600
FXUS66 KMTR 141107
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
307 AM PST SUN DEC 14 2025
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1202 AM PST SUN DEC 14 2025
- DENSE FOG THIS MORNING ACROSS THE NORTH BAY VALLEYS AND EAST
BAY INTERIOR VALLEYS.
- BENEFICIAL RAIN EXPECTED THIS WEEK.
- HEAVIER RAIN AND STRONG WIND POSSIBLE NEXT WEEK.
SHORT TERM
ISSUED AT 1202 AM PST SUN DEC 14 2025
(TODAY AND TONIGHT)
WE ARE NOW ON THE BACKSIDE OF THE 500 MB RIDGE THAT DOMINATED THE
WEATHER FOR THE LAST COUPLE WEEKS. A SHORT WAVE TROUGH IS FURTHER
WEAKENING THE LONG WAVE RIDGING. THIS FEATURE BROUGHT A STRONG
SOUTHERLY SURGE OF STRATUS ON SATURDAY, BUT WASN'T ENOUGH TO MIX
OUT THE RADIATION FOG ACROSS THE VALLEYS. SO NOW WE HAVE BOTH
COASTAL STRATUS AND INLAND VALLEY FOG. BOUNDARY LAYER AVERAGED WINDS
HAVE SHIFTED FROM EASTERLY TO SOUTHERLY OVER THE LAST 24 HOURS,
BUT REMAIN WEAK AT THE SURFACE. DENSE FOG IS BEING REPORTED ACROSS
THE NORTH BAY VALLEYS AND INTERIOR EAST BAY VALLEYS. THIS FOG WILL
PERSIST THROUGH LATE MORNING BEFORE CLEARING, AND A DENSE FOG
ADVISORY IS IN EFFECT UNTIL 11 AM. AFTERNOON TEMPERATURES WILL BE
COOLER THAN THEY HAVE BEEN WITH MORE CLOUD COVERAGE AND DROPPING
850 MB TEMPS. BOTH THE LONG WAVE RIDGE AND SHORT WAVE TROUGH WILL
CONTINUE TO SLIDE EAST THROUGH THE DAY. THERE IS ANOTHER GOOD
CHANCE FOR FOG IMPACTS SUNDAY NIGHT AS THE LOWER ATMOSPHERE
REMAINS POORLY MIXED.
LONG TERM
ISSUED AT 1202 AM PST SUN DEC 14 2025
(MONDAY THROUGH SATURDAY)
500 MB ZONAL FLOW WITH A TIGHTER PRESSURE GRADIENT WILL MOVE IN BY
TUESDAY AND PERSIST THROUGH THE WEEK. AS THIS NEW PATTERN LINES UP
WITH HIGHER MOISTURE IT WILL SUPPORT A FEW ROUNDS OF LIGHT RAIN.
WITHOUT A DEEP TROUGH THERE IS NO REAL THREAT OF HEAVY RAIN THIS
WEEK. HIGH CLOUDS ON MONDAY WILL WARN OF THE APPROACHING RAIN,
WITH THE FIRST ROUND EXPECTED TUESDAY THROUGH WEDNESDAY. THE
CURRENT FORECAST HAS BEEN PRETTY CONSISTENT WITH AROUND 1/4" IN
THE NORTH BAY AND LESS THAN 1/10" EVERYWHERE ELSE. WHILE THE ZONAL
FLOW WILL PERSIST, DRIER AIR WILL MOVE IN THURSDAY LIKELY
BRINGING A BREAK IN THE RAIN. THE NEXT ROUND WILL MOVE IN FRIDAY
AND PERSIST THROUGH THE WEEKEND. BEYOND NEXT WEEKEND THERE IS A
LOT OF UNCERTAINTY IN THE DETAILS, BUT THE ENSEMBLE CLUSTER
ANALYSIS REVEALS GOOD AGREEMENT IN THE OVERALL PATTERN EVOLVING TO
FEATURE DEEP TROUGHING JUST OFF THE COAST. THIS COULD SUPPORT AN
ATMOSPHERIC RIVER EARLY NEXT WEEK IF THE MOISTURE PLUME LINES UP
RIGHT. THE CLIMATE PREDICTION CENTER CONTINUES TO SHOW A MODERATE
RISK FOR BOTH STRONG WINDS AND HEAVY RAIN FROM 12/20-12/26.
AVIATION
(12Z TAFS)
ISSUED AT 307 AM PST SUN DEC 14 2025
FOG AND STRATUS /LIFR-IFR-MVFR/ CONTINUE TO FILL IN ACROSS THE
FORECAST AREA. CLEARING WILL BE SLOW TODAY WITH MIX OUT TIMES IN
THE LATE MORNING TO EARLY AFTERNOON. FOG AND STRATUS REDEVELOP
TONIGHT AND MONDAY MORNING.
VICINITY OF SFO...IFR MIXING OUT TO VFR BY NOON, MVFR-IFR
REDEVELOPS TONIGHT AND MONDAY MORNING. MAINLY LIGHT NORTHEAST TO
NORTH WIND.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...STRATUS /IFR-MVFR/ MIXING OUT TO VFR BY
NOON. STRATUS REDEVELOPS TONIGHT AND MONDAY MORNING.
MARINE
(TODAY THROUGH FRIDAY)
ISSUED AT 301 AM PST SUN DEC 14 2025
A GENTLE TO MODERATE BREEZE CONTINUES ACROSS THE COASTAL WATERS
TODAY. WINDS INCREASE TO MODERATE TO FRESH ACROSS THE SOUTHERN
COASTAL WATERS MONDAY AS THE FIRST IN A SERIES OF WEAK SYSTEMS
REACHES THE COASTAL WATERS. RAIN CHANCES INCREASE THIS WEEK. LOW
SEAS PERSIST THROUGH THE REMAINDER OF THE WEEKEND BEFORE BUILDING
TO MODERATE TO ROUGH BY MID WEEK.
MTR WATCHES/WARNINGS/ADVISORIES
CA...DENSE FOG ADVISORY UNTIL 11 AM PST THIS MORNING FOR CAZ506-510.
PZ...SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PST MONDAY FOR PT PINOS
TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...FLYNN
LONG TERM....FLYNN
AVIATION...CANEPA
MARINE...CANEPA
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