116
FXUS66 KMTR 240657
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1157 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 NORTH
CENTRAL COAST.
- COOLER CONDITIONS ARRIVE FRIDAY INTO THE WEEKEND.
- NEAR SEASONAL TEMPERATURES EARLY NEXT WEEK.
SHORT TERM
ISSUED AT 1157 PM PDT WED SEP 23 2026
(TONIGHT THROUGH FRIDAY)
THERE IS A LARGE VARIATION IN TEMPERATURES ACROSS OUR FORECAST
AREA, WITH 50S IN A SHALLOW MARINE LAYER ALONG THE COASTLINE AND
60S, 70S AND NEAR 80 INLAND AND AT ELEVATION. THE WARMTH IS DUE
TO ONGOING THERMAL AND HEIGHT RIDGING ALOFT WHILE A NARROW CHANNEL
OF COOLER AIR OVER THE COASTAL WATERS IS UNDERCUTTING THE RIDGE.
THERE IS VERY LITTLE TO NO STRATUS OR FOG OVER THE COASTAL WATERS
SINCE THERE IS ALSO WARMER SURFACE TO NEAR SURFACE AIR TEMPORARILY
MIXING IN ON NORTHWEST WINDS. EVEN THOUGH IT'S DRY ALOFT I.E.
GOOD CONDITIONS FOR OUTWARD RADIATIVE COOLING TO HELP STRATUS AND
FOG DEVELOP, THE AIR/SEA INTERFACE IS NOT THERMODYNAMICALLY
SUPPORTIVE OF STRATUS/FOG AT THE CURRENT TIME. HOWEVER, 1000 MB
NAM FORECASTS A RAPIDLY SOUTHEASTWARD MOVING COOLER AIR MASS
ARRIVING IN OUR COASTAL WATERS BETWEEN MIDNIGHT AND THURSDAY
MORNING, WHICH MAY BRIEFLY FALL INTO SYNCOPATION WITH THE
REMAINING RHYTHM OF RADIATIVE COOLING IN THE EARLY MORNING. THIS
COMBINATION WILL LIKELY HELP PRODUCE A FEW AREAS OF COASTAL
STRATUS AND FOG, WHILE INLAND AREAS STAY CLEAR SINCE THE MARINE
LAYER DEPTH IS FORECAST TO REMAIN NEAR STEADY.
DAYTIME HIGHS ON THURSDAY WILL WARM UP SIMILARLY TO WEDNESDAY'S
DAYTIME HIGHS WITH MID 60S TO 70S NEAR THE IMMEDIATE COASTLINE,
70S/80S BAYSIDE TO THE 90S WELL INLAND.
THE RIDGE WILL WEAKEN FRIDAY WITH ONSHORE WINDS DEEPENING, SENDING
COOLER AIR INLAND. DAYTIME HIGHS FRIDAY WILL RANGE FROM THE 60S/70S
COASTSIDE TO THE 80S WELL INLAND.
LONG TERM
ISSUED AT 1157 PM PDT WED SEP 23 2026
(FRIDAY NIGHT THROUGH NEXT WEDNESDAY)
FOR THE WEEKEND, 500 MB TROUGHING WILL RETURN ONCE AGAIN WHICH
WILL KEEP TEMPERATURES COOLER THAN NORMAL FOR LATE SEPTEMBER. IT
SHOULD BE A BEAUTIFUL WEEKEND TEMPERATURE-WISE. AFTER THE WEEKEND
COOLING TREND, TEMPERATURES WILL WARM UP AGAIN BY THE MIDDLE OF
NEXT WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 934 PM PDT WED SEP 23 2026
A RELATIVELY WEAK BUT COMPRESSED MARINE LAYER CONTINUES TO
MAINTAIN VFR CONDITIONS ACROSS OUR AREA. COASTAL SITES ARE
EXPECTED TO SEE MVFR/IFR CEILINGS DEVELOP AFTER MIDNIGHT WITH
INTERIOR LOCATIONS LIKE KSTS AND KSJC POSSIBLY NOT SEEING
STRATUS/FOG UNTIL CLOSER TO SUNRISE. VFR IS EXPECTED AREA WIDE BY
MID/LATE THURSDAY MORNING.
VICINITY OF SFO...MVFR CEILINGS ARE EXPECTED TO DEVELOP DURING THE
OVERNIGHT HOURS, WITH HIGH CONFIDENCE IN VFR CONDITIONS BY MID-
MORNING THURSDAY. GUSTY ONSHORE FLOW DEVELOPS IN THE AFTERNOON
AND WILL CONTINUE INTO THE LATE EVENING HOURS. A FETCH OF WEAK
OFFSHORE FLOW LATE IN THE FORECAST PERIOD MAY LIMIT STRATUS
DEVELOPMENT INTO EARLY FRIDAY MORNING.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...IFR/LIFR CEILINGS ARE EXPECTED TO DEVELOP
AROUND OR SHORTLY AFTER MIDNIGHT AND PERSIST THROUGH MID-MORNING
THURSDAY WITH VFR CONDITIONS EXPECTED THROUGH THE REMAINDER OF THE
TAF PERIOD INTO LATE THURSDAY EVENING.
MARINE
(TONIGHT THROUGH NEXT TUESDAY)
ISSUED AT 934 PM PDT WED SEP 23 2026
NORTH TO NORTHWEST BREEZES WILL CONTINUE TONIGHT, WITH STRONG
GUSTS DEVELOPING THURSDAY AFTERNOON THAT WILL PERSIST THROUGH
FRIDAY, ESPECIALLY FRIDAY AFTERNOON AND EVENING FROM NEARSHORE
SANTA CRUZ TO BIG SUR WITH SEAS RESPONDING AND BECOMING ROUGH 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 9 AM TO 9 PM PDT FRIDAY FOR MRY BAY.
SMALL CRAFT ADVISORY FROM 3 PM THURSDAY TO 9 AM PDT SATURDAY 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 9 AM PDT SATURDAY 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.
SMALL CRAFT ADVISORY FROM 3 AM FRIDAY TO 3 PM PDT SATURDAY FOR
PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES 10-60
NM.
SHORT TERM...CANEPA
LONG TERM....CANEPA
AVIATION...JM
MARINE...JM
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