000 FXUS66 KMTR 251213 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA 319 AM PST WED NOV 25 2009 .DISCUSSION...AS OF 3:15 AM WEDNESDAY...SLIGHT CHANCE FOR PRECIP LATE THURSDAY AND EARLY FRIDAY FOLLOWED BY SEASONABLE WEATHER. A RIDGE OF HIGH PRESSURE COMBINED WITH LIGHT NORTHERLY OFFSHORE FLOW CONTINUES TO PRODUCE GENERALLY DRY CONDITIONS ACROSS THE BAY AREA. THE OVERNIGHT FOG PRODUCT SHOWS NO STRATUS IMPACTING THE COASTLINE... BUT SOME PATCHY FOG IS NOTED IN THE NORTH BAY. RECENT OBS INDICATE PATCHY FOG IN SONOMA AND NAPA VALLEYS WITH VISIBILITIES LESS THAN 1 MILE AT TIMES. ELSEWHERE...DEW POINT DEPRESSIONS ARE DECENT WITH CLEAR SKIES DOMINATING. ONE OTHER ITEM OF NOTE...IS ANOTHER NIGHT OF MILD CONDITIONS IN THE HIGHER TERRAIN. CURRENT READINGS ARE A LITTLE COOLER THAN LAST NIGHT...BUT TEMPS IN THE UPPER 50S TO LOWER 60S IS MILD FOR THE HILLS IN NOVEMBER. CURRENT LONGWAVE PATTERN HAS A RIDGE OF HIGH PRESSURE OVERHEAD AND OVER MUCH OF THE WEST COAST. FARTHER UPSTREAM A LOW PRESSURE SYSTEM AND ASSOCIATED COLD FRONT CONTINUES TO SWING THROUGH THE GULF OF AK AND A SECOND DEEPENING SHORTWAVE TROUGH IS NEAR 150W. SHORT TERM(TODAY-FRIDAY)... LITTLE CHANGE IS FORECAST IN THE OVERALL PATTERN TODAY FROM YESTERDAY. AS MENTIONED ABOVE...SOME PATCHY FOG WILL BE POSSIBLE THROUGH THE EARLY MORNING HOURS IN THE NORTH BAY. OTHERWISE... EXPECT ANOTHER DAY OF WALL TO WALL SUNSHINE. LATER TODAY THE RIDGE WILL WEAKEN AND SLIDE TOWARD THE SOUTHEAST. AS THIS HAPPENS... THE SECOND UPSTREAM FEATURE WILL DEEPEN AND MOVE TOWARD THE COAST THURSDAY. MODELS ARE IN DECENT AGREEMENT WITH THE TIMING OF THIS FEATURE. AS MENTIONED IN PREVIOUS DISCUSSIONS...THANKSGIVING DAY STILL LOOKS TO START OF MOSTLY SUNNY BUT AS THE SHORTWAVE TROUGH AND ASSOCIATED FRONT MOVE CLOSER THROUGH THE DAY CLOUDS WILL STEADILY INCREASE. ALL MODEL GUIDANCE KEEPS ANY PRECIP WELL OFFSHORE THROUGH 4 PM ON THANKSGIVING. AFTER 4 PM THE LIKELIHOOD FOR DEVELOPING LIGHT SHOWERS WILL INCREASE. MODEL GUIDANCE HAS BEEN PRETTY PERSISTENT WITH KEEPING THE BULK OF THE PRECIP SAN FRANCISCO BAY NORTHWARD. THE 00Z MODELS ARE NO DIFFERENT AND FORECAST WILL REFLECT THIS. EVEN WITH THE ADVERTISED RAINFALL THURSDAY NIGHT INTO EARLY FRIDAY AMOUNTS WILL BE LIGHT...GENERALLY A FEW HUNDREDTHS TO A TENTH OR TWO. WILL CONTINUE TO KEEP MUCH OF THE SOUTHERN CWA DRY WITH ONLY CLOUDS MENTIONED. THE COLD FRONT WILL EXIT THE CWA ON FRIDAY WITH A CLEARING TO FOLLOW. A DROP IN TEMPERATURE IS EXPECTED ON FRIDAY AS 850 MB TEMPS DROP A FEW DEGREES AND COOL NORTHWEST FLOW DEVELOPS AT THE SFC. LONG TERM(SATURDAY-TUESDAY)... LITTLE CHANGE WAS MADE TO THE LONG TERM FORECAST. HIGH PRESSURE IS FORECAST TO BUILD BEHIND THE DEPARTING COLD FRONT WITH A SLIGHT WARMING TREND. ANOTHER SYSTEM IS FORECAST TO SWING THROUGH NW PAC EARLY NEXT WEEK...BUT WITH LITTLE AFFECT ON THE CWA. && .AVIATION...AS OF 4:10 AM PST WEDNESDAY...HIGH PRESSURE OVER THE GREAT BASIN WILL KEEP A DRY OFFSHORE FLOW OVER THE AREA. HOWEVER SOME PATCHY GROUND FOG CAN BE EXPECTED AROUND STS EARLY THIS MORNING. ALL TERMINALS(EXCEPT KSTS)...VFR CONDITIONS EXPECTED THROUGH WEDNESDAY WITH LIGHT WINDS. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. $$ PUBLIC FORECAST: MM AVIATION/MARINE: CW/W PI NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO