013
FXUS66 KMTR 011023
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
323 AM PDT TUE JUL 1 2025
..NEW KEY MESSAGES, SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 212 AM PDT TUE JUL 1 2025
- ISOLATED SHOWERS EARLY TUESDAY MORNING OVER THE NORTH BAY.
- 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
ISSUED AT 212 AM PDT TUE JUL 1 2025
(TODAY AND TONIGHT)
A LITTLE BIT OF WEATHER EXCITEMENT FOR THE NIGHT SHIFT. RADAR
REMAINS IN PRECIP MODE AS IT CONTINUES TO DETECT A FEW SHOWERS
AND THUNDERSTORMS OVER YOLO COUNTY. GIVEN THE CURRENT STORM MOTION
A FEW OF THESE SHOWERS/THUNDERSTORMS WILL ENTER NE NAPA COUNTY.
IF THEY HOLD TOGETHER THEY COULD (10-20%) REACH NORTHERN SONOMA
COUNTY EARLY THIS MORNING. THE NEAR TERM FORECAST THROUGH ROUGHLY
10 AM HAS BEEN UPDATED TO REFLECT THE LOW CHANCE FOR PRECIP. SO
WHY ARE WE SEEING SHOWERS/THUNDERSTORMS? AN UPPER LEVEL LOW
PRESSURE CONTINUES TO SPIN OFF THE IMMEDIATE COAST. AS SUCH, UPPER
LEVEL MOISTURE IS BEING PULLED IN FROM THE SE AND WRAPPING AROUND
THE UPPER LOW. IN FACT, THESE POCKETS OF UPPER LEVEL MOISTURE ARE
ROUGHLY 110-150% PERCENT OF NORMAL FOR EARLY JULY. COMBINE THE
UPPER LEVEL MOISTURE WITH SOME MID-LEVEL INSTABILITY AND YOU GET
THUNDERSTORMS. MUCAPE, STEEP LAPSE RATES, MODIFIED TOTAL TOTALS,
ARE ALL BEING PICKED UP BY THE MODELS.
OUTSIDE OF PRECIP CHANCES WE'VE FLIPPED THE CALENDAR TO NO SKY
JULY AND THE SATELLITE FOG PRODUCT SHOWS IT WELL. FT ORD PROFILER
SHOWS THE MARINE LAYER DEPTH NEAR 1200-1500 FEET WITH CLOUDS
MOVING INTO THE INLAND VALLEYS. IT'S ALWAYS INTERESTING
METEOROLOGICALLY TO WATCH THUNDERSTORMS/CONVECTION DEVELOP EVEN
WITH A STABLE SURFACE LAYER LIKE STRATUS.
SIMILAR TO THE LAST FEW DAYS, MORNING STRATUS AND FOG WILL SLOWLY
ROLL BACK TO THE COAST BY MID-MORNING. DON'T EXPECT A FULL
CLEARING TODAY AS CLOUDS WILL HUG THE COAST. TEMPERATURES WILL
PEAK IN THE UPPER 50S TO NEAR 70 AT THE COAST AND UPPER 70S TO MID
90S INLAND OR CLOSE TO SEASONAL AVERAGES FOR JULY 1.
ONE THING WILL KEEP AN EYE ON THROUGH OUT THE DAY WILL BE ANOTHER
POTENTIAL FOR SHOWERS/THUNDERSTORM IMPACTING THE NORTH BAY LATE
THIS AFTERNOON AND EARLY TONIGHT. SIMILAR TO WHAT'S HAPPENING NOW
COULD HAPPEN AGAIN. UPPER LEVEL INSTABILITY WITH SOME MOISTURE
MAY LEAD TO A FEW SHOWERS/THUNDERSTORMS ACROSS INTERIOR NORTH BAY
(10-15%)
LONG TERM
ISSUED AT 323 AM PDT TUE JUL 1 2025
(WEDNESDAY THROUGH MONDAY)
THE SLOW MOVING UPPER LEVEL LOW WILL GRADUALLY MOVE INLAND ALONG
THE CENTRAL COAST ON WEDNESDAY BEFORE ULTIMATELY BECOMING AN OPEN
WAVE. IN SHORT, THIS WILL PUT AN END TO ANY PRECIP CHANCES AROUND
THE BAY AREA AND CENTRAL COAST. ALL IN ALL, WEDNESDAY WILL END UP
BEING RATHER PLEASANT.
A MORE PROGRESSIVE UPPER LEVEL PATTERN DEVELOPS ON THURSDAY AS AN
UNSEASONABLY DEEP UPPER LEVEL TROUGH TAKES AIM AT THE PACNW AND
NORCAL. WHILE THE TROUGH LOOKS DRY FOR US IT WILL KEEP TEMPS
COOLER, MARINE LAYER DEEP, AND WINDS BREEZY THROUGH THE DAY.
AS FOR THE UPCOMING 4TH OF JULY, THE UPPER LEVEL TROUGH FINALLY
PASSES OVERHEAD RE-ENFORCING COOLER TEMPERATURES AND PERSISTENT
MARINE LAYER. IF YOU'RE LOOKING FOR CLEAR SKIES THAT EVENING FOR
ANY FIREWORK RELATED ACTIVITIES YOU MAY HAVE A HARD TIME.
RELATIVELY QUIET WEATHER FOR THE UPCOMING WEEKEND. HEADING INTO
NEXT WEEK WE'LL NEED TO MONITOR THE POSSIBLE DEVELOPMENT OF
ANOTHER UPPER LEVEL LOW OFF THE COAST. AS OF NOW, ECM ENS SHOWS
MORE OF A CUT-OFF LOW WHILE OTHER ENS GUIDANCE LESS SO.
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 THIS AFTERNOON TO 9 PM PDT THIS
EVENING FOR SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PDT WEDNESDAY FOR PT
REYES TO PIGEON PT 0-10 NM-SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 9 AM TO 9 PM PDT WEDNESDAY FOR PT
ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM PDT
WEDNESDAY FOR PT ARENA TO PT REYES 10-60 NM.
GALE WARNING FROM 3 PM TO 9 PM PDT WEDNESDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SMALL CRAFT ADVISORY FROM 3 AM TO 9 PM PDT WEDNESDAY FOR PIGEON
PT TO PT PINOS 10-60 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...DIALH
MARINE...DIALH
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