778
FXUS66 KMTR 232158
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
258 PM PDT WED SEP 23 2026
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 1103 AM PDT WED SEP 23 2026
- WARMING TREND CONTINUES INTO THURSDAY BRINGING POCKETS OF
MODERATE HEATRISK ACROSS PARTS OF THE BAY AREA AND CENTRAL
COAST.
- COOLER CONDITIONS ARRIVE FRIDAY INTO THE WEEKEND.
- NEAR SEASONAL TEMPERATURES EARLY NEXT WEEK.
SHORT TERM
ISSUED AT 223 PM PDT WED SEP 23 2026
(THIS EVENING THROUGH THURSDAY NIGHT)
OUR MARINE LAYER WILL CONTINUE TO DEGRADE OFF THE COAST WITH LOW
EXPECTATIONS FOR IT TO REBUILD SIGNIFICANTLY OVERNIGHT. PERSISTENT
ONSHORE WINDS REMAIN LIGHT INTO THURSDAY WITH A WEAK PUSH OF
OFFSHORE FLOW OVERNIGHT ACROSS THE HIGHER ELEVATIONS. DUE TO THE
LACK OF LOW CLOUDS, TEMPERATURES CLIMB INTO THE MID 80S TO LOWER 90S
ACROSS THE INTERIOR NORTH/EAST/SOUTH BAYS WITH THE CENTRAL COAST
EXPERIENCING INLAND TEMPERATURES UP TO THE MID 90S. AS A RESULT,
POCKETS OF MODERATE HEATRISK PERSIST TODAY INTO TOMORROW AFTERNOON,
SPECIFICALLY ALONG THE SAN PABLO BAY SHORELINE, INTERIOR EAST/SOUTH
BAY AND CENTRAL COAST VALLEYS, AS WELL AS THE BIG SUR COASTLINE.
REMEMBER TO STAY HYDRATED BY DRINKING PLENTY OF WATER, WEARING
SUNSCREEN AND LIGHT CLOTHING. THE PACIFIC COASTLINE ALONG THE BAY
AREA AND MONTEREY BAY REGIONS REMAIN COOLER IN THE 60S TO LOWER 70S.
SIMILAR CONDITIONS ARE EXPECTED TO CONTINUE THURSDAY MORNING AS THE
MARINE LAYER IS EXPECTED TO REMAIN CONFINED TO THE COAST WITH POOR
HUMIDITY RECOVERIES OVERNIGHT. THURSDAY AFTERNOON, HOWEVER, MARKS
THE BEGINNING OF A TRANSITION PERIOD TOWARDS COOLER CONDITIONS DUE
TO AN INCREASED PUSH OF STRONG ONSHORE WINDS AHEAD OF AN INCOMING
DRY COLD FRONTAL PASSAGE.
LONG TERM
ISSUED AT 223 PM PDT WED SEP 23 2026
(FRIDAY THROUGH NEXT TUESDAY)
AFTER A COUPLE OF DAYS OF ABOVE NORMAL TEMPERATURES, THINGS WILL
BEGIN TO TRANSITION AS WE ROUND OUT THE END OF THE WORK WEEK AND
VENTURE INTO THE WEEKEND. ON THE SYNOPTIC SCALE THE REGION WILL BE
IN THE WAKE OF AN UPPER TROUGH THAT IS FORECAST TO SWING EASTWARD
THROUGH THE PACIFIC NW. LARGELY NW BREEZES ARE ANTICIPATED AS THE
DIFFUSE FRONTAL BOUNDARY SLIDES SOUTHWARD, HOWEVER, PORTIONS OF
THE CENTRAL COAST (LARGELY THE SANTA LUCIA RANGE) MAY EXPERIENCE
BRIEF PERIODS OF N TO EVEN NNE'LY BREEZES AS SURFACE PRESSURE
RISES ACROSS THE NORTHERN SAC VALLEY LATE FRIDAY INTO SATURDAY.
FORTUNATELY, THE PROBABILITY FOR WIDESPREAD WIND GUSTS EXCEEDING
30 TO 35 MPH REMAINS UNDER 10%, EXCEPT ACROSS PACIFIC COAST
WATERS.
THE UPPER AIR PATTERN WILL REMAIN SOMEWHAT AMPLIFIED THIS WEEKEND
AND INTO EARLY NEXT WEEK. BROAD/DIFFUSE TROUGHING ALONG THE
PACIFIC COAST SHOULD TRANSLATE TO SOME DEGREE OF ONSHORE FLOW.
IT DOESN'T APPEAR THAT THE MARINE LAYER WILL DEEPEN THROUGH 3,000
FEET (OR AT LEAST DEEPEN IT QUICKLY) WITH THE TAIL END OF SOME OF
THE HI-RES GUIDANCE SUGGESTING AROUND 1500-2000 FT. FOR
ELEVATIONS TOWARD THE HIGHER END OF THIS RANGE, CROSS-SECTIONS DO
INDICATE RH POTENTIALLY AS LOW AS THE MID-TEENS WHICH MAY SET THE
STAGE FOR EXTENDED PERIODS OF DRYNESS, PARTICULARLY DURING THE
OVERNIGHT HOURS. SHOULD THIS SIGNAL IN THE NWP PERSIST, FIRE
WEATHER HEADLINES FOR POOR OVERNIGHT HUMIDITY MAY BE WARRANTED
THIS WEEKEND AND INTO EARLY NEXT WEEK. ADDITIONALLY, WE'LL NEED
TO MONITOR THE PROGRESSION OF THE MARINE LAYER AS IT'LL HAVE
RAMIFICATIONS ON THE TEMPERATURE FORECAST AS WE PROGRESS THROUGH
THE WEEKEND. SHOULD THE MARINE LAYER NOT DEEPEN AS MUCH, IT'LL BE
HIGHLY PROBABLE THAT UPWARD ADJUSTMENTS TO MAXT (AND DOWNWARD
ADJUSTMENTS TO RH) WILL BE NEEDED. FOR NOW, THE OFFICIAL FORECAST
WILL ROLL WITH THE DETERMINISTIC NBM WHICH KEEPS TEMPERATURES IN
THE 60S ALONG THE COAST TO THE LOW TO MID 80S ACROSS THE INTERIOR.
OUTSIDE OF OCCASIONAL COASTAL DRIZZLE/MIST/FOG, THERE DOESN'T
APPEAR TO BE ANY REAL OPPORTUNITY FOR WIDESPREAD RAINFALL IN THE
NEXT WEEK OR SO.
AVIATION
(18Z TAFS)
ISSUED AT 1055 AM PDT WED SEP 23 2026
MOSTLY VFR CURRENTLY, THE EXCEPTION IS KHAF WHERE LIFR CONDITIONS
PERSIST. VFR IS EXPECTED BY LATE MORNING AND WILL PERSIST UNTIL
LATE THIS EVENING WHEN SUB-MVFR CONDITIONS RETURN TO THE COASTAL
AREAS. THERE CONFIDENCE IS MODERATE FOR COASTAL LOCATIONS TO
RECEIVE SUB- IFR AND LOWER CONFIDENCE FOR THE BAY AREA TERMINALS
EARLY THURSDAY MORNING. ANY LOW CLOUDS OR FOG THAT DOES DEVELOP
WILL CLEAR BETWEEN 1630Z-1730Z THURSDAY.
VICINITY OF SFO...VFR. ONSHORE WINDS ARE FORECAST TO INCREASE
THIS AFTERNOON, YET NO SIGNIFICANT GUSTS EXPECTED. WIND SPEEDS
EASE OVERNIGHT AND INTO EARLY THURSDAY MORNING WITH A LOW
CONFIDENCE FOR SUB-MVFR (10-30% PROBABILITY) YET MVFR IS MORE
LIKELY WITH 20-50% PROBABILITY AT OR AROUND 11Z THURSDAY. ANY LOW
CLOUDS THAT DOES DEVELOP WILL CLEAR BETWEEN 1630Z-1730Z THURSDAY
WITH INCREASING ONSHORE WINDS BY THURSDAY AFTERNOON.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR. ONSHORE WINDS ARE FORECAST TO
INCREASE THIS AFTERNOON BEFORE EASING AFTER SUNSET. THERE IS
MODERATE CONFIDENCE TO SEE SIMILAR CONDITIONS LATE THIS EVENING
AND INTO THE OVERNIGHT AS WE SAW THIS MORNING. THERE IS MODERATE
CONFIDENCE FOR SUB-IFR (30-50% PROBABILITY) LATE TONIGHT INTO
THURSDAY MORNING BEFORE RETURNING TO VFR BY AROUND 17Z THURSDAY.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 1055 AM PDT WED SEP 23 2026
NORTHERLY BREEZES WILL REMAIN MODERATE TO FRESH OVER THE OUTER
WATERS. LOCALLY HAZARDOUS CONDITIONS WILL PERSIST FOR SMALL CRAFT
OVER THE OUTER WATERS THROUGH WEDNESDAY NIGHT. WINDS WILL WEAKEN
FURTHER ACROSS ALL WATERS ON THURSDAY. FRIDAY WILL SEE AN INCREASE
IN NORTHWEST WINDS ACCOMPANIED BY SEAS BUILDING BACK UP TO ROUGH,
AND CONTINUING INTO THE WEEKEND.
FIRE WEATHER
ISSUED AT 440 AM PDT WED SEP 23 2026
MARINE LAYER RETURNED AGAIN IMPACTING LOWER PORTIONS OF THE
DISTRICT THIS MORNING WITH EXCELLENT RH RECOVERY. SIMILAR TO
YESTERDAY MORNING PATCHY FOG WILL IMPACT THE N BAY VALLEYS,
MONTEREY PENINSULA AND THE SALINAS VALLEY. UNLIKE YESTERDAY TWO
OTHER NOTABLE DIFFERENCES: THE EXACT FOOTPRINT OF THE MARINE
LAYER IS SLIGHTLY DIFFERENT WITH LESS COVERAGE OVER THE E BAY
VALLEYS AND ALONG THE BIG SUR COASTLINE AND MODERATE TO POOR
RECOVERIES ABOVE THE MARINE LAYER. SPEAKING OF THE DRIER
CONDITIONS ALOFT, RH RECOVERIES ARE 15 TO 50 PCT DRIER DEPENDING
ON LOCATIONS. IN OTHER WORDS, NOCTURNAL DRYING RETURNED.
OTHERWISE, WARMER AND DRIER ACROSS THE BOARD, ESPECIALLY INTERIOR
LOCATIONS.
MM
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 5 AM PDT EARLY THIS MORNING FOR
PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY FOR PT ARENA TO PT
REYES 10-60 NM.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PDT THURSDAY FOR PIGEON
PT TO PT PINOS 0-10 NM-PT ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 PM THURSDAY TO 3 AM PDT FRIDAY FOR
PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT THURSDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...NAVARRETE
LONG TERM....BAIN
AVIATION...RGASS
MARINE...RGASS
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