946
FXUS66 KMTR 241837
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1137 AM PDT FRI OCT 24 2025
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1229 AM PDT FRI OCT 24 2025
- PATCHY MORNING FOG WITH SEASONAL WEATHER THIS AFTERNOON
- BENEFICIAL RAIN ACROSS THE BAY AREA ARRIVES SATURDAY
- LARGE SWELL HAS RETURNED WITH HAZARDOUS BEACH CONDITIONS
THROUGH THE WEEKEND
UPDATE
ISSUED AT 813 AM PDT FRI OCT 24 2025
A DENSE FOG ADVISORY REMAINS IN EFFECT UNTIL 10 AM THIS MORNING WITH
VISIBILITIES LESS THAN OR EQUAL TO 1/4 SM IN THE SONOMA VALLEY,
PETALUMA VALLEY AND OTHER VALLEY LOCATIONS AROUND THE NORTH BAY.
THERE IS PATCHY TO AREAS OF DENSE FOG AROUND THE MONTEREY BAY
REGION, SALINAS VALLEY, AND HOLLISTER VALLEY AS WELL. THESE
CONDITIONS SHOULD BEGIN TO IMPROVE THROUGHOUT THE MORNING AS SURFACE
TEMPERATURES WARM AND SKY CONDITIONS BEGIN TO CLEAR OUT. HIGH
CLOUDS ARE CURRENTLY MOVING INTO THE NORTH BAY AT THIS HOUR, THAT
MAY LIMIT DAYTIME HEATING, THUS EXTENDING THE TIME THAT FOG
DISSIPATES. OTHERWISE, NO UPDATES ARE ANTICIPATED THIS MORNING.
RGASS
SHORT TERM
ISSUED AT 1229 AM PDT FRI OCT 24 2025
(TODAY AND TONIGHT)
STRATUS IS FILLING IN A SHALLOW MARINE LAYER. AS THE SURFACE
TEMPERATURE CONTINUES TO DROP THROUGH THE EARLY MORNING THERE IS A
30-50% CHANCE FOR FOG TO DEVELOP ALONG THE COAST AND IN THE
VALLEYS. THE HIGH CLOUDS ASSOCIATED WITH SATURDAY'S COLD FRONT ARE
STILL TOO FAR AWAY TO LIMIT RADIATIONAL COOLING TONIGHT. FAVORABLE
CONDITIONS INCLUDE DEW POINTS HIGHER THAN SST, A 13-HOUR LONG
NIGHT, LIGHT WINDS, AND HIGH PRESSURE ALOFT. THIS COMBINATION
SHOULD SUPPORT A COMBINATION OF ADVECTION AND RADIATION FOG. IT'S
NOT A SLAM DUNK, HOWEVER. THE AIR TEMPERATURE IS ALREADY COOLER
THAN THE SST, WHICH CUTS OFF THE MAIN COOLING MECHANISM THAT
CAUSES SATURATION OVER WATER. THE BEST CHANCE IS IN THE COUPLE
HOURS BEFORE OR AFTER SUNRISE, WHICH WOULD OBVIOUSLY IMPACT THE
MORNING COMMUTE. ANY FOG THAT FORMS SHOULD CLEAR BY 10 AM.
OTHERWISE TODAY WILL BE SIMILAR TO YESTERDAY, ALBEIT WITH MORE
HIGH CLOUD COVER SIGNALING THE APPROACHING COLD FRONT. THESE
CLOUDS WILL LIMIT DAYTIME HEATING BY A COUPLE DEGREES, BUT SHOULD
LEAD TO A KILLER SUNSET IF YOU CAN AVOID THE RETURNING MARINE
LAYER STRATUS THIS EVENING.
LONG TERM
ISSUED AT 1229 AM PDT FRI OCT 24 2025
(SATURDAY THROUGH THURSDAY)
PREFRONTAL RAIN WILL BEGIN EARLY SATURDAY MORNING IN THE NORTH
BAY. THE MAIN BAND OF RAIN SHOULD REACH SANTA ROSA AROUND 3 AM,
SAN FRANCISCO BY 5 AM, AND SAN JOSE BY 7 AM. HIGH RESOLUTION
MODELS ARE SHOWING MUCH LESS RAIN THAN PREVIOUSLY EXPECTED, AND
OUR OFFICIAL FORECAST CONTINUES TO TREND IN THAT DIRECTION. THE
06Z HRRR JUMPS OUT WITH LESS THAN 1/10" ACROSS THE BAY AREA AND
HARDLY ANYTHING ACROSS THE INLAND EAST BAY AND SOUTH BAY. THERE
LOOKS TO BE A DISTINCT BREAK SATURDAY NIGHT BEFORE RAIN RETURNS
SUNDAY, THOUGH ONLY ABOUT HALF AS MUCH AS SATURDAY. THE LIGHTNING
THREAT IS MINUSCULE DUE MAINLY TO SHALLOW LAPSE RATES. THE
MOISTURE, SHEAR, AND TRIGGER (COLD FRONT) ARE ALL THERE HOWEVER,
SO IT'S STILL WORTH KEEPING AN EYE ON CONVECTION FOR ANY LOW-
TOPPED ROTATING CELLS. COLDER AIR WILL ACCOMPANY THE FRONT, WITH
THE 850 TEMPERATURE DROPPING TO 7 OR 8C, WHICH IS SOMEWHERE
BETWEEN THE 10TH AND 25TH PERCENTILE FOR THIS TIME OF YEAR.
NOTHING CRAZY, BUT SUNDAY AND MONDAY MORNING WILL FEEL CHILLY AS A
RESULT. THE SURFACE WIND SPEED DOESN'T LOOK VERY HIGH WITH THIS
SYSTEM, BUT THE DIRECTION WILL GRADUALLY SHIFT TO SW AS THE FRONT
APPROACHES. WINDS WILL FLIP BACK TO NW AS THE FRONT MOVES
THROUGH.
AFTER THE POST FRONTAL SHOWERS CLEAR UP MONDAY MORNING, PERIODS OF
ZONAL FLOW AND WEAK RIDGING WILL BRING DRIER AND MORE SEASONAL
CONDITIONS FOR THE MAJORITY OF NEXT WEEK. HALLOWEEN STILL LOOKS
GOOD ON FRIDAY. THERE'S SOME INDICATION THAT THE NEXT SYSTEM COULD
ARRIVE NEXT WEEKEND, BUT ROUGHLY 70% OF ENSEMBLE MEMBERS KEEP A
RIDGING PATTERN.
AVIATION
(18Z TAFS)
ISSUED AT 1137 AM PDT FRI OCT 24 2025
AREAS OF FOG AND LOW CLOUDS /LIFR-IFR/ ARE STEADILY MIXING OUT,
OTHERWISE IT'S VFR. A RECENTLY DEPOSITED COOLER AIR MASS BLENDED
WITH HIGHER DEWPOINT AIR (WATER VAPOR), NOCTURNAL COOLING, ETC.
LEAD TO FOG AND LOW CLOUDS OVERNIGHT AND THIS MORNING. RESIDUAL
AIR MASS CHARACTERISTICS AND/OR ADDITIONAL COOLER AIR TO OUR WEST
WILL BECOME NUDGED EASTWARD AND INLAND SETTING US UP FOR AT LEAST
PATCHY FOG AND LOW CLOUDS /LIFR-IFR/ REDEVELOPING TONIGHT. A COOL
FRONTAL SYSTEM FROM THE NORTHWEST WILL BLEND IN WITH A MIX OF LIGHT
RAIN, FOG AND LOW CLOUDS /LIFR-IFR/ BEGINNING EARLY SATURDAY.
LATEST MODEL OUTPUT SHOWS THE COOL FRONTAL SYSTEM MOVING EAST-
SOUTHEAST ACROSS THE FORECAST AREA SATURDAY.
VICINITY OF SFO...DIURNAL SURFACE HEATING AND MIXING ARE HELPING
TO STEADILY IMPROVE CEILING CONDITION FROM BKN TO SCT THROUGH LATE
MORNING. LOWER LEVEL COOL AIR ADVECTION HAS DEEPENED ALLOWING
COASTAL LOW CLOUDS TO APPROACH FROM THE WEST-NORTHWEST OTHERWISE
STILL UNDER A FAIR AMOUNT OF MIXING FOR VFR TO PREVAIL DURING THE
AFTERNOON. POST SUNSET MVFR CEILING BECOMES INCREASINGLY LIKELY
ESPECIALLY BY EARLY SATURDAY WITH THE APPROACHING COOL FRONT FROM
THE NORTHWEST. LIGHT RAIN 15Z-17Z SATURDAY WITH POST FRONTAL
SHOWERS POSSIBLE THEREAFTER THOUGH MUCH MORE ISOLATED BY LATE
MORNING AND AFTERNOON SATURDAY. MAINLY ONSHORE WINDS 10 TO 15
KNOTS DURING THE 18Z TAF.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...COOL AIR DRAINAGE WINDS FROM THE SALINAS
VALLEY PLUS AREAS OF LOW VISIBILITY IN FOG HAVE NOW YIELDED TO
DIURNAL SURFACE HEATING AND MIXING, STEADILY IMPROVING CONDITIONS
EVERYWHERE CLOSER TO VFR. AIR MASS CHARACTERISTICS ARE SIMILAR
TONIGHT WITH A POTENTIAL FOR AT LEAST PATCHY FOG AND LOW CLOUDS
/LIFR-IFR/ REDEVELOPING. 12Z GUIDANCE FOR KWVI, KSNS AND KMRY TODAY
ALL LEAN TOWARD FOG REDEVELOPMENT TONIGHT AND SATURDAY MORNING.
AS THE COOL FRONT APPROACHES FROM THE NORTHWEST EARLY SATURDAY,
IT'S PROBABLY BEST TO PLAN ON LIGHT RAIN BLENDING IN WITH ALREADY
LOWERED IFR CONDITIONS IN FOG AND LOW CLOUDS IN THE MORNING. WINDS
SLOWLY BECOMING LIGHT ONSHORE TODAY, SHIFTING TO LIGHT COOL AIR
DRAINAGE WINDS TONIGHT AND SATURDAY MORNING AHEAD OF THE COOL
FRONTAL SYSTEM.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 1051 AM PDT FRI OCT 24 2025
AN ACTIVE, WET WEATHER PATTERN REACHING THE PACIFIC NORTHWEST
WILL PERIODICALLY SEND FRONTAL SYSTEMS AND WET WEATHER AS FAR
SOUTH AS THE BAY AREA DURING THE WEEKEND AND EARLY NEXT WEEK.
ROUGH SEAS WILL PREVAIL ACROSS THE WATERS THROUGH THIS WEEKEND.
EXPECT LONG PERIOD NORTHWESTERLY SWELL TODAY AND MODERATE PERIOD
SWELL TONIGHT THROUGH LATE SUNDAY NIGHT.
BEACHES
ISSUED AT 1052 AM PDT FRI OCT 24 2025
A MODERATE TO LONG PERIOD NORTHWESTERLY SWELL IS BUILDING ACROSS
THE COAST, CAUSING BREAKING WAVES OF 15 TO 20 FEET, WITH THE
HIGHEST WAVES UP TO 25 FEET IN FAVORED LOCATIONS. THIS WILL CAUSE
AN INCREASED RISK FOR SNEAKER WAVES AND RIP CURRENTS THROUGH LATE
SUNDAY NIGHT. SNEAKER WAVES CAN UNEXPECTEDLY RUN SIGNIFICANTLY
FARTHER UP THE BEACH THAN NORMAL, INCLUDING OVER ROCKS AND
JETTIES. RIP CURRENTS ARE TYPICALLY MORE FREQUENT AND STRONGER IN
THE VICINITY OF JETTIES, INLETS, AND PIERS. SWIMMERS SHOULD ALWAYS
SWIM NEAR A LIFEGUARD. REMAIN OUT OF THE WATER TO AVOID HAZARDOUS
SWIMMING CONDITIONS AND NEVER TURN YOUR BACK ON THE OCEAN!
MTR WATCHES/WARNINGS/ADVISORIES
CA...BEACH HAZARDS STATEMENT THROUGH LATE SUNDAY NIGHT FOR CAZ006-505-
509-529-530.
PZ...SMALL CRAFT ADVISORY FROM 3 AM TO 9 PM PDT SATURDAY FOR SF BAY N
OF BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 9 AM PDT SATURDAY
FOR PT ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR PT PINOS TO
PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM PDT SATURDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SMALL CRAFT ADVISORY UNTIL 9 AM PDT SATURDAY FOR PIGEON PT TO PT
PINOS 10-60 NM.
SHORT TERM...FLYNN
LONG TERM....FLYNN
AVIATION...CANEPA
MARINE...CANEPA
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