FXUS66 KMTR 241302
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
230 AM PST THU DEC 24 2009

.DISCUSSION...AS OF 2:30 AM PST THURSDAY...SATELLITE IMAGERY SHOWS A
FEW HIGH CLOUDS MOVING ACROSS THE DISTRICT...OTHERWISE MOSTLY CLEAR
SKIES AND COOL TEMPERATURES ARE THE PREVAILING CONDITIONS ACROSS THE
AREA. A FEW LOCATIONS ARE STARTING TO SEE PATCHY FOG...WITH
FREEZING FOG OCCURRING AT THE SANTA ROSA AIRPORT AS OF LAST
OBSERVATION TIME.

LITTLE CHANGE IS EXPECTED ACROSS THE DISTRICT FOR THE NEXT TWO DAYS
AS HIGH PRESSURE REMAINS OVER THE WEST. BY THE WEEKEND...THOUGH...
AN APPROACHING UPPER TROUGH IS PROGGED TO BRING SOME RAIN TO THE
AREA. THERE ARE STILL DIFFERENCES BETWEEN THE MODELS REGARDING THE
TIMING OF THIS SYSTEM...BUT FOR NOW IT APPEARS THE RAIN WILL SPREAD
ACROSS THE DISTRICT ON SATURDAY WITH ADDITIONAL SHOWERS MOVING
THROUGH ON SUNDAY AND MONDAY AS THE MAIN UPPER LOW MOVES TOWARDS
SOUTHERN CALIFORNIA. BOTH THE GFS AND THE ECMWF INDICATE A SPLITTING
OF THE FLOW BY EARLY NEXT WEEK WITH THE UPPER LOW MOVING ACROSS SOCAL
AND INTO SOUTHERN ARIZONA WHILE THE NORTHERN BRANCH OF THE TROUGH
MOVES ACROSS THE PACIFIC NORTHWEST. HAVE KEPT SHOWER CHANCES IN THE
FORECAST THROUGH THE EXTENDED PERIOD ALTHOUGH THERE ARE INDICATIONS
OF ANOTHER LARGE UPPER RIDGE BUILDING ALONG THE COAST ONCE AGAIN FOR
DRIER WEATHER.

&&

.AVIATION...AS OF 4:30 AM THURSDAY...OFFSHORE FLOW WILL KEEP VFR
CONDITIONS THROUGH CHRISTMAS DAY.

VICINITY OF KSFO...VFR CONDITIONS THROUGH CHRISTMAS DAY. WINDS WILL
BE EAST TO NORTHEAST 5-10 KT THROUGH MID TO LATE AFTERNOON.

KSFO BRIDGE APPROACH...SAME AS KSFO.

MRY BAY AREA TERMINALS...VFR CONDITIONS THROUGH CHRISTMAS DAY.
LIGHT EASTERLY WINDS WILL SWITCH TO WESTERLY LATE IN THE AFTERNOON.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
   .TDA...NONE

$$

PUBLIC FORECAST: SSA
AVIATION/MARINE: W PI

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO