920
FXUS66 KMTR 121753
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1053 AM PDT FRI SEP 12 2025
..NEW AVIATION
KEY MESSAGES
UPDATED AT 240 AM PDT THU SEP 12 2025
- DRIER AND SLIGHTLY WARMER WEATHER FRIDAY AND SATURDAY, MUCH
WARMER EARLY NEXT WEEK WITH MODERATE HEATRISK
UPDATE
ISSUED AT 824 AM PDT FRI SEP 12 2025
STRATUS HAS MADE IT FAR INTO THE INLAND VALLEYS, WITH PROFILERS AT
BODEGA BAY, FORT ORD, AND POINT SUR SUGGESTING A REDEVELOPING
MARINE LAYER AT 1500-2000 FEET DEEP. MORE SEASONAL CONDITIONS ARE
EXPECTED TODAY WITH TEMPERATURES WARMING TO NEAR THE SEASONAL
AVERAGES IN THE INLAND VALLEYS OF THE BAY AREA. NO CHANGES TO THE
FORECAST AT THIS TIME.
DIALH
SHORT TERM
ISSUED AT 311 AM PDT FRI SEP 12 2025
(TODAY AND TONIGHT)
MARINE LAYER IS TRYING TO MAKE A COMEBACK AS NOTED ON THE
OVERNIGHT SATELLITE FOG PRODUCT AND THE BODEGA BAY PROFILER. THE
DEPTH OF THE MARINE LAYER IS CLOSE TO 1500 FEET PER PROFILER,
WHICH IS CLOSE TO MOISTURE X-SECTIONS ON MODEL GUIDANCE. INLAND
CLOUDS WILL SLOWLY ROLL BACK TO THE COAST MID-LATE MORNING, BUT
NOT EXPECTING A FULL CLEARING AT THE COAST. CLOUDS WILL LINGER
FOR MOST OF THE DAY. THE LONGWAVE PATTERN IN THE WEST IS STILL
GRIPPED BY A POSITIVELY TILTED UPPER TROUGH AND EMBEDDED UPPER
LOW. THIS FEATURE CONTINUES TO WEAKEN AND MOVE EASTERLY INTO WHAT
WILL BE AN OPEN WAVE. WAITING IN THE UPPER LEVEL WINGS IS
SHORTWAVE RIDGING. TODAY WILL BE A TRANSITION DAY IN THE LONGWAVE
PATTERN FROM A TROUGH TO A RIDGE. DESPITE SOME COASTAL CLOUDS, DO
EXPECT AN UPTICK (5-10 DEGREES) IN TEMPERATURES TODAY WITH THE
APPROACHING RIDGE.
ONE OTHER ITEM OF NOTE WE'LL BE MONITOR THIS AFTERNOON WILL BE
WILDFIRE SMOKE. WHILE ONE WOULD THINK IT WOULD BE FROM THE GARNET
FIRE OVER ON THE SIERRA IT'S ACTUALLY FIRES BURNING IN WA. GIVEN
THE UPPER LEVEL PATTERN SOME UPPER LEVEL SMOKE WILL BE POSSIBLE.
MORE LIKE SOME UPPER LEVEL HAZE. NO SURFACE SMOKE IS EXPECTED.
A MORE DEFINED MARINE LAYER WILL RETURN TONIGHT WITH A SLIGHTLY
DEEPER PUSH. SOLID HUMIDITY RECOVERY IS EXPECTED OVERNIGHT, BUT
THE HIGHEST PEAKS ABOVE 3-4K FEET WILL BE MODERATE HUMIDITY
RECOVERY AND IN AN ACTIVE THERMAL BELT.
LONG TERM
ISSUED AT 331 AM PDT FRI SEP 12 2025
(SATURDAY THROUGH THURSDAY)
LOOKING PRETTY DRY FOR THE UPCOMING WEEKEND. PREVIOUS MODEL RUNS
BROUGHT A FEW SHOWERS TO NORTHERN AREAS ON SUNDAY, BUT THE 00Z
RUNS HAVE ALL BUT ERASED IT. IN FACT, THE UPCOMING WEEKEND IS
TRENDING WARMER AND DRIER THAN PREVIOUS FORECAST. THE SHORTWAVE
RIDGE WILL SLIDE THROUGH SATURDAY WITH SHORTWAVE TROUGH TO QUICKLY
FOLLOW ON SUNDAY. THE RIDGE WILL CONTINUE THE SUBTLE WARMING
TREND ON SATURDAY WITH HIGHS RANGING FROM THE 60S/70S COAST AND
70S TO NEAR 90 INLAND. TEMPERATURES MODERATE ON SUNDAY AS A TROUGH
PASSES TO THE NORTH. THE PASSING TROUGH HAS A BETTER SHOT AT
PRODUCING PRECIP NORTH OF THE BAY AREA.
TO JUMP START THE WORK WEEK WILL BE ANOTHER UPPER LEVEL RIDGE. THE
HIGHER 500MB HEIGHTS AND WARMER 850MB WILL REINVIGORATE THE
WARMING AND DRYING TREND. BY TUESDAY AND WEDNESDAY 850MB TEMPS
REACH THE LOW 20C RANGE. IF YOU DO THE OLD RULE OF THUMB FOR A
MIXED ATMOSPHERE AND ADD 10-15C YOU CAN GET SURFACE TEMPERATURES
OF 95-100 DEGREES. THOSE VALUES ARE CURRENTLY IN THE FORECAST FOR
FAR INTERIOR LOCATIONS. LINGERING ONSHORE FLOW AND MARINE
INFLUENCE WILL KEEP THE COAST AND BAYS COOLER AND IN THE 70S AND
80S. REGARDLESS, TEMPERATURES WILL BE SEVERAL DEGREES ABOVE
NORMAL. HEATRISK VALUES AWAY FROM THE COAST DO SURGE INTO THE
MODERATE CATEGORY WITH A FEW PIXELS OF MAJOR.
NEXT THURSDAY AND BEYOND GET PRETTY INTERESTING ON THE LONG RANGE
FORECAST. KIND OF FANTASY LAND AT THIS POINT, BUT THERE ARE SIGNS
WE'LL NEED TO WATCH FOR ANOTHER ROUND OF TROPICAL/MONSOONAL
MOISTURE SURGE. IT'S TOO EARLY FOR DETAILS, BUT LONGER RANGE
GLOBAL ENSEMBLES/CLUSTER SHOW TRANSPORT FLOW THAT WOULD BRING
DECAYING TROPICAL SYSTEM MOISTURE WITH A HINT OF MONSOONAL. GFS
MODEL FOR INSTANCE HANDLED THE EARLY SEPTEMBER LIGHTNING EVENT
BETTER THAN OTHERS. IT'S FANTASY LAND PICTURE FOR THE 19-20TH OF
SEPT SHOWS SHOWERS AND THUNDERSTORMS OVER CENTRAL CALIFORNIA. AT
THIS POINT, IT WORTH KEEPING AND EYE ON. TIMING WOULD BE BAD FROM
A FIRE WEATHER STAND POINT AS WARMER WEATHER DEVELOPS OVER THE
WEEKEND AND PEAKS EARLY NEXT WEEK.
AVIATION
(18Z TAFS)
ISSUED AT 1052 AM PDT FRI SEP 12 2025
A MIX OF IFR/MVFR CONDITIONS THIS MORNING WITH A MODERATE TO HIGH
PROBABILITY OF VFR EXPECTED TO RETURN TO THE BAY AREA TERMINALS BY
THIS AFTERNOON. LOWER CONFIDENCE FOR THE MONTEREY BAY TERMINALS
WHERE MVFR CEILINGS HAVE A MODERATE (30-60%) PROBABILITY OF
LINGERING THROUGH MUCH OF THE DAY, HOWEVER STILL EXPECTED A FEW
HOURS OF VFR CONDITIONS TO RETURN IN THE CURRENT TAFS. ONSHORE WINDS
INCREASE THIS AFTERNOON AND EASE LATE THIS EVENING AND MORE SO INTO
SATURDAY MORNING. MODERATE TO HIGH CONFIDENCE FOR IFR/MVFR LATE THIS
AFTERNOON OR EARLY EVENING ACROSS THE MONTEREY BAY TERMINALS AND
MVFR RETURNING LATE THIS EVENING FOR THE BAY AREA TERMINALS.
CEILINGS POTENTIALLY LOWER TO LIFR AROUND THE MONTEREY BAY TERMINALS
AND IFR FOR THE BAY AREA TERMINALS EARLY SATURDAY MORNING BEFORE
LIFTING BY SATURDAY AFTERNOON. ONSHORE WINDS INCREASE ONCE AGAIN
SATURDAY AFTERNOON.
VICINITY OF SFO...MVFR/VFR CEILINGS CURRENTLY WITH A HIGH CONFIDENCE
OF IMPROVING TO VFR BY LATE MORNING OR EARLY AFTERNOON. ONSHORE
WINDS INCREASE THIS AFTERNOON AND BEGIN TO EASE INTO SATURDAY
MORNING. MODERATE TO HIGH CONFIDENCE FOR AN EARLY RETURN TO MVFR
LATE THIS EVENING, POTENTIALLY (LOWER CONFIDENCE) LOWERING TO IFR
EARLY SATURDAY MORNING. CEILINGS WILL THEN LIFT MID-TO-LATE MORNING
ACROSS THE REGION, HOWEVER MODERATE CONFIDENCE FOR MVFR TO LINGER
THROUGH 21Z SATURDAY OR POTENTIALLY LONGER.
SFO BRIDGE APPROACH...MVFR CEILINGS FORECAST RETURN LATER TONIGHT
(GENERALLY AROUND OR AFTER 06Z) AND CLEAR SOONER SATURDAY
MORNING (BETWEEN 18Z-20Z). OTHERWISE, SIMILAR TO SFO.
MONTEREY BAY TERMINALS...THERE IS MODERATE CONFIDENCE (30-60%) FOR
MVFR CEILINGS TO PERSIST THROUGH MUCH OF THE DAY TODAY (ESPECIALLY
AT MRY), HOWEVER STILL EXPECTED A FEW HOURS OF VFR CONDITIONS TO
RETURN IN THE CURRENT TAFS. ONSHORE WINDS INCREASE THIS AFTERNOON
AND DIMINISH AFTER SUNSET. HIGH CONFIDENCE FOR AN EARLY RETURN LATE
THIS AFTERNOON OF IFR/MVFR CEILINGS WITH A LOW TO MODERATE POTENTIAL
FOR LIFR CEILINGS EARLY SATURDAY MORNING.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 824 AM PDT FRI SEP 12 2025
BREEZY NW WINDS AND FRESH GUSTS ARE EXPECTED TODAY WITH LOCALLY
STRONGER GUSTS POSSIBLE ACROSS THE NORTHERN OUTER WATERS AND ALONG
THE BIG SUR COASTLINE. ROUGH SEAS PERSIST ACROSS THE OUTER WATERS
WHILE MORE MODERATE SEAS PERSIST ACROSS THE INNER WATERS. WINDS
DECREASE SATURDAY AS FRESH TO STRONG GUSTS BECOME MORE LOCALIZED
ACROSS THE SOUTHERN COASTAL WATERS. ANOTHER ROUND OF WIDESPREAD
FRESH TO STRONG NW WINDS BEGINS SUNDAY INTO NEXT WEEK WITH THE
STRONGEST WINDS LOCATED ACROSS THE FAR NORTHERN OUTER WATERS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PDT THIS
EVENING FOR MRY BAY-PIGEON PT TO PT PINOS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 AM PDT SATURDAY FOR PT ARENA TO PT
REYES 0-10 NM-PT ARENA TO PT REYES 10-60 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 AM PDT
SATURDAY FOR PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...RGASS
MARINE...RGASS
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