847
FXUS66 KMTR 300936
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
236 AM PDT MON JUN 30 2025
..NEW SYNOPSIS, SHORT TERM, LONG TERM
SYNOPSIS
ISSUED AT 1256 AM PDT MON JUN 30 2025
-TYPICAL MARINE LAYER STRATUS PATTERN THIS WEEK.
-SMALL CHANCE FOR DRY THUNDERSTORMS IN THE NORTH BAY TODAY, AND
AGAIN LATE TUESDAY THROUGH WEDNESDAY MORNING.
-NEAR NORMAL TEMPERATURES WITH A COOLING TREND LATE WEEK.
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 1256 AM PDT MON JUN 30 2025
STRATUS HAS PUSHED INLAND A BIT THIS MORNING. THE FT. ORD PROFILER
IS MEASURING THE MARINE LAYER DEPTH AT ROUGHLY 1,200 FEET. NW
WINDS ARE EASING TO A LIGHT BREEZE AS THE BOUNDARY LAYER
DECOUPLES. MIN TEMPS THIS MORNING WILL BE NEAR NORMAL IN THE LOW
TO MID 50S. WHILE THESE SURFACE CONDITIONS ARE ALL FAIRLY TYPICAL
FOR SUMMER, THE PATTERN IS A BIT MORE INTERESTING THAN NORMAL. A
500 MB CUT-OFF LOW JUST OFFSHORE THE SAN FRANCISCO BAY AREA IS
BRINGING S TO SE WINDS TO THE MIDDLE TROPOSPHERE, SURROUNDED BY NW
WINDS AT THE SURFACE AND SW WINDS IN THE JET STREAM. THIS COMPLEX
WIND PROFILE HAS THE POTENTIAL TO BRING ELEVATED MOISTURE FROM THE
SUBTROPICS, WITH MODEL GUIDANCE SUGGESTING THE PWAT WILL EXCEED
1" IN THE NORTH BAY (ROUGHLY 150%-200% OF NORMAL). THERE IS A
GREAT DEAL OF VARIANCE REGARDING THE AMOUNT, TIMING, AND LOCATION
OF THIS MOISTURE PLUME. THERE IS MORE AGREEMENT THAT THE MOISTURE
WILL BE ELEVATED, WITH DRIER AIR BETWEEN THE TOP OF THE MARINE
LAYER AND 850 MB. THIS SET-UP OF UNSTABLE HUMID AIR ABOVE DRY AIR
HAS THE POTENTIAL TO PRODUCE DRY THUNDERSTORMS, WHERE THE RAIN
EVAPORATES BEFORE IT REACHES THE SURFACE. IN THESE STORMS, ANY
CLOUD-TO-GROUND LIGHTNING HAS A MUCH BETTER CHANCE TO IGNITE
WILDFIRES SINCE THERE IS LITTLE TO NO RAIN TO INHIBIT IGNITION.
THE BEST CHANCE FOR THESE STORMS IS OUTSIDE OF OUR AREA IN THE
HIGHER TERRAIN OF THE SIERRA AND CASCADES IN NORTHERN CALIFORNIA.
FORTUNATELY THE CHANCES OF THESE STORMS DEVELOPING REMAINS LESS
THAN 10% IN THE NORTH BAY, WITH THE PROBABILITY DECREASING FURTHER
SOUTH.
LONG TERM
(TUESDAY THROUGH SUNDAY)
ISSUED AT 1256 AM PDT MON JUN 30 2025
THE UPPER LEVEL LOW WILL GRADUALLY SHIFT SOUTH, REACHING SOUTHERN
CALIFORNIA BY WEDNESDAY. ANOTHER PULSE OF MOISTURE WILL PUSH
THROUGH LATE TUESDAY OR EARLY WEDNESDAY MORNING, THIS TIME COMING
FROM THE NORTH AHEAD OF A COLD FRONT. MID-LEVEL LAPSE RATES
INCREASE TO AROUND 8 C/KM, REINVIGORATING THE CHANCES FOR
THUNDERSTORMS. THE NBM IS KEEPING THE CHANCES LESS THAN 10%, BUT
THE NAM BRINGS MUCAPE NEAR 900 J/KG AT SANTA ROSA WEDNESDAY
MORNING. THAT'S JUST ONE DETERMINISTIC MODEL, AND REMAINS AN
OUTLIER, BUT IT WILL BE INTERESTING TO SEE WHAT THE OTHER HIGH
RESOLUTION MODELS COME UP WITH AS THEY START TO RESOLVE
WEDNESDAY'S PATTERN. WITH MUCH DRIER AIR AROUND 900 MB, THERE WILL
BE SOME CONVECTIVE INHIBITION TO OVERCOME AS WELL. BESIDES THE
CONVECTIVE CHANCES, THE SLOW MOVING LOW WILL LIKELY DEEPEN THE
MARINE LAYER A BIT ACROSS THE CENTRAL COAST. THE 850 MB
TEMPERATURE WILL REMAIN WELL ABOVE NORMAL UNTIL A COLD FRONT
MOVES THROUGH LATE WEDNESDAY OR EARLY THURSDAY. THIS WILL BE
FOLLOWED BY A COOLING TREND INLAND, WITH STRONGER ONSHORE WINDS IN
THE AFTERNOON. IN ADDITION TO STRONGER WINDS, A DRIER AIR MASS
WILL ALSO FOLLOW THE COLD FRONT, MARGINALLY INCREASING FIRE
WEATHER CONDITIONS. FORTUNATELY THE ONSHORE WINDS WILL RETAIN
SOME MOISTURE, AND THE TEMPS WILL BE BELOW NORMAL, KEEPING THE
CONDITIONS MORE MODERATE AND LOCALIZED. A SECOND TROUGH WILL MOVE
THROUGH FRIDAY, EXTENDING THE COOLER THAN AVERAGE TEMPERATURES
INTO THE HOLIDAY WEEKEND.
AVIATION
(06Z TAFS)
ISSUED AT 958 PM PDT SUN JUN 29 2025
IFR-LIFR STRATUS FORMING FROM THE IMMEDIATE COAST INTO THE MONTEREY
BAY AND PARTS OF THE BAY AREA, EXPANDING ACROSS THE COASTAL VALLEYS
THROUGH THE NIGHT BEFORE RETREATING BACK TO THE IMMEDIATE COAST
MONDAY MORNING. STILL MORE CONFIDENT THAN NOT THAT SFO AVOIDS A
CEILING, ALTHOUGH MODEL OUTPUT HAS INCREASED THE CHANCES FOR STRATUS
DEVELOPMENT ACROSS THE REST OF THE BAY AREA. HAVE ISSUED A TEMPO FOR
IFR CEILINGS AT SJC AS A RESULT. BREEZY ONSHORE WINDS PERSIST FOR A
COUPLE MORE HOURS BEFORE RESUMING ON MONDAY AFTERNOON WITH MORE OF A
WESTERLY FLOW ACROSS THE COASTAL WATERS, ESPECIALLY IN THE CENTRAL
COAST.
VICINITY OF SFO... VFR CONDITIONS CONTINUE WITH MODERATE TO HIGH
CONFIDENCE THAT THEY PERSIST OVERNIGHT, ALTHOUGH MODEL OUTPUT HAS
INCREASED THE CHANCES FOR STRATUS DEVELOPMENT ACROSS THE REST OF THE
BAY AREA. IF STRATUS DOES FORM AT THE TERMINAL, IT WILL BE BRIEF AND
QUICK TO DISSIPATE IN THE COUPLE OF HOURS AFTER SUNRISE. BREEZY
NORTHWEST FLOW CONTINUES FOR A COUPLE MORE HOURS, WITH LIGHT WINDS
OVERNIGHT BEFORE THE NORTHWEST WINDS RESUME MONDAY AFTERNOON.
SFO BRIDGE APPROACH... SIMILAR TO SFO.
MONTEREY BAY TERMINALS... LIFR STRATUS CURRENTLY OVER SNS AND
EXPANDING OVER MRY WITHIN THE NEXT HOUR, PERSISTING THROUGH MONDAY
MORNING WITH BREEZY ONSHORE WINDS RESUMING MONDAY AFTERNOON.
MARINE
(TONIGHT THROUGH NEXT SATURDAY)
ISSUED AT 958 PM PDT SUN JUN 29 2025
SIGNIFICANT WAVE HEIGHTS AND WINDS CONTINUE TO DIMINISH THROUGH
EARLY TUESDAY MORNING. LOCALLY BREEZY, FRESH TO STRONG, NORTHWEST
GUSTS PERSIST ACROSS THE OUTER COASTAL WATERS WITH EMPHASIS ON THE
FAR NORTHERN OUTER WATERS NORTH OF POINT REYES. SOUTH TO
SOUTHWEST WINDS CONTINUE ACROSS THE INNER COASTAL WATERS NORTH OF
POINT PINOS. SIGNIFICANT WAVE HEIGHTS BUILD AGAIN ON TUESDAY WITH
STRONG NORTHWEST BREEZES AND MODERATE TO ROUGH SEAS THAT WILL
PERSIST INTO THE LATER PART OF THE WEEK.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 9 PM TUESDAY TO 3 AM PDT WEDNESDAY FOR
PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...FLYNN
LONG TERM....FLYNN
AVIATION...DIALH
MARINE...DIALH
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