493
FXUS66 KMTR 160503
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
903 PM PST MON DEC 15 2025
..NEW UPDATE
KEY MESSAGES
UPDATED AT 343 AM PST MON DEC 15 2025
- WET WEATHER RETURNS LATE TODAY AND PERSISTS THROUGH THE WEEK
AND LIKELY INTO NEXT WEEK.
- CONFIDENCE IS INCREASING THAT IMPACTFUL WEATHER WILL ARRIVE FOR
NEXT WEEK'S HOLIDAY TRAVEL. CHECK BACK FOR UPDATES.
UPDATE
ISSUED AT 842 PM PST MON DEC 15 2025
THE PICTURE FROM SPACE SHOWS SOME HIGH CLOUDS PASSING OVER THE
REGION, WITH SOME POCKETS OF STRATUS AND FOG PEAKING THROUGH FOR
THE EAST BAY VALLEYS. FOR THE FIRST TIME IN THREE DAYS, THE
EVENING UPDATE DOES NOT INCLUDE A DENSE FOG ADVISORY! THIS MAY BE
SHORT LIVED AS VISIBILITY HAS STARTED TO DROP IN THE NORTH AND
EAST BAY VALLEYS THIS EVENING, BUT FOR NOW, IF YOU'RE TRAVELING
THIS EVENING, BE PREPARED FOR PATCHY FOG IN THESE AREAS. GIVEN HOW
FOGGY IT'S BEEN THE PAST FEW MORNINGS, CONSIDER CHECKING THE
FORECAST, WEATHER, AND TRAFFIC CONDITIONS BEFORE HEADING OUT
TOMORROW.
SHORT TERM
ISSUED AT 104 PM PST MON DEC 15 2025
(THIS EVENING THROUGH TUESDAY)
INTERESTING SETUP THIS AFTERNOON WEATHER WISE. NO REAL CHANGE FOR
THE CENTRAL VALLEY OR INTERIOR EAST BAY AS THEY STILL DEAL WITH
TULE FOG IMPACTS. NORTH BAY, SF BAY, AND THE SOUTH BAY ON THE
OTHER HAND ARE SEEING A WELCOMED SIGHT, THE SUN. SOME OF THESE
LOCALES STRUGGLED TO SEE THE SUN OVER THE WEEKEND KEEPING THEM
CHILLY. THAT BEING SAID, EVEN WITH SOME SUNSHINE THIS AFTERNOON
IT'S LATE IN THE DAY AND NOT MUCH DAYTIME HEATING LEFT. THEREFORE
UNDERSHOT THE FORECAST FROM THE NBM TODAY FOR MOST OF THE BAY
AREA, ESPECIALLY THE INTERIOR EAST BAY. CENTRAL COAST WILL BE THE
WARMEST OF THE BUNCH WITH A FEW SPOTS AIMING FOR THE LOWER 70S.
SO WHY THE CHANGE? LINGERING OFFSHORE FLOW OVER THE NORTH AND EAST
BAY COMBINED WITH A WEAK SYSTEM APPROACHING FROM THE NORTH.
LATEST SURFACE ANALYSIS SHOWS A WEAK COLD FRONT OFF THE FAR
NORCAL COAST MOVING S AND E. IN FACT, KMUX RADAR WAS SWITCHED TO
PRECIP FOR THE FIRST TIME IN A LONG TIME. A FEW SCOUT SHOWERS
AHEAD OF THE FRONT ARE BEING PICKED OFF THE NORTH BAY COAST THIS
AFTERNOON.
FOR TONIGHT: DO HAVE SHOWERS RETURNING TO THE NORTH BAY
OVERNIGHT. NOT EXPECTING A BIG PRECIP EVENT TONIGHT, BUT MORE OF A
BRUSH BY FROM A PASSING BOUNDARY. CURRENT FORECAST DOESN'T HAVE
PRECIP SOUTH OF THE GOLDEN GATE. IF WE DO ACTUALLY GET SOME BUCKET
TIPS FROM RAIN THIS WILL BE THE FIRST PRECIP OF THE MONTH FOR THE
REGION. IN OTHER WORDS, IT'S BEEN DRY LATELY. ONE IMPACT THAT
WON'T GO AWAY TONIGHT WILL BE LOW CLOUDS AND FOG, ESPECIALLY EAST
BAY AND WEST DELTA. GIVEN THE APPROACHING FRONT AND INCREASED
CLOUD COVER NOT EXPECTING WIDESPREAD DENSE FOG LIKE THIS MORNING,
BUT PATCHY DENSE FOG IS MORE LIKELY.
FOR TUESDAY; SHOWERS FINALLY MAKE IT SOUTH OF THE GOLDEN GATE BY
THE AFTERNOON WITH MINOR IMPACTS TO THE EVENING COMMUTE. ONCE
AGAIN, NOT EXPECTING A WASH OUT, BUT BENEFICIAL PRECIP
NONETHELESS.
LONG TERM
ISSUED AT 202 PM PST MON DEC 15 2025
(TUESDAY NIGHT THROUGH NEXT SUNDAY)
SHOWERS WILL LINGER THROUGH WEDNESDAY AS THE WEAK BOUNDARY
TRAVERSES THE REGION. SHOWERS WILL BE MOST PREVALENT ACROSS THE
NORTH BAY. RAINFALL AMOUNTS WITH THIS FIRST PUSH OF PRECIP WILL
GENERALLY BE A TENTH TO A HALF FOR THE NORTH BAY AND A FEW
HUNDREDTHS ELSEWHERE. INTERIOR AREAS OF THE CENTRAL COAST WILL
LIKELY NOT SEE ANY PRECIP WITH THIS SYSTEM.
WE'LL GET A BRIEF PAUSE/BREAK IN WIDESPREAD PRECIP LATE WEDNESDAY
EVENING AND THURSDAY BEFORE THE ATMOSPHERE RELOADS WITH ANOTHER
SYSTEM. IF THERE ARE A FEW LINGERING SHOWERS THEY'LL BE ACROSS THE
NORTH BAY.
THE ATMOSPHERIC "RELOAD" WILL COME IN THE WAY OF A LOW SPINNING
UP OVER THE PACIFIC NORTH OF HI AND ANOTHER STORM SYSTEM SWINGING
INTO THE PACNW. THIS SET UP WILL ALLOW FOR A MOISTURE PLUME TO
TAKE AIM AT THE PACNW BEFORE SLIDING DOWN THE NORCAL COAST ON
FRIDAY. WIDESPREAD RAIN RETURNS INITIALLY TO THE NORTH BAY FRIDAY
AFTERNOON BEFORE PUSHING SOUTH TO THE CENTRAL COAST ON SATURDAY.
BY SUNDAY THE NEWLY FORMED LOW OVER THE PACIFIC WILL MOVE TOWARD
THE NORCAL, WHICH WILL BRING A REINFORCING SHOT OF HIGHER PWAT
AIR TO THE REGION. AS A RESULT, EXPECT ANOTHER UPTICK IN RAIN
SHOWER ACTIVITY, COVERAGE, AND INTENSITY. THIS PUSH OF MOISTURE
WILL KEEP PRECIP IN THE PICTURE MONDAY AND EVEN INTO TUESDAY. A
GREAT WAY TO DESCRIBE THE OVERALL WEATHER STARTING FRIDAY THROUGH
EARLY NEXT WEEK WILL BE EPISODES OR PERIODS OF RAIN. NOT A
COMPLETE WASHOUT, BUT MEASURABLE RAIN. INITIAL RAINFALL
PROJECTIONS THURSDAY THROUGH MONDAY: NORTH BAY AND COASTAL MTS
2-5", BAY AREA AND MONTEREY BAY REGION 1-2", INTERIOR CENTRAL
COAST LESS THAN 1". PERIOD OF HEAVIEST RAINFALL LOOKS TO BE
SUNDAY INTO MONDAY.
LOTS OF FOCUS FOR THE EXTENDED, AND RIGHTFULLY SO AS HOLIDAY
TRAVEL AND HOLIDAY PLANS COME INTO PLAY. CONFIDENCE CONTINUES TO
INCREASE THAT IMPACTFUL WEATHER WILL RETURN TO THE REGION
BEGINNING AROUND DEC 22 AND CONTINUING THROUGH THE HOLIDAY. CPC
CONTINUES TO HIGHLIGHT A LARGE PORTION OF NORCAL FOR EXCESSIVE
RAINFALL. LONGER RANGE ENSEMBLES SHOW POTENTIAL AS WELL, BUT THIS
FAR OUT IT'S ALL ABOUT THE DETAILS - AMOUNTS, CONFIDENCE,
TIMING, IMPACTS. THOSE WILL BE SORTED OUT IN THE DAYS TO COME.
PLEASE CHECK BACK FOR UPDATES AND MORE DETAILS.
AVIATION
(00Z TAFS)
ISSUED AT 330 PM PST MON DEC 15 2025
FOG AND STRATUS HAVE DISSIPATED ACROSS MOST OF THE BAY AREA WITH THE
ONLY REGIONS REMAINING SOCKED IN BEING THE FAR INLAND LOCATIONS
LYING WITHIN THE CENTRAL VALLEY EAST OF CCR, LVK, AND THE DIABLO
RANGE. MID- TO HIGH-LEVEL CLOUDS ARE FILTERING INTO THE REGION IN
ADVANCE OF A SYSTEM THAT WILL BRING CHANCES FOR LIGHT SHOWERS
TONIGHT INTO TUESDAY FOR THE NORTH BAY. HAVE OPTED TO MAINTAIN THE
PREVIOUS FORECAST FOR WIDESPREAD STRATUS WITH SOME COASTAL AND
VALLEY FOG DEVELOPING TONIGHT, BUT WITH THE INCOMING SYSTEM BRINGING
EXTENSIVE CLOUD COVER, LOW CONFIDENCE IN THE CLEARING TIMES ON
TUESDAY MORNING, WHICH GENERALLY COME FROM A PERSISTENCE FORECAST.
WINDS WILL BE LIGHT AND GENTLE ACROSS THE REGION WITH A SLIGHT
ONSHORE IMPULSE IN THE COASTAL REGION THROUGH THE EVENING HOURS,
OTHERWISE OFFSHORE. LIGHT AND TERRAIN-DRIVEN WINDS PREVAIL OVERNIGHT
BEFORE A LIGHT TO GENTLE ONSHORE PULSE RESUMES TUESDAY.
VICINITY OF SFO... VFR WITH MID- TO HIGH LEVEL CLOUDS THROUGH THE
EVENING. LATEST MODEL OUTPUT DEPICTS MVFR STRATUS FLOWING IN CLOSER
TO THE 06-07Z TIMEFRAME, WHICH FITS WITH THE PREVIOUS TAF FORECAST.
LOW CONFIDENCE THAT DENSE FOG DIRECTLY IMPACTS THE TERMINAL, BUT
SOME REDUCTION IN VISIBILITY IS EXPECTED OVERNIGHT. AFTERWARDS,
MODERATE CONFIDENCE THAT THE STRATUS PERSISTS THROUGH THE REST OF
THE TAF PERIOD. WINDS WILL REMAIN LIGHT TO GENTLE THROUGHOUT THE
FORECAST PERIOD, WITH OFFSHORE FLOWS AT PRESENT TURNING LIGHT AND
WEST-NORTHWEST BY TUESDAY. LOW TO MODERATE CONFIDENCE OF SHOWERS
DEVELOPING AT THE TERMINAL BY TUESDAY EVENING.
SFO BRIDGE APPROACH... LOCALIZED STRATUS AND POTENTIAL FOR DENSE FOG
IS EXPECTED TONIGHT THROUGH TUESDAY MORNING ACROSS THE SOUTHERN SAN
FRANCISCO BAY. OTHERWISE, SIMILAR TO SFO.
MONTEREY BAY TERMINALS... VFR WITH LIGHT TO GENTLE NORTHWEST BREEZES
THROUGH THE EARLY EVENING HOURS. LOW TO MODERATE CONFIDENCE THAT
STRATUS AND FOG RETURN TONIGHT, WITH THE LATEST MODEL OUTPUT SHOWING
THE STRATUS DECK APPROACHING THE COAST, BUT NOT REACHING IT UNTIL
CLOSE TO THE END OF THE TAF PERIOD. HAVE OPTED TO LEAVE THE CURRENT
FORECAST IN PLACE AND BASE THE CLEARING TIMES ON PERSISTENCE, BUT
WILL MONITOR STRATUS EVOLUTION THROUGH THE EVENING IN CASE
CONFIDENCE IN THE RETURN OF STRATUS INCREASES. LIGHT DRAINAGE FLOWS
OVERNIGHT BEFORE LIGHT TO GENTLE NORTHWEST WINDS RESUME ON
TUESDAY.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 842 PM PST MON DEC 15 2025
SOUTHERLY FLOW WILL PREVAIL NORTH OF PIGEON POINT AHEAD OF AN
APPROACHING FRONTAL SYSTEM. MODERATE TO FRESH WINDS CONTINUE
ACROSS THE SOUTHERN WATERS WITH PERIODS OF MODERATE WINDS
EXPECTED ACROSS THE NORTHERN WATERS. PATCHY DENSE FOG PERSISTS
WITHIN THE WEST DELTA, AND EXPANDS ACROSS THE BAYS AND THE COASTAL
WATERS TONIGHT INTO TUESDAY MORNING. A WEAK SYSTEM WILL BRING
MODERATE LONG PERIOD NORTHWEST SWELL TUESDAY INTO THE WEEKEND.
MODERATE SEAS RETURN WITH WAVE HEIGHTS BUILDING UP TO 9 FEET.
RAIN CHANCES INCREASE LATE TONIGHT AND REMAIN ELEVATED THROUGH
THE END OF THE FORECAST PERIOD.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 9 PM PST TUESDAY FOR PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...DIALH
MARINE...KR
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