986  
FXUS66 KMTR 301753  
AFDMTR  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAN FRANCISCO CA  
1053 AM PDT MON JUN 30 2025  
   
..NEW AVIATION, MARINE
 
 
   
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.  
 

 
   
UPDATE
 
 
ISSUED AT 928 AM PDT MON JUN 30 2025  
 
KMUX RADAR PUT INTO PRECIP MODE TO COVER ONGOING HIGH BASED  
CONVECTION OCCURRING OVER THE OCEAN WATERS WELL WEST OF SONOMA.  
STORMS MOVING IN A EAST TO WEST DIRECTION AWAY FROM LAND AND  
CURRENTLY MOSTLY BEYOND OUR 60NM MARINE ZONE 570/571. THIS  
CONVECTION WAS NICELY CAPTURED OVER THE LAST 36 HOURS BY MODELS  
USING THE MUCAPE AS A TRACER. LOTS OF CONVECTION EXPECTED ACROSS  
THE NORTHERN PART OF THE STATE THE NEXT 24-36 HOURS BUT FAIRLY  
HIGH CONFIDENCE THAT THE BAY AREA WILL AVOID THUNDERSTORMS THROUGH  
AT LEAST TUESDAY AFTERNOON. BEYOND THAT THE 12Z HRRR AND SOME OF  
THE HREF MEMBERS STILL SHOW A SMALL PERIOD OF CONCERN TUESDAY  
NIGHT INTO THE OVERNIGHT HOURS MAINLY OVER NORTHERN SONOMA AND  
NAPA COUNTIES. CHANCES STILL LOOK TO BE LESS THAN 10 PERCENT BUT  
CANT COMPLETELY RULE OUT SOME THUNDERSTORMS WITH DRY LIGHTNING  
BEING THE BIGGEST CONCERN ESPECIALLY OVER THAT AREA WHERE ERC FUEL  
VALUES ARE TRENDING TOWARDS THE 97TH PERCENTILE.  
 
OTHERWISE STILL LOOKING AT A 1000 FOOT MARINE LAYER THAT HAS  
ALREADY ALMOST PUSHED BACK TO THE COAST. ANOTHER SEASONABLY WARM  
DAY INLAND WITH MILD WEATHER NEAR THE COAST AND BAYS. FORECAST  
FOCUS THROUGH WEDS WILL BE ON LOW PROBABILITY BUT HIGH IMPACT  
SHOULD ANY CONVECTION OCCUR. BY WEDS THE UPPER LOW MOVES INLAND  
AND SOUTHWEST RETURN FLOW REMOVES CONVECTION THREAT.  
 
QUICK GLANCE AT LONG RANGE SUGGESTS A FAIRLY STRONG LATE SEASON  
DRY COLD FRONTAL PASSAGE/UPPER TROUGH BY THURSDAY AFTERNOON INTO  
4TH OF JULY FRIDAY. THIS WILL KEEP TEMPS BELOW NORMAL WITH BREEZY  
ONSHORE WINDS AND DEEP MARINE LAYER. TROUGH TO STAY IN PLACE  
THROUGH THE WEEKEND WITH SOME HINTS OF WARMER RIDGE BEYOND JULY  
8-9TH.  
 

 
   
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
 
 
(18Z TAFS)  
ISSUED AT 1053 AM PDT MON JUN 30 2025  
 
CLOUD COVER HAS DISSIPATED ACROSS ALL AIRPORTS EXCLUDING HAF. VFR  
CONDITIONS WILL PERSIST THROUGH THIS AFTERNOON AND PORTIONS OF THE  
EVENING BEFORE STRATUS RETURNS TONIGHT. EARLIEST RETURNS, OUTSIDE OF  
HAF WHICH IS NOT EXPECTED TO CLEAR, ARE EXPECTED AT MRY AND SNS  
BETWEEN 00Z-04Z THIS EVENING. MODERATE CONFIDENCE IN STRATUS AND IFR  
CONDITIONS REACHING STS, APC, OAK, AND SFO OVERNIGHT. GUIDANCE DOES  
SUGGEST SOME POTENTIAL FOR LIFR CIGS TO DEVELOP BUT CONFIDENCE IS  
LOW. WINDS GENERALLY STAY ONSHORE WITH MOST AIRPORTS OUTSIDE OF STS,  
APC, AND HAF WILL SEE WINDS OUT OF THE NORTHWEST. LOCALLY BREEZY TO  
GUSTY CONDITIONS ARE EXPECTED ACROSS THE SF BAY REGION WITH GUSTS TO  
AROUND 20 KNOTS POSSIBLE AT OAK AND SFO DURING THE AFTERNOON.  
 
VICINITY OF SFO...VFR WITH LOW TO MODERATE CONFIDENCE IN IFR  
CONDITIONS BRIEFLY DEVELOPING OVERNIGHT. CURRENT THINKING IS THAT  
STRATUS WILL BRIEFLY BUILD IN AROUND 12Z BEFORE CLEARING AROUND 17Z.  
LAMP GUIDANCE IS SUPPORTIVE OF STRATUS DEVELOPING CLOSER TO 06Z-09Z  
BUT LEANING MORE TOWARDS HIGH RESOLUTION HRRR GUIDANCE WHICH SHOWED  
CLOUD COVER TAKING SLIGHTLY LONGER TO FILL IN OVER SFO. MODERATE  
WEST TO NORTHWEST WINDS ARE EXPECTED THIS AFTERNOON AND EVENING WITH  
GUSTS TO AROUND 20 KNOTS. WINDS WILL EASE OVERNIGHT AND BECOME  
VARIABLE AT TIMES.  
 
SFO BRIDGE APPROACH...SIMILAR TO SFO.  
 
MONTEREY BAY TERMINALS...STRATUS IS IN THE PROCESS OF CLEARING FROM  
BOTH MRY AND SNS WITH CLEAR SKIES EXPECTED FOR THE REMAINDER OF THE  
AFTERNOON. STRATUS RETURNS BY EARLY THIS EVENING WITH HIGHEST  
CONFIDENCE IN STRATUS ARRIVING BETWEEN 01-04Z. LIFR CIGS AND LOWERED  
VISIBILITIES ARE EXPECTED WITH SOME POTENTIAL FOR FOG TO DEVELOP AT  
MRY AFTER 12Z. CURRENT THINKING IS THAT WHILE VISIBILITIES WILL  
DECREASE SLIGHTLY AT SNS, THEY WILL NOT DECREASE AS MUCH AS AT MRY.  
WINDS STAY ONSHORE THROUGH THE TAF PERIOD WITH LIGHT TO VARIABLE  
WINDS OVERNIGHT.  
 

 
   
MARINE
 
 
(TODAY THROUGH SATURDAY)  
ISSUED AT 1053 AM PDT MON JUN 30 2025  
 
WINDS AND SEAS CONTINUE TO EASE THROUGH TODAY. SIGNIFICANT WAVE  
HEIGHTS WILL BUILD STARTING EARLY TUESDAY MORNING AS NORTHWEST  
WINDS STRENGTHEN AND SPREAD ACROSS THE OUTER WATERS THROUGH THE  
REMAINDER OF THE WORK WEEK. WINDS AND SEAS WILL REMAIN ELEVATED  
ACROSS THE COASTAL WATERS THROUGH THE END OF THIS WEEK AND INTO  
THE NEXT WORK WEEK. LOCALLY BREEZY TO GUSTY CONDITIONS ARE  
POSSIBLE IN THE AFTERNOON AND EVENING ACROSS THE SAN PABLO BAY AND  
SUISUN BAY TODAY.  
 

 
   
MTR WATCHES/WARNINGS/ADVISORIES
 
 
CA...NONE.  
PZ...SMALL CRAFT ADVISORY FROM 3 PM TUESDAY TO 3 AM PDT WEDNESDAY FOR  
PT ARENA TO PT REYES 10-60 NM.  
 

 
 

 
 
SHORT TERM...FLYNN  
LONG TERM....FLYNN  
AVIATION...KENNEDY  
MARINE...KENNEDY  
 
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