Area Forecast Discussion
Issued by NWS San Francisco Bay Area, CA

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000
FXUS66 KMTR 230137
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
537 PM PST SAT NOV 22 2014

.SYNOPSIS...DRY WEATHER CONDITIONS AND UNSEASONABLY MILD
TEMPERATURES ARE EXPECTED THROUGH MIDWEEK AS A RIDGE OF HIGH
PRESSURE BUILDS OVER THE REGION.

&&

.DISCUSSION...AS OF 01:50 PM PST SATURDAY...LIGHT RAIN CONTINUES
TO IMPACT PORTIONS OF THE REGION THIS AFTERNOON...MAINLY SOUTH OF
THE SAN FRANCISCO BAY AREA AS A WEAK FRONTAL BOUNDARY ADVANCES
SOUTHWARD. WILL SEE PRECIPITATION COMING TO AN END REGION-WIDE
THROUGH THE EVENING AND ESPECIALLY BY TONIGHT WITH DRYING
CONDITIONS IN THE BOUNDARY LAYER. WHILE PATCHY FOG WILL BE
POSSIBLE EARLY SUNDAY MORNING ACROSS PORTIONS OF THE NORTH BAY
AND OTHER INLAND VALLEY LOCATIONS...DO NOT EXPECT FOG TO BE A
WIDESPREAD ISSUE.

DRY CONDITIONS WILL THEN PREVAIL FOR THE REMAINDER OF THE WEEKEND
AS A MID/UPPER LEVEL RIDGE DEVELOPS OVER THE PACIFIC AND BUILD
EASTWARD TOWARD THE CALIFORNIA COAST. FORECAST MODELS CONTINUE TO
AGREE THAT THE RIDGE WILL STRENGTHEN THROUGH MIDWEEK WITH THE
RIDGE AXIS BECOMING POSITIONED ALONG THE WEST COAST TUESDAY INTO
WEDNESDAY. 850MB TEMPERATURES ARE ALSO FORECAST TO WARM TO NEAR
OR ABOVE 17 DEGREES C WITH WEAK OFFSHORE FLOW DEVELOPING ALOFT
AND MIXING DOWN TO THE SURFACE. THIS WILL RESULT IN TEMPERATURES
WARMING INTO THE LOWER 70S NEAR THE COAST TO THE UPPER 70S TO
NEAR 80 INLAND...A GOOD 10 DEGREES ABOVE AVERAGE. THE RIDGE IS
THEN FORECAST TO SHIFT INLAND AND BREAK DOWN LATE IN THE WEEK
AHEAD OF A DEVELOPING MID/UPPER LEVEL TROUGH OVER THE EASTERN
PACIFIC. THIS WILL ALLOW THE WARMING TREND TO END...YET
TEMPERATURES WILL REMAIN ABOVE AVERAGE ON THANKSGIVING DAY.

THE MEDIUM RANGE MODELS ARE IN DECENT AGREEMENT WITH UNSETTLED
WEATHER RETURNING TO NORTHERN CALIFORNIA AS EARLY AS FRIDAY.
WHILE THERE REMAIN SOME DIFFERENCES IN TIMING AND POSITION OF THE
GREATEST MOISTURE ADVECTION...THE GFS AND ECMWF BOTH SHOW A
POTENT MID/UPPER LEVEL LOW OFF THE PACIFIC NORTHWEST COAST LATE
IN THE FORECAST PERIOD WITH EMBEDDED DISTURBANCES MOVING INTO THE
REGION. HAVE INCREASED PRECIPITATION CHANCES FOR FRIDAY AND
SATURDAY...ESPECIALLY FOR THE SANTA CRUZ MOUNTAINS NORTHWARD.
WILL HAVE TO MONITOR THE LATEST AS UNSETTLED CONDITIONS AND
WIDESPREAD RAINFALL MAY CONTINUE INTO THE FIRST WEEK OF DECEMBER.

&&

.AVIATION...AS OF 5:15 PM PST SATURDAY...MVFR/VFR CONDITIONS ARE
PRESENTLY REPORTED. SURFACE TO LOWER LEVEL W-NW WINDS ARE FAIRLY
WELL LINKED...BUT THE WINDS SHOULD GRADUALLY DE-COUPLE AS NIGHT-TIME
COOLING SETS IN. AT PRESENT A NW SURFACE WIND IS HELPING TO DRY THE
NORTH BAY WITH LITTLE CHANGE NOTED IN THE HUMDIITY OVER THE REMAINDER
OF THE AREA. AS MENTIONED IN THE EARLIER AVIATION DISCUSSION WILL
NEED TO MONITOR FOR POSSIBLE FOG FORMATION VERY LATE TONIGHT. PER
MODEL GUIDANCE SURFACE WINDS IT APPEARS THE BEST CHANCE FOR FOG
FORMATION TONIGHT WOULD BE AFTER 08Z WHEN THE WINDS SETTLE BACK TO
2 TO 5 KNOTS. VERY LIGHT MIXING IS FAVORABLE FOR FOG VERSUS CALM
WINDS WHICH ARE NOT QUITE AS FAVORABLE EXCEPT FOR INSTANCES OF
SHALLOW GROUND FOG. ANY FOG LATE TONIGHT/EARLY SUN MORNING SHOULD
BE PATCHY AT BEST AS PROCESSES FOR EITHER ADVECTION FOG OR RADIATIONAL
FOG LOOK TO BE TEMPERED THROUGH THE NIGHT.

VICINITY OF KSFO...MODERATE TO HIGH CONFIDENCE VFR FORECAST.  WEST
WINDS HAVE PICKED UP RECENTLY WITH GUSTS JUST UP OVER 20 KNOTS. THE
WINDS SHOULD SETTLE BACK UNDER 20 KNOTS THROUGH THE EVENING BUT THE
TIMING IS LOW CONFIDENCE BECAUSE IN THIS FLOW PATTERN ANY ADDITIONAL
TROUGH MOVING QUICKLY OVER THE AREA COULD LEAD TO ABRUPTLY INCREASED
WEST WINDS AGAIN OVERNIGHT.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...MVFR/VFR CONDITIONS FOR THE FORECAST
PERIOD. LOW TO MODERATE CONFIDENCE.

&&

.MARINE...AS OF 01:50 PM PST SATURDAY...WINDS SHIFT TO NORTH-
NORTHWEST OVER THE COASTAL WATERS TODAY IN THE WAKE OF A FRONTAL
PASSAGE. BRIEF GUSTS 20-30KT MAY ACCOMPANY THE FRONTAL PASSAGE.
INCREASING WINDS AND BUILDING NORTHWEST SWELL ARE EXPECTED
SATURDAY EVENING INTO SUNDAY MORNING BEFORE TAPERING OFF LATE
SUNDAY.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TNGT...SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 7 PM UNTIL 1 AM
             SCA...PT REYES TO PIGEON PT 0-10 NM UNTIL 1 AM
             SCA...PT ARENA TO PT REYES 10-60 NM UNTIL 1 AM
             SCA...PT REYES TO PIGEON PT 10-60 NM
             SCA...PIGEON PT TO PT PINOS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 7 PM
             SCA...PT ARENA TO PT REYES 0-10 NM UNTIL 7 PM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM

&&

$$

PUBLIC FORECAST: RGASS
AVIATION: CANEPA
MARINE: DRP

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