502
FXUS66 KMTR 220614
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA CA
905 PM PST SAT NOV 21 2009
DISCUSSION...AS OF 9:05 PM PST SATURDAY
SATURDAY WAS A SUNNY BUT
COOL DAY ACROSS THE REGION. HIGH TEMPERATURES WERE GENERALLY IN THE
MID TO UPPER 50S...AND WERE ON AVERAGE ABOUT FIVE DEGREES BELOW
NORMAL. SOME MID AND HIGH LEVEL CLOUDS HAVE BEGUN TO OVERSPREAD THE
NORTHERN PORTION OF OUR REGION THIS EVENING. THESE CLOUDS ARE
ASSOCIATED WITH A WEATHER SYSTEM APPROACHING THE COAST OF THE PAC NW
AND FAR NORTHERN CA AT THE PRESENT TIME. CLOUDS WILL LOWER AND
THICKEN ACROSS THE NORTH BAY OVERNIGHT AND...ACCORDING TO BOTH THE
00Z NAM AND 00Z GFS...LIGHT RAIN WILL DEVELOP ACROSS THE NORTHERN
HALF OF THE NORTH BAY COUNTIES SOMETIME AFTER MIDNIGHT TONIGHT.
THESE TWO MODELS THEN SLIDE LIGHT PRECIP A BIT FATHER SOUTH ON
SUNDAY MORNING...AND MEASURABLE RAIN MAY MAKE IT AS FAR SOUTH AS SAN
FRANCISCO BY MID MORNING SUNDAY...BUT PROBABLY NO FATHER SOUTH. A
FORECAST UPDATE WAS COMPLETED EARLIER THIS EVENING TO ADJUST THE
POP AND WEATHER GRIDS TO BRING THEM MORE IN LINE WITH LATEST MODEL
GUIDANCE. CURRENT SATELLITE AND REGIONAL RADAR DATA INDICATE
THAT MODELS HAVE A REASONABLY GOOD HANDLE ON THE SHORT TERM FORECAST.
SKIES SHOULD CLEAR ACROSS THE REGION ON SUNDAY AFTERNOON AS THE
SYSTEM MOVES QUICKLY OFF TO THE EAST. AN UPPER LEVEL RIDGE IS THEN
FORECAST TO GRADUALLY BUILD OVER CA THROUGH MIDWEEK...PRODUCING
DRY WEATHER THROUGH WEDNESDAY AND PROBABLY THROUGH THANKSGIVING DAY
AS WELL. DAYTIME TEMPERATURES ARE FORECAST TO BE ABOVE NORMAL
THROUGH MOST OF THE WEEK. THE ECMWF CONTINUES TO INDICATE THAT A WEAK
SYSTEM WILL MOVE INLAND TO OUR NORTH LATE ON THANKSGIVING DAY...WITH
THE TAIL END OF A COLD FRONT POSSIBLY CLIPPING THE NORTH BAY WITH
LIGHT PRECIP BY THAT EVENING. THE GFS HAS CONSISTENTLY BEEN SLOWER
WITH THAT SYSTEM THAN THE EUROPEAN. THE UPSHOT IS THAT IF PRECIP DOES
OCCUR ON THANKSGIVING...IT WILL OCCUR LATE IN THE DAY AND PROBABLY
ONLY ACROSS THE FAR NORTHERN PART OF OUR FORECAST AREA.
AVIATION...AS OF 10:00 PM PST SATURDAY
THE TAIL END OF A
FRONTAL SYSTEM WILL BRING SOME LOWER AND MID LEVEL CLOUDS INTO THE
SFO BAY AREA LATER TONIGHT. BASES COULD GET DOWN TO 2500-3000 FEET
AFTER 12Z. SCT-BKN AFTERNOON CUMULUS CLOUDS EXPECTED IN THE
AFTERNOON. LOW CLOUDS NOT EXPECTED TO REACH THE MRY BAY AREA. WINDS
WILL BE LIGHT SOUTHERLY SUNDAY MORNING SWITCHING TO WEST IN THE
AFTERNOON.
VICINITY OF KSFO...CEILINGS AT 2500-3000 FEET COULD AFFECT THE
AIRPORT AFTER 12Z. LIGHT SOUTH TO SOUTHEAST WINDS 5 KT OR LESS
EXPECTED DURING THE MORNING HOURS SWITCHING TO W TO 15 KT IN THE
AFTERNOON.
KSFO BRIDGE APPROACH...SAME AS KSFO.
MONTEREY BAY TERMINALS...VFR CONDITIONS THROUGH SUNDAY.
MTR WATCHES/WARNINGS/ADVISORIES
.TNGT...SCA...PT PINOS TO PT PIEDRAS BLANCAS TO 10 NM
SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10 TO 60 NM
PUBLIC FORECAST: DYKEMA
AVIATION/MARINE: W PI
NWS ON THE WEB AT WEATHER.GOV/SANFRANCISCO
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