FXUS66 KMTR 061651 AAA
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
850 AM PST SUN DEC 6 2009

.DISCUSSION...AS OF 8:50 AM PST SUNDAY...COLD AIRMASS IS ALREADY
FILTERING INTO THE STATE WITH CURRENT READINGS IN THE 30S TO LOWER
40S ACROSS THE DISTRICT. AN UPPER LOW CURRENTLY OVER WESTERN OREGON
WILL CONTINUE TO PUSH SOUTHWARD WITH REINFORCING COLD CP AIRMASS
BEHIND IT. SHOWERS ARE POSSIBLE ACROSS THE DISTRICT BEGINNING
TONIGHT AND CONTINUING THROUGH MONDAY WITH LOW SNOW LEVELS...AS LOW
AS 500 FEET IN THE NORTH BAY AND AROUND 1500 FEET ACROSS THE
SOUTHERN PARTS OF THE CWA. QPF WITH THIS SYSTEM IS NOT TOO HIGH FOR
OUR AREA WITH AROUND A HALF INCH IN THE WETTEST LOCATIONS. SNOW
ACCUMULATIONS...IN THE HILLS...ARE EXPECTED TO BE SMALL.

CLEARING SKIES AFTER THE DEPARTURE OF THIS SYSTEM LATE MONDAY WILL
SET THE STAGE FOR COLD OVERNIGHT TEMPERATURES TUESDAY MORNING.
FREEZE WATCH REMAINS IN EFFECT FOR THAT TIME PERIOD FOR INLAND
VALLEYS AND NORTH BAY MOUNTAINS.

MODELS NOW INDICATE MOSTLY DRY CONDITIONS FROM TUESDAY UNTIL EARLY
THURSDAY WHEN A MOISTENING ZONAL FLOW IS PROGGED TO BEGIN TO IMPACT
THE CENTRAL COAST. LATEST GFS BRINGS MODERATELY HEAVY PRECIP TO THE
AREA BY NEXT SATURDAY...ALTHOUGH THERE AREA STILL VAST DIFFERENCES
AMONGST THE MODEL OUTPUT REGARDING TIMING...BOTH RUN-TO-RUN AND
BETWEEN THE DIFFERENT MEDIUM RANGE MODELS.

&&

.AVIATION...UPDATE...AS OF 5:15 AM PST SUNDAY...LOW/MID-LEVEL
CLOUDS HAVE FORMED OFF THE COAST AND OVER NEAR-COAST TERMINALS
WITHIN THE LAST 1-2 HOURS. CURRENT THINKING IS THAT THE CIGS
WILL BE 1500-2000FT INITIALLY...THEN LIFT TO 2500-3500 FT DURING THE
LATE MORNING HOURS. EXACT TIMING OF THIS WILL BE VERY DIFFICULT...
HOWEVER WILL LEAN TOWARDS A MORE PESSIMISTIC OUTLOOK DUE TO WIDE
SPATIAL EXTENT OF THESE CLOUDS ON SATELLITE FOG PRODUCT. MID/HIGH-
LEVEL CLOUDS WILL CONTINUE TO FILTER IN LATER TODAY WITH GUSTY
AFTERNOON WESTERLY WINDS. AS EVEN MORE COOLER AIR SLIDES IN
TONIGHT...PRECIPITATION CHANCES WILL ALSO INCREASE. FOR MOST AREAS
THE RAIN WILL NOT BEGIN UNTIL AFTER MIDNIGHT. HAVE MENTIONED THE
POSSIBILITY FOR -RASN FOR THE KSTS TAF DUE TO THE COLD TEMPERATURES
THAT ARE EXPECTED TO BE IN PLACE. ELSEWHERE...THE RAIN SHOULD LAST
INTO MONDAY AFTERNOON WITH GENERALLY SSW WINDS.

VICINITY OF KSFO...MVFR CIGS AND VFR VSBYS DEVELOPED OFF THE COAST
AND PUSHED INLAND THIS MORNING. CLD BASES 1500-2000 FT...EXPECTED
TO LIFT DURING THE MID-LATE MORNING HOURS. ADDITIONAL MID/HIGH-LEVEL
CLOUDS AND ASSOCIATED RAIN MOVING IN LATE TONIGHT AFTER MIDNIGHT.
PERIODS OF MOD-HVY RAIN POSSIBLE INTO MONDAY MORNING.

KSFO BRIDGE APPROACH...SAME AS KSFO.

MRY BAY AREA TERMINALS...CLEAR SKIES CURRENTLY...HOWEVER THERE
IS A SLIGHT CHANCE OF STRATUS/FOG FORMATION AROUND KMRY OR KSNS THIS
MORNING. STRATUS HAS DEVELOPED ALONG THE COAST AND WILL POSSIBLY MOVE
OVER MRY BAY TERMINALS THIS MORNING. CLOUDS WILL MOST LIKELY STAY IN
TODAY...BUT CIGS SHOULD LIFT ABOVE 2500 FT IN THE LATE MORNING AND
EARLY AFTERNOON HOURS. OTHERWISE MID/HIGH-LEVEL CLOUDS MOVING IN
ASSOCIATED WITH APPROACHING LOW PRESSURE...AND EVENTUALLY RAIN
SHOWERS DEVELOPING LATE TONIGHT LASTING INTO MONDAY. PERIODS OF MOD-
HVY RAIN POSSIBLE INTO MONDAY MORNING.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
    .LATE MON NIGHT-TUE MORNING...FREEZE WATCH FOR VALLEY ZONES
                                  AND N BAY MOUNTAINS.

$$

PUBLIC FORECAST: SSA
AVIATION/MARINE: TENTINGER

NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO