622
FXUS66 KMTR 152207
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
207 PM PST MON DEC 15 2025
..NEW SHORT TERM, LONG TERM
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.
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
(18Z TAFS)
ISSUED AT 1117 AM PST MON DEC 15 2025
IT WAS A FOGGY START TO THE MORNING ACROSS THE BAY AREA WITH FOG
LINGERING OVER THE MAJORITY OF THE SF BAY TERMINALS. CONFIDENCE IS
INCREASING THAT WE WILL SEE CLEARING ALONG THE BAY SHORELINE BY LATE
THIS MORNING AS CLOUD COVER STARTS TO BREAK UP OVER THE BAY.
STARTING TO SEE SOME IMPROVEMENTS IN VISIBILITY AS WELL WHICH
SUGGESTS FOG CHANCES ARE DIMINISHING. FOG IS LIKELY TO RETURN AGAIN
TONIGHT INTO TOMORROW MORNING BUT AN INCOMING WEAK SYSTEM MAY IMPACT
THE TIMING OF FOG RETURNING. CURRENT THINKING IS THAT WE WILL HAVE
ONE MORE NIGHT OF FOGGY CONDITIONS (MONDAY INTO TUESDAY) WITH THE
SYSTEM SET TO ARRIVE LATER IN THE DAY ON TUESDAY. KEPT THE OVERALL
TIMING SIMILAR TO PERSISTENCE BUT MADE SOME MINOR ADJUSTMENTS TO THE
ARRIVAL TIMING OF FOG.
VICINITY OF SFO...FOG/STRATUS IS CLEARING OVER THE NORTHERN PORTIONS
OF THE SF BAY WHICH HAS ALLOWED CONDITIONS TO IMPROVE DIRECTLY OVER
SFO. CONFIDENCE IS LOW TO MEDIUM ON THE RETURN OF STRATUS AND FOG
TONIGHT WITH CURRENT THINKING LEANING MORE TOWARDS STRATUS IMPACTING
SFO. LAMP GUIDANCE SHOWS INCREASING LIKELIHOOD OF STRATUS AFTER 08Z
WITH HIGHEST CONFIDENCE IN STRATUS RETURNING BY 09Z. FOR NOW, KEPT
IN LINE WITH MOS GUIDANCE SHOWING A SLIGHTLY EARLIER RETURN BY 06Z
BUT THIS MAY NEED TO BE PUSHED BACK DEPENDING ON HOW FAST STRATUS IS
ABLE TO RETURN TONIGHT. CONFIDENCE IS LOW THAT DENSE FOG WILL
DIRECTLY IMPACT SFO BUT SOME REDUCTION IN VISIBILITIES IS EXPECTED
OVERNIGHT. CONFIDENCE IS MODERATE THAT MVFR STRATUS WILL PERSIST FOR
MUCH OF TOMORROW AS A RESULT OF THE APPROACHING SYSTEM.
SFO BRIDGE APPROACH...LOCALIZED FOG/STRATUS IS EXPECTED WITHIN THE
SOUTHERN SAN FRANCISCO BAY ALONG THE BRIDGE APPROACH THROUGH EARLY
THIS AFTERNOON. FOG IS DISSIPATING MORE SLOWLY OVER THE BAY WITH
LOCALIZED DENSE FOG (1/4SM VIS) EXPECTED TO CONTINUE. SATELLITE
SHOWS THE FOG IS BEGINNING TO ERODE WHICH INCREASES CONFIDENCE THAT
THE BRIDGE APPROACH WILL SEE VAPS FOR AT LEAST SOME PORTION OF THE
AFTERNOON.
MONTEREY BAY TERMINALS...FOG HAS LARGELY DISSIPATED ACROSS THE
CENTRAL COAST WITH VISIBILITIES IMPROVING AND CLOUD COVER
DISSIPATING. LOW TO MODERATE CONFIDENCE IN THE RETURN OF FOG
TONIGHT. LEANED ON A MIXTURE OF PERSISTENCE AND LAMP GUIDANCE TO
PUSH THE RETURN OF LOWER VISIBILITIES BACK TONIGHT. WINDS GENERALLY
STAY LIGHT BUT A MORE MODERATE SEA BREEZE IS EXPECTED ALONG THE
COAST DURING THE AFTERNOON/EVENING HOURS.
MARINE
(TODAY THROUGH SATURDAY)
ISSUED AT 1117 AM PST MON DEC 15 2025
SOUTHERLY FLOW WILL PREVAIL NORTH OF PIGEON POINT AHEAD OF AN
APPROACHING FRONTAL SYSTEM. DENSE FOG CONTINUES ACROSS THE
MONTEREY BAY AND SAN FRANCISCO BAY. CONDITIONS ARE LIKELY TO
IMPROVE BY LATE THIS MORNING BUT PATCHY DENSE FOG IS LIKELY TO
PERSIST IN THE NORTHERN SAN FRANCISCO BAY AND WEST DELTA INTO THE
AFTERNOON. MODERATE TO FRESH WINDS CONTINUE ACROSS THE SOUTHERN
WATERS WITH PERIODS OF MODERATE WINDS EXPECTED ACROSS THE
NORTHERN WATERS. 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...KENNEDY
MARINE...KENNEDY
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