AREA FORECAST DISCUSSION

 
 FXUS66 KMTR 250541
 AFDMTR
 
 AREA FORECAST DISCUSSION
 NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
 940 PM PST TUE NOV 24 2009
 
 .DISCUSSION...AS OF 8:40 PM PST TUESDAY...A RIDGE OF HIGH PRESSURE
 ALOFT ALONG WITH A DRY OFFSHORE FLOW PUSHED TEMPERATURES 5 TO 10
 DEGREES ABOVE NORMAL TODAY. HIGHS GENERALLY RANGED FROM THE MID 60S
 TO LOWER 70S...WITH SOME MID 70S ACROSS MONTEREY AND SAN BENITO
 COUNTIES. EXCEPT FOR SOME PATCHY EARLY MORNING FOG IN THE NORTH BAY
 VALLEYS...SKIES WERE CRYSTAL CLEAR ACROSS OUR ENTIRE AREA THROUGH THE
 DAY AND VISIBILITIES WERE EXCELLENT. MORE OF THE SAME IS EXPECTED ON
 WEDNESDAY.
 
 A PIECE OF ENERGY IS FORECAST TO BREAK OFF FROM THE GULF OF ALASKA
 TROUGH AND MOVE INLAND OVER THE PAC NW AND FAR NORTHERN CALIFORNIA ON
 THURSDAY NIGHT. HIGH CLOUDS IN ADVANCE OF THIS APPROACHING SYSTEM
 WILL BEGIN TO OVERSPREAD OUR AREA ON THANKSGIVING DAY...BUT PRECIP IS
 EXPECTED TO REMAIN OFFSHORE UNTIL AFTER SUNSET. INCREASING HIGH
 CLOUDS AND A REVERSAL IN THE FLOW FROM LIGHT OFFSHORE TO LIGHT
 ONSHORE WILL MEAN TEMPERATURES WILL DROP BACK TO AROUND NORMAL ON
 THANKSGIVING. THE MOST RECENT OUTPUT FROM THE NAM...GFS...AND ECMWF
 ALL INDICATE THAT ONLY THE NORTH BAY WILL SEE ANY PRECIP ON THURSDAY
 NIGHT...AND ANY RAIN THAT DOES FALL WILL BE VERY LIGHT. DRY WEATHER
 WILL RETURN IN ALL AREAS BY FRIDAY AS A BRISK AND COOL NORTHWEST FLOW
 DEVELOPS. A WARMING TREND IS THEN EXPECTED DURING THE HOLIDAY WEEKEND
 AS A RIDGE BUILDS IN OFF THE EASTERN PACIFIC.
 
 THE GFS IS INDICATING THAT THE WESTERLIES MAY UNDERCUT THE RIDGE
 DURING THE SECOND HALF OF NEXT WEEK. SUCH A PATTERN CHANGE AND THE
 POTENTIAL FOR WET WEATHER IN NORTHERN AND CENTRAL CALIFORNIA IN
 EARLY DECEMBER IS SUPPORTED BY THE PRESENCE OF A PROGRESSIVE MJO IN
 THE WESTERN PACIFIC. HOWEVER...THERE REMAINS A LOT OF UNCERTAINTY AT
 THIS POINT DUE TO THE FACT THAT THE MJO IS RATHER WEAK...THIS
 CHANGE IS STILL AT LEAST 8-10 DAYS AWAY...AND THE ECMWF HAS NOT YET
 SHOWN ANY SIGNS OF TRENDING WET LIKE THE GFS.
 
 &&
 
 .AVIATION...AS OF 9:40 PM PST TUESDAY...CLEAR SKIES WILL PERSIST
 THROUGH WEDNESDAY UNDER THE INFLUENCE OF HIGH PRESSURE. PATCHY FOG
 IS POSSIBLE ONCE AGAIN IN THE VALLEYS OVERNIGHT.
 
 ALL TERMINALS(EXCEPT KSTS)...VFR CONDITIONS EXPECTED THROUGH
 WEDNESDAY WITH LIGHT WINDS.
 
 &&
 
 
 .MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...NONE.
 
 
 $$
 
 PUBLIC FORECAST: DYKEMA
 AVIATION/MARINE: CW
 
 NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO