866
FXUS66 KMTR 302020
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
120 PM PDT MON JUN 30 2025
..NEW SYNOPSIS, SHORT TERM, LONG TERM
SYNOPSIS
ISSUED AT 120 PM PDT MON JUN 30 2025
-TYPICAL MARINE LAYER STRATUS PATTERN THIS WEEK.
-10 PERCENT CHANCE FOR DRY THUNDERSTORMS IN THE NORTH BAY TUESDAY
NIGHT.
-NEAR NORMAL TEMPERATURES WITH A COOLING TREND LATE WEEK.
-BREEZY NORTHWEST WINDS THURSDAY AFTERNOON AND EVENING.
SHORT TERM
(THIS EVENING THROUGH TUESDAY)
ISSUED AT 120 PM PDT MON JUN 30 2025
SKIES ARE SUNNY ACROSS THE DISTRICT WITH A 1200 FOOT MARINE LAYER
ALONG THE IMMEDIATE COAST. CONVECTION NOTED THIS MORNING REMAINS
OFFSHORE, WELL WEST OF THE SONOMA COAST AND CONTINUES TO MOVE AWAY
FROM OUR COASTAL WATERS. WELL TO OUR NORTH UP IN TRINITY COUNTY
SOME OF THE FIRST CONVECTION OVER LAND ASSOCIATED WITH THE UPPER
LOW WEST OF BIG SUR IS STARTING TO INITIATE AND THAT IS BEING
CAPTURED FAIRLY WELL BY THE CAM MODELS. IN TERMS OF SENSIBLE
WEATHER FOR THE BAY AREA ITS A PRETTY SEASONAL AFTERNOON WITH
TEMPS 60S COAST, 70S BAYSIDE, 80S INLAND AND 90S FOR THE INTERIOR
HOT SPOTS OF THE CENTRAL COAST. FOR TONIGHT THE WELL DEFINED
MARINE LAYER ALONG THE COAST WILL SPREAD INTO THE COASTAL VALLEYS
ONCE AGAIN. WITH A DEPTH UNDER 1500 FEET IT SHOULDN'T SPREAD TOO
FAR INLAND. SIMILAR TO THE LAST FEW EVENINGS SOME COASTAL DRIZZLE
AND FOG IS LIKELY DURING THE EVENING AND OVERNIGHT HOURS.
FOR TUESDAY THE UPPER LOW WONT MOVE TOO MUCH BUT INCH CLOSER THE
COAST. INSTABILITY ROTATING AROUND THE LOW WILL REMAIN FOCUSED
OVER THE SIERRA AND MOUNTAINS OF NORTHERN CALIFORNIA, KEEPING
THE BEST THUNDERSTORM CHANCES OVER THE HIGHER TERRAIN (WHERE RED
FLAG WARNINGS ARE CURRENTLY IN EFFECT) AND LIKELY AVOIDING THE
BAY AREA THROUGH AT LEAST TUESDAY AFTERNOON. THUS EXPECT ANOTHER
SUNNY AND SEASONABLE DAY FOR THE FIRST OF JULY ACROSS THE BAY AREA
WITH NO UNSEASONABLY HOT TEMPS FORECAST.
LONG TERM
(TUESDAY NIGHT THROUGH NEXT SUNDAY)
ISSUED AT 120 PM PDT MON JUN 30 2025
ABOUT A 10 PERCENT CHANCE THAT A STRAY THUNDERSTORM OR TWO COULD
SNEAK INTO EXTREME NORTHERN SONOMA OR NAPA COUNTIES TUESDAY
EVENING PER SOME OF THE LATEST HRRR/HREF RUNS WHILE EVEN THE GFS
SHOWS SOME MUCAPE BULLSEYES OVER NORTHERN NAPA COUNTY AROUND 03Z
WEDS. ALL THAT BEING SAID THE MOST LIKELY SCENARIO IS ANY
CONVECTION STAYS NORTH AND EAST OF THE BAY AREA. HOWEVER, ANY
SLIGHT BOBBLE IN THE LOCATION OF THE UPPER LOW COULD SEND A VORT
LOBE OVER MID-LEVEL INSTABILITY FURTHER SOUTH THAN CURRENTLY
EXPECTED.
ON WEDS THE UPPER LOW WILL FINALLY EJECT AND THE MAIN FLOW WILL
TURN MORE WESTERLY, ENDING THE T-STORM THREAT AND ASSOCIATED
INSTABILITY. BY WEDS AFTERNOON WEAK SHORTWAVE RIDGE WILL TRY AND
BUILD OVER THE CENTRAL COAST.
YET ANOTHER LATE SEASON TROUGH IS FORECAST TO APPROACH THE REGION
BY THURSDAY. THIS ONE WILL BE MORE PROGRESSIVE (VERSUS CUT-OFF)
WITH SLIGHTLY COOLER AIR ALOFT. MAIN CONCERN WOULD BE SLIGHTLY
STRONGER WESTERLY WINDS THURSDAY AFTERNOON AND EVENING TO COINCIDE
WITH ANY PRE 4TH OF JULY ACTIVITIES. TEMPERATURES WILL REMAIN NEAR
OR SLIGHTLY BELOW NORMAL AND THE MARINE LAYER COULD DEEPEN TO 3000
FEET OR SO LATER THURSDAY INTO FRIDAY.
TROUGH AXIS PASSES OVERHEAD ON 4TH OF JULY MEANING NO UNSEASONABLY
HOT TEMPS TO CONTEND WITH MAINLY 70S AND 80S INLAND. QUIET AND
UNEVENTFUL WEATHER FORECAST THROUGH THE WEEKEND WITH A GENERAL
TROUGH IN PLACE AT LEAST THROUGH JULY 7TH. BY AROUND JULY 8-10TH
SOME HINTS THAT THE FOUR-CORNERS RIDGE COULD START TO EXPAND AND
BUILD SOME HEAT FARTHER NORTHWARD BUT CONFIDENCE REMAINS LOW TO
MEDIUM GIVEN THE RESILIENCY OF THE WEST COAST TROUGH THE LAST 4-5
WEEKS.
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...RW
LONG TERM....RW
AVIATION...KENNEDY
MARINE...KENNEDY
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