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

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000
FXUS66 KMTR 221221
AFDMTR

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA
421 AM PST MON DEC 22 2014

.SYNOPSIS...DRY AND MILD WEATHER FOR THE START OF THE WORK WEEK AS
HIGH PRESSURE BUILDS OVER THE AREA. HIGHER THAN AVERAGE TIDES WILL
RESULT IN MINOR COASTAL FLOODING TODAY AND TOMORROW. TEMPERATURES
WARM THROUGH MIDWEEK BEFORE A STORM BRUSHES PAST THE AREA BRINGING A
CHANCE OF RAIN AND COOLING TEMPERATURES TO NEAR SEASONAL NORMALS.

&&

.DISCUSSION...AS OF 3:20 AM PST MONDAY...MILD TEMPERATURES
CONTINUE THIS MORNING ACROSS THE AREA WITH MOST OF THE REGION
STILL IN THE MID TO UPPER 50S. PATCHY FOG AND LOW CLOUDS HAVE
FORMED ACROSS MUCH OF THE AREA OVERNIGHT. DENSE FOG HAS BEEN
LIMITED TO NORTH BAY VALLEYS AND PORTIONS OF THE COAST THUS FAR
HOWEVER. THERE HAVE BEEN A FEW BUCKET TIPS OF DRIZZLE AS
WELL...MOSTLY NEAR THE COAST.

MINOR COASTAL FLOODING WILL AGAIN BE POSSIBLE TODAY ALONG THE
COASTLINE AND THE BAY SHORE. PERIGEAN SPRING TIDES...ALSO CALLED
KING TIDES...WILL CAUSE INUNDATION OF LOW LYING COASTAL AREAS.
YESTERDAY SAW SOME ISSUES INCLUDING ROADS CLOSED IN FREQUENT
TROUBLE SPOTS IN THE NORTH BAY AND WATER LAPPING ONTO THE
EMBARCADERO IN SAN FRANCISCO. THIS MORNINGS HIGH TIDE WILL BE THE
HIGHEST SINCE AUGUST. SEE THE COASTAL FLOOD ADVISORY FOR MORE
INFORMATION.

A RIDGE WILL CONTINUE TO BUILD OVER CALIFORNIA FOR THE START OF
THE WEEK LEADING TO DRY WEATHER AND INCREASING TEMPERATURES.
TUESDAY WILL BE THE WARMEST DAY OF THE WEEK FOR MOST AREAS BEFORE
A COOLER AIRMASS BEGINS TO NUDGE SOUTHWARD.

BY MIDWEEK THE RIDGE BREAKS DOWN AND AN INSIDE SLIDER DIGS
SOUTHEAST THROUGH THE WESTERN STATES JUST BRUSHING THE NORTHERN
AND EASTERN EDGES OF THE CWA. THE AFTERNOON RUNS OF THE GLOBAL
MODELS HAVE INCREASED THE STRENGTH OF THE STORM AND HAVE MORE
PRECIP INTO THE DISTRICT HOWEVER THE NAM DOES NOT HAVE THE SAME
INTENSITY. NAEFS PROBABILITY OF MEASURABLE RAIN IN THE NORTH BAY
HAS INCREASED SIGNIFICANTLY THOUGH FOR SAN FRANCISCO IT IS STILL
AROUND 10 PERCENT. FOR NOW HAVE INCREASED RAIN CHANCES IN THE
NORTH BAY AND FAR EAST BAY AS THE SYSTEM GOES BY HOWEVER
CONFIDENCE REMAINS LOW. ANY RAIN THAT DOES FALL WILL BE VERY LIGHT
SO THE PRIMARY IMPACT WILL BE THE COOLER AIRMASS. BY THURSDAY
NIGHT TEMPERATURES IN NORTH BAY VALLEYS WILL LIKELY DIP INTO THE 30S.

RIDGING OFFSHORE WILL CONTINUE THROUGH THE END OF THE WEEK AND
TEMPERATURES REMAIN NEAR NORMAL. GLOBAL MODELS DEPICT ANOTHER
INSIDE SLIDER BY THE WEEKEND BRINGING ANOTHER CHANCE OF RAIN.

&&

.AVIATION...AS OF 4:15 AM PST MONDAY...MAIN CONCERN THIS MORNING
IS THE LOW LEVEL MOISTURE CAUSING LOCAL FOG AROUND THE SFO AND MRY
BAY AREA. THE COMBINATION OF LIGHT WIND AND BUILDING HIGH PRESSURE
ALOFT HAS ALLOWED FOG TO FORM IN THE EAST BAY AS WELL AS THE MRY
BAY AREA THIS MORNING. VSBYS HAVE DROPPED TO 1/4-1/2 MILE AT OAK.
THE 12Z METAR AT SFO SHOWS VSBY IS 10 MILES BUT THE CIGS HAVE
LIFTED AND DEWPT/TEMP SPREAD IS LESS THAN 1 DEGREE. THIS WILL
ALLOW FOR SOME RADIATIONAL COOLING WHICH COULD BRING FOG INTO SFO
BETWEEN 13Z AND 17Z. VSBYS EXPECTED TO IMPROVE AFTER 17Z BUT LOW
CIGS IN THE IFR RANGE WILL LINGER THROUGH AT LEAST 19Z.

VICINITY OF KSFO...IFR CIGS WITH VSBYS DROPPING AS LOW AS 1/2 TO
3 MILES THROUGH 17Z. VSBYS IMPROVING AFTER 17Z TO 3-5 MILES AFTER
17Z BUT REMAINING IFR THROUGH 19Z. MVFR CIGS AFTER 19Z. POSSIBLE
CLEARING OF THE CIGS LATE IN THE AFTERNOON IF THE SEABREEZE IS
STRONG ENOUGH.

KSFO BRIDGE APPROACH...SIMILAR TO KSFO.

MONTEREY BAY AREA TERMINALS...LIFR CIGS AND VSBYS THROUGH 17Z.
LIFR FOR CIGS THROUGH 19Z. IFR CIGS AFTER 19Z BECOMING MVFR TO VFR
AFTER 21Z.

&&

.MARINE...AS OF 3:01 AM PST MONDAY...HIGH PRESSURE BUILDING OFF
THE CALIFORNIA COAST WILL RESULT IN INCREASING NORTHWEST WINDS
OVER THE SOUTHERN AND OUTER WATERS THIS AFTERNOON THROUGH MONDAY.
WINDS WILL DECREASE BY TUESDAY NIGHT AS THE HIGH MOVES INTO THE
GREAT BASIN. WINDS WILL INCREASE AGAIN BY THURSDAY AS ANOTHER HIGH
STRENGTHENS OVER THE EASTERN PACIFIC.

&&

.MTR WATCHES/WARNINGS/ADVISORIES...
     .TDAY...COASTAL FLOOD ADVISORY...COASTAL AND BAY SHORE AREAS
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM
             SCA...PIGEON PT TO PT PINOS 10-60 NM
             SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM
             SCA...PT ARENA TO PT REYES 0-10 NM FROM 2 PM
             SCA...PT REYES TO PIGEON PT 0-10 NM FROM 2 PM
             SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 2 PM
             SCA...PT ARENA TO PT REYES 10-60 NM FROM NOON
             SCA...PT REYES TO PIGEON PT 10-60 NM FROM NOON

&&

$$

PUBLIC FORECAST: AC
AVIATION/MARINE: W PI

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