FXUS66 KMTR 231148
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
251 AM PST WED DEC 23 2009

.DISCUSSION...AS OF 2:51 AM PST WEDNESDAY...SATELLITE IMAGERY IS
SHOWING CLEAR SKIES ACROSS THE DISTRICT WITH SURFACE OBSERVATIONS
INDICATING A PERSISTENT NORTHERLY SURFACE PRESSURE GRADIENT,...
STILL 13 MB BETWEEN SFO AND LAS AND 5.8 MB FROM SFO TO SBA...AND
RESULTING NORTHERLY WINDS IN THE 5-15 MPH RANGE...WITH STRONGER GUSTS
OCCURRING OVER THE NORTH AND EAST BAY HILLS. SLIGHTLY WARMER DAYTIME
TEMPERATURES ARE EXPECTED TODAY AS HIGH PRESSURE ALOFT BEGINS TO
BUILD OVER THE STATE. EVEN SO...HIGHS SHOULD STILL BE A DEGREE OR TWO
BELOW SEASONAL NORMALS. A WARMING TREND IS INDICATED OVER THE NEXT
FEW DAYS AS THE UPPER RIDGE AXIS EDGES EASTWARD OVER THE STATE...AND
LOW-LEVEL MOISTURE WILL BEGIN TO INCREASE FOR NIGHT AND MORNING
VALLEY FOG FORMATION. THE FORECAST WILL CONTINUE TO BE DRY UNTIL THE
WEEKEND WHEN AN UPPER TROUGH APPROACHES THE COAST. DIFFERENCES
CONTINUE AMONGST THE MEDIUM RANGE MODEL SOLUTIONS REGARDING THE
EFFECTS OF THIS TROUGH ON THE DISTRICT. THE LATEST RUNS OF THE GFS
CONTINUE TO BRING A DRY VORT MAX ACROSS THE AREA WHICH WOULD RESULT
IN MINIMAL RAINFALL. MEANWHILE...THE ECMWF BRINGS A NEGATIVELY TILTED
COLD UPPER TROUGH TO THE WEST COAST ON SATURDAY WHICH WOULD SPREAD
RAIN CHANCES ACROSS MUCH OF THE DISTRICT SATURDAY AND SUNDAY WITH
CONTINUED UNSETTLED WEATHER INTO THE EARLY PART OF NEXT WEEK AS
ADDITIONAL IMPULSES MOVE THROUGH THE FLOW. HAVE MAINTAINED THE
PREVIOUS FORECAST FAVORING THIS WETTER ECMWF SOLUTION FOR RAIN
CHANCES BEGINNING ON SATURDAY.

&&

.AVIATION...AS OF 4:00 AM TUESDAY...DRY NORTHWESTERLY FLOW
WILL KEEP VFR CONDITIONS THROUGH WEDNESDAY.

VICINITY OF KSFO...VFR CONDITIONS THROUGH WEDNESDAY.

KSFO BRIDGE APPROACH...SAME AS KSFO.

MRY BAY AREA TERMINALS...VFR CONDITIONS THROUGH WEDNESDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
   .TDA..SCA...POINT ARENA TO POINT PIEDRAS BLANCAS 10-60 NM
               PIGEON POINT TO POINT PIEDRAS BLANCAS 0-10 NM.

$$

PUBLIC FORECAST: SSA
AVIATION/MARINE: W PI

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO