748
FXUS66 KMTR 251156
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
456 AM PDT TUE AUG 25 2026
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 1202 AM PDT TUE AUG 25 2026
- TEMPERATURES NEAR TO SLIGHTLY BELOW SEASONAL AVERAGES PERSIST
WITHIN THE MARINE LAYER THROUGH THURSDAY
- SEASONABLY WARM AND DRY CONDITIONS CONTINUE ABOVE 1000 FEET
- PATTERN CHANGE FRIDAY INTO THE WEEKEND BRINGS COOLER
TEMPERATURES AND MODERATE POTENTIAL FOR TROPICAL MOISTURE
SHORT TERM
ISSUED AT 1202 AM PDT TUE AUG 25 2026
(TODAY AND TONIGHT)
SATELLITE IMAGERY SHOWS AN EXPANDING STRATUS LAYER BELOW
SCATTERED HIGH CLOUDS, WITH LOW CLOUDS PRESENT IN THE VALLEYS OF
SOUTHERN SONOMA COUNTY, THE SAN FRANCISCO BAY REGION, AND DOWN THE
SALINAS VALLEY. COASTAL DRIZZLE HAS BEEN OBSERVED AT THE OFFICE,
AND HAS BEEN ADDED TO THE GRIDS TONIGHT. THE STRATUS DECK IS
EXPECTED TO CONTINUE DEVELOPING INTO THE SF BAY REGION THROUGH THE
NIGHT BEFORE RETREATING BACK TO THE COASTAL REGIONS AFTER
SUNRISE.
AFTER A SLIGHT DIP IN THE TEMPERATURES YESTERDAY, TEMPERATURES WILL
TICK UPWARD TODAY AS THE BALANCE BETWEEN TROUGHING IN THE EASTERN
PACIFIC AND RIDGING OVER THE DESERT SOUTHWEST SWINGS BACK TOWARDS
THE RIDGING INFLUENCE. TEMPERATURES RANGE FROM THE 80S INTO THE
MIDDLE 90S FOR THE INLAND VALLEYS, UP TO AROUND 104 IN THE SOUTHERN
TIER OF MONTEREY COUNTY, THE UPPER 60S TO THE LOWER 80S NEAR THE
BAYS, AND THE UPPER 50S TO MIDDLE 60S ALONG THE PACIFIC COAST.
BREEZY ONSHORE WINDS WILL DEVELOP THIS AFTERNOON AND EVENING, WITH
WIND GUSTS 20 TO 30 MPH ALONG THE COAST AND THROUGH FAVORED GAPS AND
PASSES. THE MARINE LAYER WILL REMAIN AROUND 1000-1500 FT TODAY, WITH
WARM AND DRY CONDITIONS ABOVE THE MARINE LAYER INVERSION. SEE THE
FIRE WEATHER SECTION FOR THE IMPLICATIONS FOR LOCAL FIRE WEATHER
CONCERNS.
LONG TERM
ISSUED AT 1202 AM PDT TUE AUG 25 2026
(WEDNESDAY THROUGH MONDAY)
THE RIDGING PREVAILS INTO THURSDAY WITH TEMPERATURES IN THE MIDDLE
80S TO THE MIDDLE 90S INLAND AND THE 70S INTO THE MIDDLE 80S NEAR
THE BAYS. A PATTERN CHANGE BEGINS ON FRIDAY WITH UPPER LEVEL
TROUGHING DEVELOPING OVER THE WEST COAST, BRINGING COOLER
TEMPERATURES AND BREEZIER WINDS TO THE REGION. TEMPERATURES IN THE
INLAND VALLEYS DIP INTO THE 80S FOR THE WEEKEND, AND COOL FURTHER
WITH HIGHS DIPPING INTO THE MIDDLE 70S TO LOWER 80S EARLY NEXT WEEK.
EVEN THE WARM SPOTS OF THE INTERIOR CENTRAL COAST COOL INTO THE
MIDDLE TO UPPER 80S BY MONDAY. THE STRENGTHENING PRESSURE GRADIENT
WILL ALLOW STRONGER ONSHORE FLOW TO DEVELOP STARTING ON FRIDAY, WITH
WIND GUSTS OF 25 TO 35 MPH EXPECTED ALONG THE COAST, THROUGH FAVORED
GAPS AND PASSES, AND WITHIN THE NORTHERN SALINAS VALLEY.
WE CONTINUE TO MONITOR AN ACTIVE TROPICAL EASTERN PACIFIC AND ITS
INDIRECT IMPACTS TO THE REGION. TROPICAL STORM ISELLE CONTINUES TO
MARCH NORTHWESTWARD OFF THE COAST OF WESTERN MEXICO, AND A TROPICAL
DEPRESSION HAS SPUN UP FOR AROUND A DAY OR SO BEFORE IT GETS
ABSORBED INTO ISELLE. IN ADDITION, OUR COLLEAGUES AT THE NATIONAL
HURRICANE CENTER ARE TRACKING THREE POTENTIAL DEVELOPMENT AREAS
THROUGH THE NEXT WEEK. NONE OF THESE STORMS ARE EXPECTED TO DIRECTLY
IMPACT THE STATE, BUT LONG-PERIOD SWELL GENERATED BY THE INTENSE
WINDS WITHIN THE STORMS IS EXPECTED TO BEGIN ARRIVING FRIDAY INTO
THE WEEKEND. THE CURRENT FORECAST REMAINS JUST BELOW BEACH HAZARDS
STATEMENT CRITERIA, BUT THIS WILL GET REFINED THROUGH THE NEXT
COUPLE OF DAYS. THERE'S ALSO AN INCREASING CHANCE THAT TROPICAL
MOISTURE WILL IMPACT THE REGION DURING FRIDAY AND THE WEEKEND, WITH
THE MODEL TREND BEING TO PUSH THE MOISTURE PLUME FARTHER UP THE
COAST INTO THE BAY AREA AND CENTRAL COAST. THE NBM CONTINUES TO SHOW
A VERY LOW (BELOW 5% PROBABILITY), BUT NON-ZERO, CHANCE FOR
THUNDERSTORMS DURING THIS PERIOD, AND GIVEN THE UNCERTAINTIES
SURROUNDING EASTERN PACIFIC TROPICAL WEATHER, THIS SETUP BEARS
CONTINUED MONITORING.
AVIATION
(12Z TAFS)
ISSUED AT 431 AM PDT TUE AUG 25 2026
A ROBUST MARINE LAYER WAS MEASURED AT ~1800FT WITH THE KOAK 12Z
BALLOON WITH PRIMARILY IFR/LIFR CONDITIONS WITH THE EXCEPTION OF
KAPC, KSJC AND KLVK. MID/HIGH LEVEL CLOUD COVER LIKELY HELPING TO
KEEP THE LATTER THREE TERMINALS IN MVFR/VFR THROUGH MID-MORNING.
MAJORITY OF TERMINALS ARE EXPECTED TO LIFT TO VFR BY LATE MORNING,
WITH KMRY HAVING A 30% CHANCE OF LINGERING PAST NOON PDT.
VICINITY OF SFO...SHOULD REMAIN IFR THROUGH MID/LATE MORNING
BEFORE LIFTING TO VFR FOR THE REMAINDER OF THE DAY AND EVENING
HOURS. KOAK MAY SEE MVFR/IFR CEILINGS RETURN SOON AFTER SUNSET
WITH KSFO MORE LIKELY AROUND MIDNIGHT.
SFO BRIDGE APPROACH...SIMILAR TO KOAK WITH TIMING OF CEILINGS.
MONTEREY BAY TERMINALS...MARINE LAYER IS NOT AS DEEP THIS FAR
SOUTH, HOWEVER LIFR CEILINGS ARE EXPECTED TO PERSIST THROUGH LATE
MORNING, CLEARING OUT OF KSNS FIRST WITH KMRY POSSIBLY LINGERING
INTO EARLY AFTERNOON WITH VFR UNTIL LATE AFTERNOON EARLY EVENING.
IFR/LIFR CONDITIONS EXPECTED FROM THAT POINT ON FOR THE REMAINDER
OF THE FORECAST PERIOD.
MARINE
(TODAY THROUGH SUNDAY)
ISSUED AT 431 AM PDT TUE AUG 25 2026
FRESH BREEZES TODAY WILL BECOME FRESH TO STRONG ON WEDNESDAY AND
PERSIST THROUGH THE REMAINDER OF THE WEEK INTO THE WEEKEND WITH
MODERATE SEAS. LONG PERIOD SOUTHERLY SWELL WILL BEGIN TO BUILD ON
THURSDAY, BECOMING 15 TO 17 SECONDS FOR FRIDAY AND SATURDAY, THEN
BEGIN TO GRADUALLY EASE ON SUNDAY INTO NEXT WEEK.
FIRE WEATHER
ISSUED AT 1202 AM PDT TUE AUG 25 2026
NEAR-CRITICAL FIRE WEATHER CONDITIONS CONTINUE THROUGH THURSDAY FOR
ELEVATIONS ABOVE 1000 FEET AS WARM AND DRY CONDITIONS CONTINUE
ACROSS THE REGION. HUMIDITY RECOVERIES REMAIN POOR TO VERY POOR IN
THE HIGHER ELEVATIONS, WITH NOCTURNAL DRYING EXPECTED WITHIN THE
SANTA LUCIA RANGE. BREEZY CONDITIONS WILL DEVELOP EACH AFTERNOON AND
EVENING, BUT NOT FOR A LONG ENOUGH PERIOD TO TRIGGER ANY FIRE
WEATHER PRODUCTS. SPECIFICALLY REGARDING THE TIMBER FIRE VICINITY,
OBSERVATIONAL DATA SUGGESTS THAT SOUTHWESTERLY WINDS FROM THE
PACIFIC OCEAN OVER THE RIDGETOPS ARE HELPING TO MOISTEN THE AIR,
WITH NOCTURNAL DRYING BEING OBSERVED AS THE WINDS DIMINISH AND EVEN
TURN FAINTLY OFFSHORE OVERNIGHT. THIS HAS LED TO AN UNUSUAL
SITUATION WHERE DAILY MAXIMUM RELATIVE HUMIDITY VALUES HAVE BEEN
OBSERVED DURING THE DAYTIME. SMOKE TRANSPORT FROM THE TIMBER FIRE
WILL CONTINUE TO PEAK IN THE AFTERNOON AND EVENING WITH THE PLUME
SPREADING TOWARDS THE SALINAS AREA. FRIDAY INTO THE WEEKEND, A
PATTERN CHANGE SHOULD ALLOW FOR SOME RELIEF AS AN UPPER LEVEL TROUGH
COMES INTO THE REGION BRINGING COOLER TEMPERATURES AND A DEEPER
MARINE LAYER.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 AM PDT
THURSDAY FOR PIGEON PT TO PT PINOS 0-10 NM-PT ARENA TO PT
REYES 0-10 NM-PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 9 AM PDT THURSDAY
FOR PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES 10-
60 NM.
SHORT TERM...DIALH
LONG TERM....DIALH
AVIATION...JM
MARINE...JM
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