615
FXUS66 KMTR 281825
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1025 AM PST SUN DEC 28 2025
..NEW AVIATION, MARINE, BEACHES
KEY MESSAGES
UPDATED AT 235 AM PST SUN DEC 28 2025
- DRY WEATHER, WITH COLD NIGHTS THROUGH WEDNESDAY MORNING.
- INCREASING CONFIDENCE IN WET WEATHER RETURNING MID TO LATE WEEK,
DUE TO A PATTERN CHANGE.
SHORT TERM
ISSUED AT 235 AM PST SUN DEC 28 2025
(TODAY AND TONIGHT)
HIGH CLOUDS ARE VISIBLE ON SATELLITE IMAGERY THIS MORNING, CURRENTLY
TRACKING INTO THE BAY AREA. THIS HAS MADE FOR AN INTERESTING
FORECAST AROUND THESE AREAS, PARTICULARLY THE NORTH BAY WHERE FOG
HAS DEVELOPED. POCKETS OF COLDER AIR CAN BE FOUND THERE, BUT AS OF
THIS TIME, NOT ENOUGH TO WARRANT A COLD WEATHER ADVISORY. IN FACT,
LOOKING SOUTH TO WHERE THE COLD WEATHER ADVISORY IS IN PLACE,
TEMPERATURES GENERALLY LOOK TO BE ON TRACK. THERE IS SOME CONCERN
FOR THE LOW TEMPERATURE FORECAST AROUND THE NORTH SALINAS VALLEY AND
AREAS NEAR HOLLISTER GIVEN DEW POINTS HAVEN'T REALLY FALLEN PAST THE
UPPER 30S AT THIS TIME. DEPENDING ON HOW TEMPERATURES PAN OUT THIS
MORNING, WE MAY BE ABLE TO END THE COLD WEATHER ADVISORY EARLY IF
TEMPERATURES DON'T FALL.
LOOKING AT THE REST OF TODAY, HIGH CLOUDS CONTINUE TO ADVANCE
SOUTHWARDS. HIGH PRESSURE BUILDS OVER THE EASTERN PACIFIC WHICH WILL
PINCH OFF PART OF THE UPPER LEVEL TROUGH. HIGHS TODAY WILL BE A FEW
DEGREES WARMER THAN YESTERDAY. AN AREA TO WATCH WILL BE SUNDAY NIGHT
INTO MONDAY. RIDGING CONTINUES TO BUILD IN OVER NORTHERN CALIFORNIA,
AND ANOTHER UPPER LEVEL TROUGH FORMS OVER THE SIERRA, GETS CUT OFF,
AND THEN PUSHES INTO SOUTHERN CALIFORNIA. THIS SHOULD ALLOW FOR
MOSTLY CLEAR SKIES AND PERHAPS SOME WEAK OVERNIGHT OFFSHORE FLOW.
THE LOW TEMPERATURE FORECAST WILL BE THE OTHER CHALLENGE IN THE NEAR
TERM. RIGHT NOW WE FLIRT WITH COLD WEATHER ADVISORY CONDITIONS OVER
THE NORTH AND EAST BAY VALLEYS, AS WELL AS THE SOUTHERN SALINAS
VALLEY. GIVEN SOME OF THE GUIDANCE FROM THE MOS HAS TRENDED A BIT
WARMER, OPTED TO NOT ISSUE ANYTHING THIS FAR OUT. THE COLDEST
TEMPERATURES FROM THESE AREAS LOOK TO BE BETWEEN ROUGHLY AROUND 12-
15Z, BEFORE WARMING ABOVE CRITERIA BY LATE MORNING.
LONG TERM
ISSUED AT 235 AM PST SUN DEC 28 2025
(MONDAY THROUGH SATURDAY)
RIDGING HOLDS THROUGH TUESDAY, BEFORE IT GETS PUSHED OVER THE PACNW.
TO THE NORTH, LOW PRESSURE FROM THE GULF OF ALASKA FORMS AND BEGINS
TO DIGS SOUTHWARDS. TO THE SOUTH, THE CUT OF LOW MEANDERS AND SLOWLY
DRIFTS NORTHWARD. THIS SYSTEM SHOULD GET PICKED UP BY DIGGING TROUGH
TO OUR NORTH. ENSEMBLES FAVOR WETTER WEATHER STARTING WEDNESDAY,
WITH THE QPF CLUSTERS SHOWING A SPREAD OF RAIN SOLUTIONS ACROSS
CALIFORNIA. THE NBM GUIDANCE MATCHES THIS, THUS OPTED TO LEAVE THAT
IN. LOOKING AT THE GEFS AND ECMWF ENSEMBLE, PERIODIC ROUNDS OF RAIN
LOOK POSSIBLE THROUGH THE WEEKEND. TIMING, PLACEMENT, AND INTENSITY
WILL CONTINUE TO UNFOLD AS WE GET CLOSER TO THE EVENT.
AVIATION
(06Z TAFS)
ISSUED AT 935 PM PST SAT DEC 27 2025
THE LARGER SCALE WMC-SFO PRESSURE GRADIENT WILL STRENGTHEN TONIGHT
THROUGH SUNDAY NIGHT RESULTING IN OFFSHORE WINDS REACHING THE BAY
AREA. A MAINLY CLEAR SKY WILL HELP WITH RADIATIVE COOLING AND
PATCHY FOG REDEVELOPMENT TONIGHT AND SUNDAY MORNING. WILL ALSO
HAVE TO MONITOR TULE FOG REDEVELOPMENT IN THE CENTRAL VALLEY AND
THE POTENTIAL FOR A RETURN OF TULE FOG INTO THE BAY AREA, THOUGH
AT THE TIME BEING THE HRRR MODEL SHOWS GREATER TULE FOG DEVELOPMENT
SUNDAY NIGHT INTO MONDAY. THE OFFSHORE WINDS DEVELOP BEFORE THEN,
TULE FOG DEVELOPMENT AND TRANSPORT OF TULE FOG COULD START AS SOON
AS EARLY SUNDAY MORNING DUE TO RECENT RAINS AND MOISTENED BOUNDARY
LAYER. KSTS AND KAPC HAVE FOG IN THE TAFS DUE TO NOCTURNAL RADIATIVE
COOLING, OTHERWISE IT'S A MODERATE TO HIGH CONFIDENCE VFR FORECAST
FOR THE REMAINDER OF THE TERMINALS.
VICINITY OF SFO...VFR. MAINLY NORTHEAST WINDS 5-7 KNOTS TONIGHT
THROUGH SUNDAY NIGHT.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR. WINDS EAST-SOUTHEAST 5-10 KNOTS AND
CONTINUING INTO EARLY-MID SUNDAY AFTERNOON, THEN BECOMING LIGHT
AND VARIABLE TO LIGHT ONSHORE IN THE LATE AFTERNOON. LIGHT EAST TO
SOUTHEAST WINDS REDEVELOP SUNDAY NIGHT.
AVIATION
(18Z TAFS)
ISSUED AT 945 AM PST SUN DEC 28 2025
AFTER SOME LINGERING FOG DISSIPATES AT STS THIS MORNING, VFR
CONDITIONS AND GENTLE WINDS WILL PERSIST THROUGH THE AFTERNOON. A
STRENGTHENING OFFSHORE GRADIENT WILL BRING DRIER AIR AND SOME
MODERATE EASTERLY WINDS TO EXPOSED TERMINALS THIS EVENING. WITH A
LONG, CLEAR NIGHT, TULE FOG IS LIKELY TO DEVELOP IN THE CENTRAL
VALLEY. EASTERLY WINDS SHOULD BE LIGHTER SUNDAY MORNING, WHICH
COULD HELP ADVECT SOME OF THIS FOG INTO THE INTERIOR EAST BAY,
POTENTIALLY IMPACTING LVK. THERE IS A GOOD CHANCE FOR PURE
RADIATION FOG TO RETURN TO THE NORTH BAY EARLY MONDAY MORNING,
WITH ONLY A SLIGHT CHANCE ACROSS THE BAY AREA TERMINALS.
VICINITY OF SFO...THE TERMINAL IS MOSTLY CLEAR, AS SOME LOW CLOUDS
OVER THE BAY RETREAT NORTH. THE WIND DIRECTION IS A LITTLE TRICKY
TODAY AS THE INCREASING EASTERLY GRADIENT FIGHTS THE SEA BREEZE
EFFECT IN THE AFTERNOON. EITHER WAY THE ACTUAL SPEED SHOULD
REMAIN GENTLE TO MODERATE THROUGH THE DAY WITH NO SIGNIFICANT
IMPACTS EXPECTED.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...HIGH CONFIDENCE IN VFR CONDITIONS THROUGH
THE TAF PERIOD. EASTERLY WINDS SHOULD FLIP ONSHORE FOR A FEW HOURS
THIS AFTERNOON BEFORE FLIPPING BACK OFFSHORE OVERNIGHT. THE
BUILDING PRESSURE GRADIENT COMBINED WITH THE TYPICAL DRAINAGE FLOW
COULD BRING SUSTAINED WINDS TO 10-15 KNOTS AT SNS SUNDAY MORNING.
MARINE
(TODAY THROUGH FRIDAY)
ISSUED AT 945 AM PST SUN DEC 28 2025
A GENTLE NORTHERLY BREEZE WILL GRADUALLY SHIFT TO EASTERLY OVER
THE NEXT 24 HOURS. SEAS WILL REMAIN MODERATE THROUGH THURSDAY.
OVERALL MARINE CONDITIONS WILL REMAIN FAVORABLE BEFORE THE NEXT
LOW PRESSURE SYSTEM BRINGS STRONG SOUTHERLY WINDS AND ROUGH SEAS
BY FRIDAY.
BEACHES
ISSUED AT 945 AM PST SUN DEC 28 2025
PERIGEAN SPRING TIDES (KING TIDES) RETURN WEDNESDAY - SUNDAY.
THIS IS DUE TO THE COMBINATION OF THE FULL MOON ON 1/3, LUNAR
PERIGEE ON 12/31, AND PERIHELION ON 1/3. IN OTHER WORDS ALL THREE
PLANETARY BODIES ARE LINED UP AND CLOSE TO EACH OTHER. IN
ADDITION TO THE HIGH ASTRONOMICAL TIDE, THE INCOMING LOW PRESSURE
SYSTEM WILL BRING STRONG ONSHORE WINDS, GENERATING SOME STORM
SURGE. THE COMBINATION OF THESE FACTORS WILL BRING MINOR COASTAL
FLOODING TO THE LOW-LYING AREAS NEAR SHORELINES AND TIDAL
WATERWAYS DURING HIGH TIDE WEDNESDAY THROUGH SUNDAY. AT THE SAN
FRANCISCO TIDAL GAUGE, HIGH TIDE IS EXPECTED TO BE 1.5 FT ABOVE
NORMAL AT 7:51 AM WEDNESDAY, 1.7 FT ABOVE NORMAL AT 8:41 AM
THURSDAY, 1.8 FT ABOVE NORMAL AT 9:34 AM FRIDAY, 1.8 FT ABOVE
NORMAL AT 10:26 AM SATURDAY, AND 1.6 FT ABOVE NORMAL AT 11:18 AM
SUNDAY. THESE PREDICTIONS INCLUDE 0.5 FEET OF STORM SURGE THAT
WILL ENHANCE THE ASTRONOMICAL TIDE AND FLOODING THREAT. HIGH TIDE
VARIES UP TO 90 MINUTES EARLIER OR LATER ALONG THE PACIFIC COAST
AND THROUGH THE SAN FRANCISCO BAY, RESPECTIVELY.
MTR WATCHES/WARNINGS/ADVISORIES
CA...COASTAL FLOOD ADVISORY FROM 5 AM WEDNESDAY TO 2 PM PST SUNDAY
FOR CAZ006-505-506-508-509-529-530.
PZ...NONE.
SHORT TERM...KR
LONG TERM....KR
AVIATION...FLYNN
MARINE...FLYNN
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