413
FXUS66 KMTR 121757
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1057 AM PDT TUE AUG 12 2025
..NEW AVIATION
KEY MESSAGES
UPDATED AT 320 AM PDT TUE AUG 12 2025
- MODERATE HEATRISK TODAY FOR PORTIONS OF INTERIOR MONTEREY AND SAN
BENITO COUNTIES.
- ELEVATED FIRE WEATHER CONCERNS PERSIST THROUGH WEDNESDAY FOR THE
INTERIOR CENTRAL COAST.
- PATTERN CHANGE TODAY, WITH MORE WIDESPREAD COOLING AND COASTAL
CLOUDS AND DRIZZLE STARTING WEDNESDAY.
UPDATE
ISSUED AT 935 AM PDT TUE AUG 12 2025
IT'S AUGUST SO OF COURSE WE'RE TALKING ABOUT FOGUST. AS NOTED
BELOW, THE MARINE LAYER IS PRETTY SOLID THIS MORNING WITH GREAT
INLAND PENETRATION. OVER THE LAST HOUR WE'RE FINALLY BEGINNING TO
SEE SOME THINNING ON THE EDGES. THIS THINNING OR GRADUAL CLEARING
WILL PERSIST THROUGH LATE MORNING. WHILE INLAND AREAS WILL SEE
SOME SUN, THE COASTAL AREAS HANG ONTO THE CLOUDS TODAY.
IF YOU HAPPENED TO VIEW THE SATELLITE IMAGERY THIS MORNING YOU'LL
NOTICE A FEW HIGHER LEVEL CLOUDS WEST OF PT CONCEPTION. THIS
CLUSTER OF CLOUDS ARE ASSOCIATED WITH A POCKET OF MOISTURE FROM
THE DECAYED TS IVO. SO THE BIG QUESTION OVER THE LAST FEW DAYS AND
THIS MORNING HAS BEEN, WHAT HAPPENS TO THE MOISTURE. DO WE GET
SHOWERS, THUNDERSTORMS, VIRGA, OR NOTHING? BASED ON SATELLITE
TRENDS, UPSTREAM NUCAPS SOUNDINGS, CAMS NWP, AND EXPERIENCE FEEL
COMFORTABLE WITH NOT RULING OUT A PASSING SHOWER OR TWO. THERE ARE
DEFINITELY INGREDIENTS TO BE CONCERNED WITH, BUT NOT ALL LINE UP
IN THE RIGHT SPOT OR OVERLAP TIMEWISE. WOULD LIKE TO SEE SOME
BETTER LIFT/INSTABILITY THROUGH THE LAYER OF MOISTURE ALOFT.
WOULD ALSO LIKE TO SEE MOISTURE TRACK FARTHER NORTH. A TROUGH TO
THE NORTH WILL BLOCK SOME OF THE MOISTURE TRANSPORT FLOW AS SEEN
BY GUIDANCE SHOWING MORE ZONAL AND LESS MERIDIONAL FLOW. ALL THAT
BEING SAID, THINK PASSING SHOWERS OR VIRGA SHOWER WILL BE
POSSIBLE LATE TONIGHT AND WEDNESDAY OVER THE CENTRAL COAST INTO
THE BAY AREA. NOT ENOUGH CONFIDENCE TO ADD SHOWERS TO THE FORECAST
JUST YET. WILL FINE TO THIS THINKING WITH THE AFTERNOON FORECAST
PACKAGE.
MM
SHORT TERM
ISSUED AT 320 AM PDT TUE AUG 12 2025
(TODAY AND TONIGHT)
IT'S FINALLY HAPPENING! THE PATTERN CHANGE BEGINS TODAY. FIRST UP,
IT WOULDN'T BE A NIGHT SHIFT DISCUSSION THIS WEEK WITHOUT
MENTIONING IT, THE STATUS OF THE STRATUS! SATELLITE IMAGERY SHOWS
STRATUS BLOSSOMING ACROSS A GOOD PORTION OF THE REGION INCLUDING
INTERIOR VALLEYS OF THE BAY AREA. THIS MATCHES THE MARINE LAYER
FOOT PRINT OF 1200-1500FT. EXPECT TO SEE THE SPREAD CONTINUE FOR
THE NEXT FEW HOURS WITH STRATUS GRADUALLY STARTING TO MIX OUT
AFTER SUNRISE. MUCH LIKE YESTERDAY, LOOK FOR MOSTLY SUNNY SKIES
FOR INTERIOR LOCATIONS AND FOR CLOUDS TO HANG AROUND THE COAST.
HIGH TEMPERATURES FOR MOST LOCATIONS WILL BE A FEW DEGREES COOLER,
WITH INTERIOR BAY AREA COUNTIES AND SANTA CRUZ COUNTY SEEING
HIGHS IN THE LOW 80S TO MID 90S COMPARED TO THE MID 80S TO NEAR
105 DEGREES FOR INTERIOR MONTEREY AND SAN BENITO. CLOSER TO THE
COAST, WHERE NATURE'S AC HOLDS, HIGHS WILL BE CLOSER TO THE MID
50S TO LOW 70S.
LONG TERM
ISSUED AT 320 AM PDT TUE AUG 12 2025
(WEDNESDAY THROUGH MONDAY)
NO MAJOR CHANGES FROM THE PREVIOUS LONG TERM FORECAST. REMNANT
MOISTURE FROM FORMER (IT IS NO LONGER A NAMED STORM) POST-TROPICAL
CYCLONE IVO REMAINS OF INTEREST. CURRENTLY ON SATURDAY YOU CAN
SEE THIS BEING PULLED NORTH ON SATELLITE IMAGERY THIS TUESDAY
MORNING. GUIDANCE REMAINS FAIRLY LACK LUSTER THANKS TO AN UPPER
LEVEL TROUGH SWING INTO THE PACNW WHICH SHOULD LIMIT THE LIFTING
MECHANISM NEEDED FOR SHOWER OR THUNDERSTORM DEVELOPMENT. SHOULD
THIS ARRIVAL BE DELAYED OR BE A BIT MORE TO OUR NORTH, THERE MAY
BE MORE ROOM FOR CONVECTIVE DEVELOPMENT AS THERE IS SOME CAPE,
REASONABLE MOISTURE, AND DECENT LAPSE RATES. LIKE WE SAW ON MONDAY
AFTERNOON, THERE ARE A FEW CAMS THAT TRY TO GENERATE ISOLATED
SHOWERS OVER THE REGION. BUT FOR NOW, WE'RE NOT EXPECTING ANYTHING
IN THE WAY OF PRECIPITATION. OUTSIDE OF THAT WE CAN LOOK FORWARD
TO THE COOLING TREND AND COASTAL STRATUS AND DRIZZLE LASTING INTO
THE WEEKEND.
AVIATION
(18Z TAFS)
ISSUED AT 1055 AM PDT TUE AUG 12 2025
MIX BAG OF IFR/MVFR CONDITIONS LINGERING THIS MORNING ACROSS MUCH OF
THE REGION, ESPECIALLY IN PLACES CLOSE TO THE BAYS AND THE COAST.
IMPROVING CONDITIONS ARE OCCURING AT INLAND TAF SITES WITH LOW
CLOUDS SCATTERING OUT AND/OR CLEARING BY LATE THIS MORNING, THE
EXCEPTION BEING HAF WHERE LOW CEILINGS WILL LIKELY PREVAIL. ONSHORE
WINDS WILL INCREASE ONCE AGAIN THIS AFTERNOON BEFORE EASING AFTER
SUNSET AROUND THE MONTEREY BAY TERMINALS AND OVERNIGHT ACROSS THE
BAY AREA TERMINALS. THERE IS HIGH CONFIDENCE FOR BOTH THE MONTEREY
BAY AND SAN FRANCISCO BAY TERMINALS TO SEE AN EARLY RETURN OF
LIFR/IFR/MVFR CEILINGS THIS EVENING THAT WILL PERSIST THROUGH MID-
MORNING ON WEDNESDAY.
VICINITY OF SFO...VFR AT SFO. MVFR AT OAK. EXPECTING CEILINGS TO
LIFT TO VFR WITHIN THE NEXT FEW HOURS, BUT ONLY BRIEFLY. ONSHORE
WINDS INCREASE ONCE AGAIN THIS AFTERNOON. HIGH CONFIDENCE FOR AN
EARLY RETURN OF IFR/MVFR CEILINGS THIS EVENING THAT WILL PERSIST
THROUGH MID-MORNING ON WEDNESDAY. ONSHORE WINDS INCREASE ONCE
AGAIN WEDNESDAY AFTERNOON AS SKY CONDITIONS RETURN TO VFR
(MODERATE CONFIDENCE).
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...LIFR CONDITIONS PERSIST AT MRY THIS MORNING
WHILE SNS HAS RETURNED TO VFR. THERE IS MODERATE CONFIDENCE THAT MRY
WILL STAY IFR/MVFR THROUGH MUCH OF THE DAY, BUT DO HAVE THEM
SCATTERING OUT AROUND 20Z. ONSHORE WINDS INCREASE THIS AFTERNOON
BEFORE EASING AFTER SUNSET. HIGH CONFIDENCE FOR AN EARLY RETURN OF
LIFR/IFR CONDITIONS THIS EVENING THAT WILL LIKELY PERSIST THROUGH
WEDNESDAY MORNING. THERE IS THE POTENTIAL FOR FOG EARLY WEDNESDAY
MORNING AT MRY AS WELL.
MARINE
(TODAY THROUGH SUNDAY)
ISSUED AT 935 AM PDT TUE AUG 12 2025
A GENTLE TO MODERATE NORTHWESTERLY BREEZE WILL PREVAIL TODAY,
INCREASING TO BECOME FRESH TO STRONG WEDNESDAY WITH WIDESPREAD
STRONG GUSTS BY THURSDAY. MODERATE SEAS WILL BUILD TO BECOME
ROUGH FOR INNER WATERS AND OUTER WATERS BY THURSDAY.
BEACHES
ISSUED AT 248 AM PDT TUE AUG 12 2025
A LONG PERIOD (17 SECONDS) SOUTHWESTERLY SWELL WILL RESULT IN AN
INCREASED RISK FOR SNEAKER WAVES AND RIP CURRENTS THROUGH THIS
EVENING. GREATEST RISK WILL BE ALONG SOUTHWEST FACING BEACHES,
INCLUDING BUT NOT LIMITED TO STINSON BEACH, SANTA CRUZ BOARDWALK
BEACH, AND TWIN LAKES BEACH. SNEAKER WAVES CAN UNEXPECTEDLY RUN
SIGNIFICANTLY FARTHER UP THE BEACH THAN NORMAL, INCLUDING OVER
ROCKS AND JETTIES. REMAIN OUT OF THE WATER TO AVOID HAZARDOUS
SWIMMING CONDITIONS AND NEVER TURN YOUR BACK ON THE OCEAN!
SARMENT
MTR WATCHES/WARNINGS/ADVISORIES
CA...BEACH HAZARDS STATEMENT UNTIL 9 PM PDT THIS EVENING FOR CAZ505-
529.
PZ...SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR SF BAY N OF
BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 1 PM TO 9 PM PDT WEDNESDAY FOR SF BAY
N OF BAY BRIDGE.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY FOR PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 PM WEDNESDAY TO 3 AM PDT THURSDAY
FOR PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...KR
LONG TERM....KR
AVIATION...RGASS
MARINE...SARMENT
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