225
FXUS66 KMTR 202134
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
234 PM PDT SUN JUL 20 2025
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 231 PM PDT SUN JUL 20 2025
- BELOW NORMAL TEMPERATURES RETURN MONDAY AND CONTINUE THROUGH
THE END OF NEXT WEEK.
- LOCALIZED ELEVATED FIRE WEATHER THREAT FOR THE EAST BAY HILLS
SUNDAY AND MONDAY DUE TO DRY CONDITIONS AND GUSTY WINDS.
- GUSTY WINDS RETURN LATE TONIGHT AND CONTINUE THROUGH MONDAY
NIGHT ALONG THE COAST, RIDGETOPS, AND MOUNTAIN GAPS/PASSES.
SHORT TERM
ISSUED AT 231 PM PDT SUN JUL 20 2025
(THIS EVENING THROUGH MONDAY)
HIGH PRESSURE ACROSS THE REGION HAS MOSTLY BROKEN DOWN WITH UPPER
LEVEL TROUGHING TO BECOME REESTABLISHED THIS EVENING/OVERNIGHT. AS
TROUGHING BECOMES REESTABLISHED, THE MARINE LAYER WILL START TO
DEEPEN FROM APPROXIMATELY 1500 FT (OBSERVED ON THE 12Z OAK SOUNDING)
TO AROUND 2000 FT BY MIDDAY TOMORROW. THIS WILL ALLOW THE MARINE
LAYER TO PUSH FARTHER INLAND OVERNIGHT WITH STRATUS LIKELY TO MAKE
IT INTO THE BAY AREA VALLEYS. AT THE SAME TIME, HIGH TEMPERATURES
TOMORROW WILL COOL TO WELL BELOW NORMAL WITH TEMPERATURES RUNNING
ANYWHERE FROM 5 DEGREES TO 15 DEGREES COOLER THAN AVERAGE. A FEW OF
THE SITES IN THE HIGHER TERRAIN WILL BE CLOSER TO 20 DEGREES BELOW
NORMAL. THIS WILL RESULT IN TEMPERATURES LARGELY IN THE 70S TO LOW
80S ACROSS THE INTERIOR AND UPPER 50S TO LOW 60S ALONG THE
COASTLINE. THE INTERIOR CENTRAL COAST WILL SEE LOCALLY WARMER
TEMPERATURES IN THE 80S TO LOW 90S. FOR EXAMPLE, THE FORECASTED HIGH
FOR SAN JOSE ON MONDAY IS 75 DEGREES WHILE THE NORMAL HIGH IS 81
DEGREES. THIS PATTERN OF UPPER LEVEL TROUGHING AND COOLER THAN
NORMAL TEMPERATURES IS SET TO CONTINUE THROUGH THE REMAINDER OF THE
LONG TERM FORECAST.
IN ADDITION TO THE RETURN OF BELOW NORMAL TEMPERATURES, ONSHORE
WINDS ARE EXPECTED TO STRENGTHEN ALONG THE COAST, ACROSS MOUNTAIN
RIDGETOPS AND GAPS/PASSES, AND ACROSS THE SAN PABLO/SUISUN BAY AND
DELTA REGION. THIS WILL BRING GUSTS BETWEEN 30 TO 40 MPH ACROSS THE
ABOVE LISTED AREAS WITH HIGHER GUSTS BETWEEN 40 TO 50 MPH POSSIBLE
ACROSS THE EAST BAY HILLS. THE STRONGEST WINDS ARE LIKELY TO BE IN
THE VICINITY OF THE ALTAMONT PASS, AN AREA WHERE TERRAIN FUNNELING
IS COMMON, WITH PROBABILISTIC GUIDANCE SUGGESTING A 10% CHANCE OF
WINDS GUSTING ABOVE 50 MPH. THE AREA OF STRONGEST WINDS WILL
OCCASIONALLY REACH WIND ADVISORY CRITERIA, BUT, THE AREAL EXTENT AND
DURATION IN TIME OF THE WINDS IS TOO SHORT TO NECESSITATE ONE BEING
ISSUED. GUSTY WINDS CONTINUE FROM SUNDAY EVENING THROUGH LATE MONDAY
NIGHT/EARLY TUESDAY MORNING WITH STRONGEST WINDS TAKING PLACE DURING
THE LATE AFTERNOON/EVENING HOURS. SMALL FUELS (E.G. GRASSES) ARE DRY
WITHIN THE EAST BAY HILLS BUT LARGER 100 HOUR FUELS (E.G. SMALLER
TIMBER TYPE VEGETATION)REMAIN FAIRLY MOIST. THIS WILL HELP TO
MITIGATE THE RISK OF LARGER FIRES BUT IF A GRASS FIRE STARTS IN A
FAVORED WIND CORRIDOR IT WILL HAVE THE POTENTIAL TO EXPAND RAPIDLY.
AS SUCH, RESIDENTS OF OR TRAVELERS WITHIN THIS AREA SHOULD EXERCISE
CAUTION IF PARTICIPATING IN ANY OUTDOORS ACTIVITIES INVOLVING FLAMES
(E.G. BARBECUING, CAMPFIRES) AND ENSURE EQUIPMENT IS PROPERLY
SECURED (E.G. TOWING EQUIPMENT) TO PREVENT STRAY SPARKS.
LONG TERM
ISSUED AT 231 PM PDT SUN JUL 20 2025
(MONDAY NIGHT THROUGH NEXT SATURDAY)
GUSTY ONSHORE WINDS WILL CONTINUE THROUGH EARLY TUESDAY MORNING WITH
WINDS CONTINUING TO EASE THROUGHOUT THE REMAINDER OF THE DAY. EXPECT
A RETURN TO OUR TYPICAL DIURNALLY BREEZY PATTERN (GUSTS TO 20 TO 30
MPH) EACH AFTERNOON/EVENING FOR THE COASTLINE AND MOUNTAIN
GAPS/PASSES.
UPPER LEVEL TROUGHING WILL CONTINUE THROUGH THE END OF
THE FORECAST PERIOD WITH BELOW NORMAL TEMPERATURES (70S TO LOW 80S
ACROSS THE INTERIOR AND UPPER 50S TO MID 60S ALONG THE COAST). NO
SKY JULY REMAINS IN FULL SWING WITH WIDESPREAD OVERCAST SKIES,
COASTAL DRIZZLE, AND PATCHY COASTAL FOG TO CONTINUE THIS WEEK. THIS
TROUGH LOOKS TO DEVELOP A CUT-OFF LOW BY MIDWEEK THAT THEN HOVERS
JUST OFFSHORE OF THE BAY AREA. THIS WILL BRING THUNDERSTORM CHANCES
TO OUR NEIGHBORS IN FAR NORTHERN CALIFORNIA AND OREGON, HOWEVER,
THUNDERSTORMS ARE NOT EXPECTED TO DEVELOP WITHIN THE BAY AREA OR IN
THE CENTRAL COAST. ALL IN ALL, NOT TOO MANY CHANGES IN STORE FOR OUR
FORECAST THIS WEEK SO HOPEFULLY YOU HAVE BEEN ENJOYING THE MORE MILD
SUMMER WE HAVE HAD SO FAR.
AVIATION
(18Z TAFS)
ISSUED AT 1105 AM PDT SUN JUL 20 2025
LARGELY A PERSISTENCE FORECAST FOR THE TERMINALS WITH VFR
ANTICIPATED AT MOST SITES (EXCEPT KHAF) THIS AFTERNOON BEFORE MVFR
TO LIFR STRATUS RETURNS THIS EVENING AND INTO THE OVERNIGHT HOURS.
CONFIDENCE IN THE FORECAST IS MEDIUM TO HIGH, THOUGH THERE ARE
THE USUAL NUISANCES DUE TO TERRAIN AND OFFSHORE EDDY FORMATION.
KAPC MAY BE THE BENEFICIARY OF AN EDDY JUST EAST OF THE GG GAP
AND CLEARING WILL BE LATER COMPARED TO SOME OF THE OTHER TERMINALS.
OTHERWISE, ONSHORE FLOW WILL TRANSLATE TO WIND GUSTS NEAR 25
KNOTS AT THE TERMINALS NEAREST THE SF/SAN PABLO BAYS. ONSHORE FLOW
TONIGHT INTO MONDAY WILL USHER IN ANOTHER ROUND OF MARINE STRATUS
AT ALL TERMINALS. THE CURRENT KOAK TAF INDICATES MVFR, AS THE
WINDOW FOR IFR SEEMS TO BE SHORT-LIVED AND CONFIDENCE ISN'T QUITE
HIGH ENOUGH TO INCLUDE, YET. CONFIDENCE IS HIGH THAT BY 0900 UTC,
JUST ABOUT ALL TAFS WILL BE INUNDATED WITH STRATUS. REDUCED
VISIBILITY SHOULD BE ANTICIPATED AT KSTS AND KHAF DUE TO BR/DZ.
WITH THE ONSHORE FLOW REMAINING PERSISTENT, VFR MAY NOT RETURN
UNTIL 1700 UTC OR AFTER AT THE COASTAL TERMINALS.
VICINITY OF SFO...THERE REMAINS AN OPPORTUNITY FOR OCCASIONAL
MVFR CIGS THROUGH 1900 UTC TODAY, BUT THE AFTERNOON WILL LARGELY
BE VFR. WIND GUSTS INCREASE UP TO AROUND 25 KNOTS BY 2100 UTC AND
PERSIST THROUGH THE EARLY EVENING. SOME GUIDANCE (4 OUT OF 10
MODELS) OFFER AN EARLY ONSET OF MVFR STRATUS AND POTENTIAL LOSS OF
VAPS AS EARLY AS 0300 UTC. FOR NOW, WILL LEAN A BIT MORE ON CLIMO
WHICH SUPPORTS MVFR AROUND 0600 UTC. IF MVFR CEILINGS DO ARRIVE
EARLIER, THE EVENING PUSH MAY BE IMPACTED. SIMILAR TO KOAK, THE
CHANCES FOR IFR CIGS IS NON-ZERO, BUT NOT HIGH ENOUGH TO INCLUDE
IN THE TAF AT THIS TIME. IMPACTS TO THE MONDAY MORNING PUSH ARE
HIGHLY PROBABLE WITH MVFR LINGERING THROUGH THE NOONTIME HOUR. THE
CURRENT TAF SET IS A LITTLE PESSIMISTIC ON THE BACK END WITH MVFR
THROUGH MONDAY MID-AFTERNOON, HOWEVER, TRENDS IN SATELLITE AND
MODEL GUIDANCE WILL BE MONITORED FOR REFINEMENTS.
SFO BRIDGE APPROACH...SATELLITE AND WEBCAM IMAGERY SUPPORT VAPS
AND THIS WILL LIKELY CONTINUE THROUGH THE AFTERNOON/EVENING. MVFR
WILL RETURN BETWEEN 0600-0800 UTC WITH ILS OPERATIONS LIKELY
WARRANTED THROUGH AT LEAST LATE MONDAY MORNING.
MONTEREY BAY TERMINALS...STRATUS CONTINUE TO QUICKLY ERODE LATE
THIS MORNING AND VFR SHOULD BE ANTICIPATED THROUGH AT LEAST 00
UTC. NEAR OR SHORTLY AFTER, MVFR/IFR STRATUS WILL RETURN WITH
LIFR CIGS BY 0600 UTC. A FEW INSTANCES OF LIFR AT KSNS ARE
EXPECTED TO TRANSPIRE JUST PRIOR TO 0600 UTC AS FLOW RESPONSES TO
THE DIURNAL HEATING/COOLING ACROSS THE REGION. IFR VISIBILITY IS
ALSO MOST PROBABLE AT KMRY AS CONVERGENCE LEADS TO MEAGER LIFT
ALONG THE MARINE/LAND INTERFACE. VFR DOES NOT APPEAR LIKELY UNTIL
AFTER 1700 UTC MONDAY.
MARINE
(TODAY THROUGH FRIDAY)
ISSUED AT 914 AM PDT SUN JUL 20 2025
MODERATE BREEZES TO NEAR-GALE FORCE WIND GUSTS ARE FORECAST TODAY
AND INTO MONDAY. THIS WILL RESULT IN HAZARDOUS BOATING CONDITIONS
FOR SMALLER VESSELS NEAR AND ACROSS THE NORTHERN SAN FRANCISCO
AND SAN PABLO BAYS. HAZARDOUS BOATING CONDITIONS SHOULD ALSO BE
ANTICIPATED ACROSS NORTHERN OUTER WATERS BEYOND 10 NAUTICAL MILES
FROM THE SHORE. IN ADDITION, NORTHWESTERLY COASTAL JETS WITH
STRONG BREEZES ARE ANTICIPATED THIS AFTERNOON ACROSS NORTHERN
MONTEREY BAY AND NEAR POINT SUR. THESE STRONG BREEZES WILL PERSIST
INTO THE PRE-DAWN HOURS ON MONDAY ACROSS THE BIG SUR COASTLINE.
SLIGHT TO MODERATE SEAS PERSIST THROUGH THE REMAINDER OF THE
FORECAST PERIOD. WINDS EASE SOME THROUGH TUESDAY, EXCEPT ACROSS
SOUTHERN PORTIONS OF THE BIG SUR COAST, WHERE STRONG NORTHWESTERLY
BREEZES PERSIST. OTHERWISE, REDUCED VISIBILITY SHOULD BE
ANTICIPATED DURING THE MORNING HOURS DUE TO FOG/DRIZZLE.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 9 PM PDT MONDAY FOR SF BAY N OF BAY
BRIDGE.
SMALL CRAFT ADVISORY FROM 3 PM TO 9 PM PDT MONDAY FOR MRY BAY-
PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT PIEDRAS
BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 AM PDT MONDAY FOR PT ARENA TO PT
REYES 0-10 NM-PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...BAIN
MARINE...BAIN
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