951
FXUS66 KMTR 051129
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
329 AM PST MON JAN 5 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1203 AM PST MON JAN 5 2026
- RAIN RETURNS TODAY WITH URBAN AND MINOR RIVER FLOODING
POSSIBLE, PARTICULARLY IN THE NORTH BAY
- ONE LAST DAY WITH COASTAL FLOODING FROM KING TIDES AND STORM
SURGE IN THE SAN FRANCISCO BAY
- HAZARDOUS BEACH CONDITIONS THURSDAY - FRIDAY
- DRIER WEATHER MOVES IN TUESDAY AND REMAINS THROUGH NEXT WEEK
- COLD MORNING TEMPERATURES STARTING THURSDAY
SHORT TERM
ISSUED AT 1203 AM PST MON JAN 5 2026
(TODAY AND TONIGHT)
IN A WORD, WET. THE NEXT ORGANIZED BAND OF SHOWERS WILL MOVE
THROUGH WITH THE PASSAGE OF A COLD FRONT TODAY. THE CURRENT RADAR
DATA SHOWS A PRETTY WELL-BEHAVED WARM SECTOR RAIN BAND COMING INTO
RANGE. THERE HAVE BEEN A FEW LIGHTNING STRIKES OVER THE OCEAN
BEHIND THE FRONT NEAR A MATURE EXTRATOPRICAL CYCLONE. IT'S UNCLEAR
IF THE CONVECTION WILL BE AS DEEP OVER LAND WHERE THE INSTABILITY
IS WEAKER, BUT THIS LOW PRESSURE SYSTEM WILL ENHANCE THE RAIN TO
SOME DEGREE THIS AFTERNOON. THE NORTH BAY WILL BE HIT THE HARDEST
TODAY, WITH 1-2" EXPECTED IN THE LOWER ELEVATIONS, AND UP TO 4" IN
THE MOUNTAINS. THE RAIN WILL START THERE AS EARLY AS 2 AM, AND
CONTINUE OFF-AND-ON THROUGH THE ENTIRE DAY. MINOR URBAN AND SMALL
STREAM FLOODING IS EXPECTED, AND THERE IS A SLIGHT CHANCE FOR THE
LARGER RIVERS TO REACH MINOR FLOOD STAGE. THE REST OF THE BAY
AREA WILL GET LESS RAIN. THERE'S QUITE A BIT OF DISAGREEMENT
BETWEEN THE MODELS ON HOW MUCH LESS, WITH HIGH RESOLUTION GUIDANCE
MUCH DRIER THAN GLOBAL MODELS. OUTSIDE OF THE NORTH BAY WE COULD
GET ANYWHERE FROM LESS THAN 1/10" OR UP TO 3". THE ECMWF ENSEMBLE
SPREAD RANGES FROM 0.25" TO 2.5" AT SFO. THAT'S A SIGNIFICANT
AMOUNT OF UNCERTAINTY TO PUT IN THE SHORT TERM SECTION, BUT WITH
THE HEAVIER LINE OF SHOWERS EXPECTED TO STALL SOMEWHERE ALONG THE
COAST, IT MAKES SENSE. THE IQR IS MORE REASONABLE AT 1-1.5", BUT
THE OUTLIER MEMBERS ARE JUST AS LIKELY AS ANY OTHER SOLUTION IN
THE ENSEMBLE. CUT-OFF LOW PRESSURE SYSTEMS ARE HARD TO FORECAST
BECAUSE THERE IS NOTHING OBVIOUS MOVING THEM ALONG. IT'S LIKE A
TODDLER IN A CANDY STORE THAT JUST LET GO OF THEIR PARENT'S HAND.
NOBODY KNOWS WHAT WILL HAPPEN. THE EXACT TRACK OF THIS DRIFTING
FEATURE WILL HAVE A BIG INFLUENCE ON THE RAIN TOTALS TODAY. THE
SYSTEM SHOULD DRIFT SOMEWHERE NEAR THE COAST OF THE BAY AREA THIS
AFTERNOON BEFORE BECOMING VERTICALLY STACKED, DRIFTING SOUTH, AND
WEAKENING OVERNIGHT. THIS WILL COINCIDE WITH THE PASSAGE OF A
SHARP TROUGH IN THE JET STREAM, FLIPPING UPPER LEVEL WINDS NEARLY
180 DEGREES FROM SW TO NE. THAT CHANGES EVERYTHING FOR THE REST
OF THE WEEK.
LONG TERM
ISSUED AT 1203 AM PST MON JAN 5 2026
(TUESDAY THROUGH SUNDAY)
IN A WORD, DRY. AS THE UPPER LEVEL WINDS FLIP TO NORTHERLY
FOLLOWING PASSAGE OF THE TROUGH AXIS, DRIER, MORE STABLE AIR WILL
START TO MOVE IN. TUESDAY IS A TRANSITION DAY BETWEEN THE WET
STORMY PATTERN WE'VE HAD FOR THE LAST WEEK, AND MUCH DRIER WEATHER
THAT ARRIVES IN EARNEST WEDNESDAY. BEFORE WE GET THERE, DON'T BE
SURPRISED TO SEE A COUPLE SHOWERS ON TUESDAY, BUT NOTHING
COMPARABLE TO THE LAST FEW DAYS. THERE SHOULDN'T BE ANY MORE
FLOODING CONCERNS, ESPECIALLY AFTER THE SUN COMES UP. A WEAK
TROUGH WILL MOVE THROUGH ON WEDNESDAY, BUT SHOULDN'T BRING MORE
THAN CLOUDS. BY THURSDAY, A 500 MB RIDGE WILL BUILD AND THE SKIES
WILL CLEAR. THE PW WILL DROP BELOW 0.4" (25TH PERCENTILE), WHERE
IT COULD STAY FOR THE NEXT 2 WEEKS. THE CLEAR SKIES WILL BRING
COLD MORNING TEMPERATURES WITH INTERIOR AREAS DROPPING INTO THE
30S FOR THE FIRST TIME SINCE LATE DECEMBER. AN INSIDE SLIDER
PATTERN COULD DEVELOP AND WILL BRING SOME OFFSHORE WINDS THIS
WEEKEND BEFORE ANOTHER RIDGE BUILDS NEXT WEEK.
AVIATION
(12Z TAFS)
ISSUED AT 329 AM PST MON JAN 5 2026
VFR-MVFR WITH AREAS IFR IN INCREASING RAIN AND GUSTY SOUTHERLY
WINDS TODAY. RAIN BECOMING SHOWERY TONIGHT AND TUESDAY MORNING,
WINDS EASE TONIGHT.
VICINITY OF SFO...VFR-MVFR WITH RAIN AND INCREASINGLY GUSTY
SOUTH-SOUTHEASTERLY WINDS TODAY. RAIN BECOMING SHOWERY TONIGHT AND
TUESDAY MORNING, WINDS EASE TONIGHT.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR-MVFR WITH RAIN AND GUSTY
SOUTHEASTERLY WINDS TODAY. RAIN BECOMING SHOWERY TONIGHT AND
TUESDAY MORNING, WINDS EASE TONIGHT.
MARINE
(TODAY THROUGH SATURDAY)
ISSUED AT 323 AM PST MON JAN 5 2026
A LOW PRESSURE SYSTEM OVER THE COASTAL WATERS WILL RESULT IN RAIN,
A SLIGHT CHANCE OF THUNDERSTORMS, INCREASING SOUTH WINDS INCLUDING
SOUTHERLY GALES OVER THE SOUTHERN INNER COASTAL WATERS AND THE
MONTEREY BAY TODAY TO THIS EVENING. WINDS EASE LATE TONIGHT WHILE
SHOWERS CONTINUE TONIGHT AND TUESDAY MORNING. SEAS WILL REMAIN
MODERATE TO ROUGH TODAY TO THIS EVENING. LONG PERIOD NORTHWESTERLY
SWELL RETURNS LATER THIS WEEK.
BEACHES
ISSUED AT 1203 AM PST MON JAN 5 2026
ONE LAST DAY OF COASTAL FLOODING FROM KING TIDES AND STORM SURGE.
WHILE LOWER THAN PREVIOUS DAYS, THE HIGH TIDE WILL STILL BE
ROUGHLY 1.2 FEET ABOVE NORMAL, BRINGING MINOR IMPACTS TO LOW-LYING
AREAS NEAR SHORELINES AND TIDAL WATERWAYS DURING HIGH TIDE. THE
COASTAL FLOOD ADVISORY IS IN EFFECT THROUGH 3 PM TODAY FOR THE SAN
FRANCISCO BAY AND SAN PABLO BAY. HIGH TIDE IS EXPECTED IN SAN
FRANCISCO AT 12:08 PM MONDAY. HIGH TIDE TIMING VARIES UP TO 90
MINUTES LATER THROUGH THE SAN FRANCISCO BAY.
MTR WATCHES/WARNINGS/ADVISORIES
CA...COASTAL FLOOD ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR CAZ006-
506-508.
PZ...SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 3 PM PST THIS
AFTERNOON FOR SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY UNTIL 9 AM PST THIS MORNING FOR MRY BAY-
PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT PIEDRAS
BLANCAS 0-10 NM.
GALE WARNING FROM 9 AM THIS MORNING TO 9 PM PST THIS EVENING FOR
MRY BAY-PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR PT ARENA
TO PT REYES 0-10 NM-PT ARENA TO PT REYES 10-60 NM-PT REYES
TO PIGEON PT 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 9 PM PST THIS
EVENING FOR PIGEON PT TO PT PINOS 10-60 NM.
SHORT TERM...FLYNN
LONG TERM....FLYNN
AVIATION...CANEPA
MARINE...CANEPA
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