361
FXUS66 KMTR 011731
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1031 AM PDT TUE JUL 1 2025
..NEW AVIATION
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.
UPDATE
ISSUED AT 904 AM PDT TUE JUL 1 2025
NO CHANGES TO THE MORNING FORECAST. WE'RE KEEPING AN EYE ON
SATELLITE IMAGERY, WITH THE STRATUS GRADUALLY ERODING FOR OUR
SERVICE AREA. TO OUR NORTH, THUNDERSTORMS ROLL OVER NORTHERN
MENDOCINO AND NORTHERN LAKE COUNTIES WITH CUMULUS BEING PEPPERED
TO THE NORTH AND EAST OF THE NORTH BAY. THE THUNDERSTORM RISK,
WHICH IS AT A 10 PERCENT CHANCE OR LESS, FOR THE NORTH BAY HOLDS
TODAY. CURRENT THINKING IS THAT THE BEST CHANCES FOR THUNDERSTORMS
SHOULD BE OVER THE NORTHERN PORTIONS OF SONOMA AND NAPA COUNTIES.
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
(18Z TAFS)
ISSUED AT 1030 AM PDT TUE JUL 1 2025
VFR CONDITIONS GRADUALLY RETURNING TO MOST TAF SITES AT THIS HOUR,
WITH THE EXCEPTION BEING HAF WHERE LIFR-MVFR CEILINGS MAY PREVAIL
FOR MOST OF THE TAF PERIOD. THIS IS DUE TO A MARINE LAYER OF AROUND
1500 FEET IN DEPTH. ONSHORE WINDS WILL INCREASE ONCE AGAIN THIS
AFTERNOON BEFORE EASING AFTER SUNSET. HIGH CONFIDENCE FOR LIFR/IFR
CEILINGS TO RETURN LATE THIS EVENING AT THE MONTEREY BAY TERMINALS
WITH LOWER CONFIDENCE FOR IFR/MVFR AT THE BAY AREA TERMINALS EARLY
WEDNESDAY MORNING. ANY LOW CLOUDS WILL LIKELY SCATTER OUT OR
DISSIPATE BETWEEN 16-18Z WEDNESDAY WITH AN INCREASE IN ONSHORE FLOW,
SIMILAR TO THIS MORNING.
VICINITY OF SFO...VFR. INCREASED ONSHORE WINDS THIS AFTERNOON WITH
GUSTS TO AROUND 25 KT AT SFO, WINDS GRADUALLY EASE AFTER SUNSET.
MODERATE CONFIDENCE FOR A RETURN OF IFR/MVFR CEILINGS EARLY
WEDNESDAY MORNING. ANY LOW CLOUDS THAT DO DEVELOP WILL LIKELY
SCATTER OUT OR CLEAR BETWEEN 16-18Z WEDNESDAY WITH AN INCREASE IN
ONSHORE WINDS ONCE AGAIN.
SFO BRIDGE APPROACH...VFR. EXPECTING A LATER RETURN OF STRATUS
ACROSS THE APPROACH WEDNESDAY MORNING WITH SIMILAR CLEARING TIME AS
SFO.
MONTEREY BAY TERMINALS...VFR. INCREASE ONSHORE WINDS THIS AFTERNOON
WITH WINDS EASING AFTER SUNSET. HIGH CONFIDENCE FOR AN EARLY RETURN
OF LIFR/IFR CEILINGS LATE THIS EVENING AND LOWERING (AT TIMES
REDUCED VISIBILITIES) INTO WEDNESDAY MORNING.
MARINE
(TODAY THROUGH SUNDAY)
ISSUED AT 904 AM PDT TUE JUL 1 2025
SIGNIFICANT WAVE HEIGHTS WILL BUILD 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 GALE FORCE BY MIDWEEK. WINDS
AND SEAS REMAIN ELEVATED ACROSS THE COASTAL WATERS THROUGH THIS
WEEK AND INTO NEXT WEEK.
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.
UPDATE...KR
SHORT TERM...MM
LONG TERM....MM
AVIATION...RGASS
MARINE...RGASS
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