONS THROUGH TODAY. WEST WINDS AOB 10 KT EXPECTED THIS AFTERNOON. KSFO BRIDGE APPROACH...VFR. MONTEREY BAY TERMINALS...VFR CONDITIONS TODAY AND TONIGHT. LIGHT WEST WINDS EXPECTED. &&
MTR WATCHES/WARNINGS/ADVISORIES
.TDA...SCA FOR HAZ SEAS PT ARENA TO PIGEON PT 10-60 NM UNTIL 2 PM ...SCA PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM ...SCA PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM ...SCA STARTING 1 PM PIGEON PT TO PT PINOS 0-10 NM ...SCA FOR ROUGH BAR CONDITIONS UNTIL 2 PM $$ PUBLIC FORECAST: LARRY AVIATION/MARINE: SSA NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO