245
FXUS66 KMTR 191157
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
357 AM PST THU DEC 19 2024
..NEW SYNOPSIS, SHORT TERM, LONG TERM, AVIATION, MARINE
SYNOPSIS
ISSUED AT 351 AM PST THU DEC 19 2024
PATCHY DENSE FOG EARLY THIS MORNING FROM THE NORTH BAY VALLEYS
SOUTH INTO THE SOUTH BAY VALLEYS IS EXPECTED TO PERSIST THROUGH
THE LATE MORNING. ONE MORE DAY OF ABOVE NORMAL TEMPERATURES FOR
MOST OF OUR INTERIOR LOCATIONS BEFORE THE FIRST OF NUMEROUS
DISTURBANCES, APPROACHES OUR AREA LATE FRIDAY NIGHT INTO EARLY
SATURDAY MORNING.
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 351 AM PST THU DEC 19 2024
DENSE FOG HAS BEEN SLOWER TO DEVELOP AND SPREAD ACROSS OUR AREA
TONIGHT, WITH CIRRUS CONTINUING TO STREAM ACROSS THE SOUTH BAY
SLOWING RADIATIVE COOLING AS OF 3AM. DENSE FOG HAS DEVELOPED ACROSS
SOME OF THE CLOUD FREE AREAS OVER THE NORTH BAY AND EAST BAY AND
WILL EVENTUALLY FILL ACROSS THE SOUTH BAY AS THE HIGH CLOUDS SHIFT
EAST. A DENSE FOG ADVISORY REMAINS IN EFFECT THROUGH NOON PST TODAY.
HIRES GUIDANCE SUGGEST MOST OF THE FOG DISSIPATING OR MIXING OUT BY
NOON TODAY, WITH A CHANCE OF LINGERING FOG OR REDEVELOPMENT OVER
PORTIONS OF MARIN CO THROUGH THE AFTERNOON. TEMPERATURES THIS
AFTERNOON ACROSS THE NORTH BAY WILL BE VERY SIMILAR TO YESTERDAY
WITH HIGHS IN THE LOW/MID 60S, COOLER ALONG THE COAST AND BAY AREA
WHERE GRADUALLY INCREASING CLOUDS WILL HELP TO KEEP TEMPERATURES
AROUND NORMAL. INTERIOR LOCATIONS ACROSS THE SOUTH BAY AND THE
REMAINDER OF THE CENTRAL COAST WILL WARM NICELY INTO THE LOW 70S.
AREAS OF DENSE FOG ARE POSSIBLE AGAIN IN THE NORTH AND SOUTH BAY
VALLEYS LATE TONIGHT INTO EARLY FRIDAY MORNING. BY LATE TOMORROW
MORNING, THE WELL ADVERTISED PATTERN CHANGE WILL BEGIN TO TAKE SHAPE
AS SOUTHERLY OFFSHORE SURFACE FLOW OUT AHEAD OF THE STRENGTHENING
SYSTEM INCREASES TO 15-20MPH THROUGH THE REMAINDER OF THE DAY INTO
SATURDAY.
LONG TERM
(FRIDAY THROUGH WEDNESDAY)
ISSUED AT 351 AM PST THU DEC 19 2024
THE FIRST OF SEVERAL IMPACTFUL ROUNDS OF RAIN AND WIND TAKES AIM
ACROSS OUR AREA LATE FRIDAY NIGHT INTO EARLY SATURDAY. THE SYSTEM IS
TRENDING MORE PROGRESSIVE AND HAS SHIFTED SLIGHTLY NORTH, WHICH HAS
RESULTED IN A SLIGHT DOWNWARD TREND IN EXPECTED RAINFALL AMOUNTS
THROUGH SATURDAY NIGHT OVER THE NORTH BAY. SCATTERED LIGHT RAIN WILL
PERSIST THROUGH THE NIGHT INTO EARLY SUNDAY AS A SERIES OF MIDLEVEL
SHORTWAVES EJECT OUT AHEAD OF A STRENGTHENING BAROCLINIC ZONE AND
TIGHTENING THETAE GRADIENT, THAT PUSHES ONSHORE SUNDAY NIGHT.
ALTHOUGH LIGHT RAIN CHANCES REMAIN IN THE FORECAST DURING THE DAY
ON MONDAY, THE LEADING EDGE OF A STRONG AR BEGINS TO IMPACT OUR
AREA MONDAY EVENING THROUGH TUESDAY, WITH STRONG WINDS UP TO
30-40MPH AT TIMES THROUGHOUT THE EVENT AND 2-4" OF RAINFALL ACROSS
THE NORTH BAY. PROGRESSIVE UPPER RIDGING ACROSS OUR AREA ON
CHRISTMAS DAY PROVIDES A SHORT BUFFER BEFORE THE NEXT SYSTEM
ARRIVES AFTER MIDNIGHT INTO THE EARLY HOURS OF THURSDAY.
AVIATION
(12Z TAFS)
ISSUED AT 351 AM PST THU DEC 19 2024
FOG CONTINUES TO SPREAD INTO THE NORTH BAY AND EAST BAY WITH HIGHEST
CONFIDENCE IN FOG REACHING STS, APC, AND LVK. CONFIDENCE IS SLIGHTLY
LOWER FOR SFO, OAK, AND SJC WITH ENSEMBLE AND LAMP GUIDANCE LEANING
MORE TOWARDS 4-5SM VISIBILITIES. THE NAMNEST CONTINUES TO SHOW
WIDESPREAD FOG IMPACTING THE BAY AREA AIRPORTS BUT FOG HAS BEEN MUCH
SLOWER TO DEVELOP TONIGHT, IN PART DUE TO DRIER CONDITIONS, WHICH
DECREASES CONFIDENCE IN THIS SOLUTION. IF FOG IS GOING TO DEVELOP AT
SFO, OAK, AND SJC IT WILL MOST LIKELY BE BETWEEN 14-18Z AROUND
SUNRISE SO WILL CONTINUE TO MONITOR AND UPDATE AS NEEDED. VFR
CONDITIONS RETURN MID MORNING WITH A MIX OF MVFR TO LIFR CONDITIONS
EXPECTED AGAIN OVERNIGHT. MODERATE OFFSHORE WINDS ARE POSSIBLE
DURING THE DAY BUT WILL REMAIN LIGHT AND VARIABLE OVERNIGHT.
VICINITY OF SFO...VFR WITH SOME POTENTIAL FOR MVFR-IFR CONDITIONS
THROUGH LATE THIS MORNING. ENSEMBLE GUIDANCE SHOWS VISIBILITIES
DROPPING TO 4-5SM THIS MORNING WITH 14-18Z AS THE MOST LIKELY
TIMEFRAME FOR VISIBILITIES TO DROP. IT IS WORTH NOTING THAT SOME
MODELS (NAMNEST) DO SHOW FOG MOVING INTO SFO, HOWEVER, FOG HAS BEEN
MUCH SLOWER TO ARRIVE THAN FORECAST IN THIS MODEL. CONDITIONS REMAIN
DRIER TODAY THAN THEY WERE AT THIS TIME YESTERDAY WITH FOG JUST NOW
FILLING INTO THE EAST BAY. GIVEN THE DRIER CONDITIONS, CONFIDENCE IS
LOWER THAT 1/4SM FOG WILL DEVELOP AT SFO BUT WILL CONTINUE TO
MONITOR.
SFO BRIDGE APPROACH...SIMILAR TO SFO. SOME POTENTIAL FOR FOG TO
DEVELOP ACROSS THE SF BAY BETWEEN 14-18Z BUT CONFIDENCE REMAINS LOW
TO MODERATE.
MONTEREY BAY TERMINALS...VFR CONTINUES THROUGH EARLY TOMORROW
MORNING. LIGHT OFFSHORE FLOW CONTINUES AT MRY THROUGH THE TAF
PERIOD. MODERATE SE DRAINAGE WINDS WILL CONTINUE AT SNS THROUGH LATE
THIS MORNING, WEAKEN SLIGHTLY DURING THE DAY, AND STRENGTHEN AGAIN
OVERNIGHT. ENSEMBLE GUIDANCE SUPPORTS A RETURN OF OVERCAST
CONDITIONS TOWARDS THE END OF THE TAF PERIOD (10-12Z) WITH CIGS
DROPPING TO AROUND 2500 FEET.
MARINE
(TODAY THROUGH TUESDAY)
ISSUED AT 351 AM PST THU DEC 19 2024
CONTINUED MODERATE TO LONG PERIOD NORTHWESTERLY SWELL WILL CAUSE
AN INCREASE IN SHOALING ON HARBOR ENTRANCES AND ELEVATED SNEAKER
WAVE RISK ALONG THE COASTLINE. LIGHT TO MODERATE RAIN ARRIVES
ALONG WITH STRONG WINDS AND ELEVATED WAVE HEIGHTS BETWEEN 15 TO
19 FEET LATE FRIDAY THROUGH THE WEEKEND. THE STORM DOOR WILL THEN
REMAIN OPEN WITH ANOTHER, STRONGER, SYSTEM EXPECTED MONDAY INTO
TUESDAY AND A THIRD SYSTEM POSSIBLE LATE WEEK. WAVE HEIGHTS WILL
REMAIN ELEVATED THROUGH LATE NEXT WEEK WITH ANOTHER ROUND OF 15
TO 20 FEET WAVES EXPECTED MONDAY THROUGH WEDNESDAY. PERSISTENT
DANGEROUS CONDITIONS FOR SMALL CRAFTS ARE EXPECTED FRIDAY INTO
NEXT WEEK.
BEACHES
ISSUED AT 1036 AM PST WED DEC 18 2024
A BEACH HAZARDS STATEMENT WILL BE IN EFFECT FROM 6 PM TODAY TO 6 PM
THURSDAY FROM SONOMA COUNTY TO MONTEREY COUNTY. MODERATE TO LONG
PERIOD NORTHWESTERLY SWELL WILL RESULT IN ELEVATED SNEAKER WAVE
DEVELOPMENT WITH SNEAKER WAVES LIKELY TO BREAK BETWEEN 10 AND 13
FEET. THE COMBINATION OF ELEVATED SNEAKER WAVE THREAT AND RIP
CURRENTS BOTH POSE A RISK TO BEACHGOERS WHO ARE CAUGHT UNAWARE.
VISITORS TO THE COAST MIDWEEK ARE ADVISED TO TAKE EXTRA CARE AND
NEVER TURN THEIR BACKS TO THE OCEAN AS SNEAKER WAVES MAY SWEEP
UNAWARE BEACHGOERS INTO THE OCEAN.
A SECOND PERIOD OF DANGEROUS, ELEVATED SURF NEAR 15 FEET WILL OCCUR
SATURDAY INTO SUNDAY AS ANOTHER SYSTEM APPROACHES THE WEST COAST.
THEN, A VERY LARGE AND POWERFUL, LONG PERIOD WEST SWELL TRAIN
WILL LIKELY ARRIVE ALONG OUR ENTIRE COASTLINE MONDAY INTO TUESDAY
NEXT WEEK. CURRENT GLOBAL WAVE MODELS ARE FORECASTING SWELL HEIGHTS
TO 20+ FEET WITH VERY ENERGETIC SWELL PERIODS OF 20+ SECONDS, THIS
WILL LEAD TO MUCH HIGHER BREAKERS INCLUDING LOCALIZED COASTAL FLOODING
IMPACTS. STAY TUNED FOR FURTHER UPDATES.
MTR WATCHES/WARNINGS/ADVISORIES
CA...BEACH HAZARDS STATEMENT THROUGH THIS AFTERNOON FOR CAZ006-505-
509-529-530.
DENSE FOG ADVISORY UNTIL NOON PST TODAY FOR CAZ006-506-508-510-
513.
PZ...SMALL CRAFT ADVISORY FROM 3 AM TO 3 PM PST FRIDAY FOR PT ARENA
TO PT REYES 10-60 NM.
SHORT TERM...JM
LONG TERM....JM
AVIATION...KENNEDY
MARINE...KENNEDY
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