867
FXUS66 KMTR 010505
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1005 PM PDT MON JUN 30 2025
..NEW AVIATION, MARINE
KEY MESSAGES
UPDATED AT 128 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
(06Z TAFS)
ISSUED AT 1004 PM PDT MON JUN 30 2025
COASTAL STRATUS IS INTRUDING INTO THE NORTH BAY VALLEYS, THE EAST
BAY, AND THE MONTEREY BAY REGION WITH ALL BUT THE INTERIOR TERMINALS
EXPECTED TO SEE IFR-LIFR CEILINGS THROUGH TUESDAY MORNING. ONSHORE
FLOW INCREASES TUESDAY AFTERNOON AND EVENING, WHEN BAY AREA WINDS
WILL INCREASE TO AROUND 15 KNOTS.
VICINITY OF SFO...CONDITIONS REMAIN VFR AT THE TERMINAL. THE MARINE
LAYER STRATUS HAS REACHED OAK, BUT IS THEN EXPECTED TO WRAP AROUND
SAN FRANCISCO BAY BEFORE POTENTIAL IMPACTS TO SFO DEVELOP. PAST
EXPERIENCE WITH SIMILAR SITUATIONS HAS LOWERED CONFIDENCE IN TIMING
OF STRATUS IMPACTS WITH A "SUCKER HOLE" SEEN RATHER OFTEN IN THIS
SETUP. MOST LIKELY TIME FRAME FOR STRATUS IMPACTS IS AROUND 12-17Z.
BREEZY ONSHORE FLOW ON TUESDAY AFTERNOON WILL LIFT WINDS TO 15 KNOTS
OR HIGHER.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...IFR-LIFR CEILINGS THROUGH TUESDAY MORNING.
A LIGHT NORTHWEST BREEZE DEVELOPS DURING THE AFTERNOON AND EVENING,
WITH STRATUS COVERAGE RETURNING TO THE TERMINAL SOMETIME TUESDAY
EVENING.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 1004 PM PDT MON JUN 30 2025
SIGNIFICANT WAVE HEIGHTS WILL BUILD EARLY TUESDAY MORNING AS
NORTHWEST WINDS STRENGTHEN AND GRADUALLY SPREAD ACROSS THE OUTER
WATERS THROUGH THE REST OF THE WEEK. WINDS WILL BE STRONGEST
ACROSS THE NORTHERNMOST OUTER WATERS WITH WINDS STRENGTHENING TO
NEAR GALE FORCE BY MIDWEEK. WINDS AND SEAS REMAIN ELEVATED ACROSS
THE COASTAL WATERS THROUGH THE END OF THIS WEEK AND INTO THE
NEXT.
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...DIALH
MARINE...DIALH
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO
FOLLOW US ON FACEBOOK, X, AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSBAYAREA
X.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page