972
FXUS66 KMTR 171108
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
408 AM PDT WED SEP 17 2025
..NEW SHORT TERM, LONG TERM, MARINE
KEY MESSAGES
UPDATED AT 406 AM PDT WED SEP 17 2025
- DENSE FOG ADVISORY IN EFFECT UNTIL 10AM ALONG THE PACIFIC COAST
AND THE WATERS OF MONTEREY BAY
- ABOVE NORMAL TEMPERATURES WITH WIDESPREAD MODERATE HEATRISK,
THE LAST OF OUR THREE DAY HEAT WAVE
- SHOWERS WITH ISOLATED TO SCATTERED THUNDERSTORMS AS EARLY AS
LATE TONIGHT THROUGH FRIDAY
SHORT TERM
ISSUED AT 406 AM PDT WED SEP 17 2025
(TODAY AND TONIGHT)
AREAS OF DENSE FOG HAVE DEVELOPED ACROSS THE PACIFIC COAST AND THE
WATERS OF MONTEREY BAY WITH A DENSE FOG ADVISORY IN EFFECT UNTIL
10AM ONCE AGAIN THIS MORNING.
THERMAL BELTS REMAIN ACTIVE WITH A MAJORITY OF SITES ABOVE 1500FT AT
70 DEGREES OR HIGHER AND RH VALUES MOSTLY BETWEEN 25%-40%, WITH OAK
RIDGE THE LOWEST AT 16% AS OF 3AM. AS WE WARM TO ABOVE NORMAL
TEMPERATURES FOR THE LAST DAY OF THIS RELATIVELY SHORT HEAT WAVE,
WE'LL ALSO BE KEEPING AN EYE ON THE TROPICAL PLUME OF MOISTURE
WORKING ITS WAY NORTH FROM SOCAL. VANDENBERG RADAR IS PICKING UP
AN AREA OF ELEVATED SHOWERS OVER THE OPEN WATER MOVING DUE NORTH
PAST THE CHANNEL ISLANDS AND POINT CONCEPTION AT THIS HOUR, WHICH
MAY BE A LITTLE AHEAD OF SCHEDULE WITH A NUMBER OF INDIVIDUAL
HIRES CAMS SEEMING TO PICK UP ON THE GENERAL ACTIVITY SO FAR. THE
BULK OF THE FIRST WAVE OF SHOWER ACTIVITY AND ISOLATED
THUNDERSTORMS IS EXPECTED TO REMAIN OFFSHORE AS IT WORKS NORTH
TOWARD OUR LATITUDE LATER TODAY AND TONIGHT. BY LATE TONIGHT INTO
THE EARLY HOURS OF THURSDAY MORNING WE SEE INCREASING CHANCES OF
SHOWERS AND ISOLATED THUNDERSTORMS MOVING INTO SOUTHERN MONTEREY
COUNTY AND SAN BENITO COUNTY. THERE IS STILL A SLIGHT CHANCE OF
DRY THUNDERSTORM ACTIVITY AND LIGHTNING INITIALLY AS THE ACTIVITY
MOVES INTO OUR AREA LATE TONIGHT, BUT WE QUICKLY SHIFT TOWARD MORE
WETTING RAINFALL WITH ENSEMBLE MEAN PWATS INDICATING AROUND
1.40", ASSOCIATED WITH THE LEADING EDGE OF THE REMNANTS OF MARIO
OVER OUR SOUTHERN ZONES BY SUNRISE THURSDAY MORNING. THAT MEAN
VALUE IS 200% OF NORMAL, GIVING HIGH CONFIDENCE THAT WE'LL SEE
NEAR RECORD PWATS WITH THIS EVENT FOR THIS TIME OF THE YEAR.
LONG TERM
ISSUED AT 406 AM PDT WED SEP 17 2025
(THURSDAY THROUGH TUESDAY)
AS MENTIONED ABOVE, THE LEADING EDGE OF THE REMNANTS OF MARIO MOVE
INTO OUR AREA BY EARLY THURSDAY MORNING. ANY THUNDERSTORM ACTIVITY
EARLY THURSDAY MORNING IS EXPECTED TO REMAIN MOSTLY OFFSHORE, BUT
THINGS GET MORE INTERESTING BY LATE MORNING INTO THURSDAY AFTERNOON
AS THE ENVIRONMENT BECOMES MORE FAVORABLE FOR SCATTERED
THUNDERSTORMS TO DEVELOP ACROSS THE CENTRAL COAST INTO THE SOUTH
BAY. GIVEN THE NEAR RECORD PWATS, MUCAPE VALUES BETWEEN 200-400
J/KG, MODERATE PVA, AND BULK SHEAR UP TO 30KTS BY EARLY THURSDAY
AFTERNOON, A FEW STRONG THUNDERSTORMS CAN'T BE RULED OUT
ESPECIALLY ALONG THE SANTA LUCIA AND THE BIG SUR COASTLINE WHERE
TERRAIN COULD ALSO ENHANCE LIFT AT TIMES NEAR THE SURFACE. THE
PRIMARY CONCERN WOULD BE STRONG WIND GUSTS UP TO 50 MPH, CLOUD-TO-
GROUND LIGHTNING AND BRIEF DOWNPOURS GIVEN THE HIGH PWATS THROUGH
EARLY THURSDAY EVENING. THUNDERSTORM ACTIVITY IS EXPECTED TO
GRADUALLY DECLINE AFTER SUNSET WITH SCATTERED SHOWER ACTIVITY
PERSISTING THROUGH THE OVERNIGHT INTO FRIDAY AS THE CENTER OF THE
REMNANTS OF MARIO SHIFTS INTO NORCAL. WEAK RIDGING BUILDS NORTH
OUT OF THE DESERT SOUTHWEST FOR THE WEEKEND, AS ANOTHER WEAK
DISTURBANCE APPROACHES THE WEST COAST FOR THE BEGINNING OF NEXT
WEEK. RAIN CHANCES INCREASE ONCE AGAIN MONDAY AFTERNOON AND
PERSIST INTO TUESDAY.
AVIATION
(06Z TAFS)
ISSUED AT 955 PM PDT TUE SEP 16 2025
FOG IS BUILDING BACK IN ALONG THE COASTLINE WITH HAF CURRENTLY
REPORTING 1/2SM FOG. FOGGY CONDITIONS ARE EXPECTED TO SPREAD TO MRY
AND SNS OVERNIGHT WITH LOW TO MODERATE CONFIDENCE THAT IFR-LIFR CIGS
WILL AT LEAST TEMPORARILY REACH OAK OVERNIGHT. CONFIDENCE IS
INCREASING THAT SITES ALONG THE COAST AND POTENTIALLY OAK WILL SEE
LIFR CIGS GIVEN THE LOWERING MARINE LAYER ACROSS THE BAY AREA.
THINKING REMAINS THAT SAME THAT STRATUS WILL NOT REACH SFO WITH ANY
STRATUS OVER THE BAY LIMITED TO THE EASTERN PORTIONS. FOG AND
STRATUS WILL CLEAR BY LATE MORNING WITH HIGH CLOUDS FILTERING IN
ACROSS THE REGION. NOT ANTICIPATING SHOWERS OR THUNDERSTORMS TO
IMPACT AIRPORTS ON WEDNESDAY BUT THIS WILL BECOME MORE LIKELY
HEADING INTO THURSDAY.
VICINITY OF SFO...VFR THROUGH THE TAF PERIOD. MODERATE CONFIDENCE
THAT STRATUS WILL NOT IMPACT SFO OVERNIGHT. CONFIDENCE IS INCREASING
THAT STRATUS WILL DEVELOP ACROSS EASTERN PORTIONS OF THE BAY
(IMPACTING OAK) BUT WILL NOT FILL IN FAR ENOUGH WESTWARD TO IMPACT
SFO. IF SFO DOES SEE STRATUS DEVELOP OVERNIGHT IT LIKELY WILL NOT
OCCUR UNTIL AFTER 12/13Z. GUSTY AFTERNOON WINDS WILL PEAK AROUND 25
KNOTS BEFORE DECREASING TOMORROW NIGHT.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...LIFR WITH FOGGY CONDITIONS LIKELY DURING
THE EARLY MORNING HOURS. FOG AND LIFR CONDITIONS WILL PERSIST
THROUGH LATE MORNING WITH LOW TO MODERATE CONFIDENCE THAT CONDITIONS
WILL IMPROVE AROUND 17Z. THERE IS SOME POTENTIAL IN MODEL GUIDANCE
FOR CLEARING TO BE DELAYED UNTIL 19/20Z BUT WENT WITH 17Z BASED ON
PERSISTENCE AND NBM GUIDANCE. BRIEF PERIOD OF VFR DURING THE
AFTERNOON/EVENING BEFORE IFR-LIFR CIGS RETURN TOMORROW NIGHT.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 406 AM PDT WED SEP 17 2025
HAZARDOUS CONDITIONS WILL EXIST OVER THE OUTER WATERS THROUGH
FRIDAY DUE TO STRONG NORTHERLY BREEZES AND ROUGH SEAS THAT ARE
DEVELOPING TODAY. CONDITIONS WILL BE LOCALLY WORSE IN THE NORTHERN
OUTER WATERS WHERE GALE FORCE GUSTS AND VERY ROUGH SEAS ARE
LIKELY. SCATTERED THUNDERSTORMS ARE POSSIBLE TODAY AND TOMORROW,
POSING THE RISKS OF LIGHTNING, LOCALLY HEAVY RAINFALL, AND
ERRATIC AND GUSTY WINDS. ISOLATED RAIN SHOWERS WILL LINGER
THROUGH FRIDAY.
FIRE WEATHER
ISSUED AT 225 PM PDT TUE SEP 16 2025
- NEAR CRITICAL FIRE WEATHER CONDITIONS THROUGH WEDNESDAY
- THREAT FOR DRY LIGHTNING HAS DIMINISHED, BUT DIDN'T COMPLETELY
GO AWAY.
NEAR CRITICAL FIRE WEATHER CONDITIONS CONTINUE INTO WEDNESDAY DUE
TO HOT, DRY, AND AFTERNOON BREEZY ONSHORE WINDS. TUESDAY AFTERNOON
FEATURED INTERIOR TEMPS OF A HOT 101 AND A CRISPY 11% AT ARROYO
SECO. EXPECT ANOTHER REPEAT AWAY FROM THE COAST ON WEDNESDAY.
DON'T EXPECT MUCH RELIEF TONIGHT EITHER AS THERMAL BELTS WILL BE
VERY PRONOUNCED WITH MILD AND DRY CONDITIONS OVER THE HIGHER
ELEVATIONS. OVERNIGHT HUMIDITY RECOVERY WILL BE MODERATE TO POOR
OVER THE HIGHEST PEAKS. STILL HAVE CONCERNS REGARDING LOW
CONFIDENCE HIGH IMPACT SCENARIO AS TROPICAL MOISTURE BRINGS A
CHANCE FOR ELEVATED/HIGH- BASED THUNDERSTORMS. AFTER ASSESSING THE
LATEST GUIDANCE AND COORDINATING WITH OTHER OFFICES AND FIRE
PARTNERS DECIDED TO NOT ISSUE ANY FIRE WEATHER WATCH AT THIS TIME.
THE INITIAL THREAT FOR DRY LIGHTNING IS DECREASING WITH FOCUS
OVER THE OCEAN ON WEDNESDAY AND WEDNESDAY NIGHT. IF THE THREAT
SHIFTS EAST WE'LL HAVE TO RE-EVALUATE. ONCE CONVECTION CHANCES
INCREASE OVER LAND THURSDAY ENOUGH MOISTURE SHOULD BE PRESENT
THAT STORMS WILL BE WETTER VS DRIER.
MM
MTR WATCHES/WARNINGS/ADVISORIES
CA...DENSE FOG ADVISORY UNTIL 10 AM PDT THIS MORNING FOR CAZ006-505-
509-529-530.
PZ...DENSE FOG ADVISORY UNTIL 10 AM PDT THIS MORNING FOR MRY BAY.
SMALL CRAFT ADVISORY FROM 9 AM THIS MORNING TO 3 PM PDT THIS
AFTERNOON FOR PT ARENA TO PT REYES 10-60 NM.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 9 AM PDT THURSDAY FOR
PT ARENA TO PT REYES 10-60 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM PDT
THURSDAY FOR PIGEON PT TO PT PINOS 10-60 NM.
SHORT TERM...JM
LONG TERM....JM
AVIATION...SARMENT
MARINE...SARMENT
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