175
FXUS66 KMTR 211935
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1235 PM PDT THU MAY 21 2026
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 1234 PM PDT THU MAY 21 2026
- DIURNALLY DRIVEN ONSHORE WINDS DURING THE AFTERNOON AND EARLY
EVENING
- WARM AND DRY WEATHER THROUGH FRIDAY LEADS TO ELEVATED FIRE
WEATHER CONCERNS FOR THE INTERIOR BAY AREA AND CENTRAL COAST
- GRADUAL COOLING TREND BEGINS FRIDAY WITH SEASONAL TEMPERATURES
FOR THE UPCOMING WEEKEND
SHORT TERM
ISSUED AT 1234 PM PDT THU MAY 21 2026
(THIS EVENING THROUGH FRIDAY)
TODAY WE CONTINUE TO SEE DRY CONDITIONS ACROSS THE INTERIOR AND
WITH AFTERNOON MAXIMUM TEMPERATURES REACHING THE LOWER 80S TO
LOWER 90S UNDER SUNNY SKIES. MEANWHILE, THE COAST WILL STAY COOLER
THANKS THE ~1000 FT MARINE LAYER WHERE WE ARE EXPECTING THE UPPER
50S TO MIDDLE 60S. WITH THE LARGE SCALE PATTERN ALOFT IS DEFINED
BY A THROUGH OVER THE NORTHERN ROCKY MOUNTAINS AND A BUILDING
RIDGE OVER THE NORTHEASTERN PACIFIC. THIS PATTERN LARGELY SUPPORTS
ONSHORE WINDS AT THE SURFACE WITH COASTAL BREEZES DEVELOPING EACH
AFTERNOON AND EVENING.
TONIGHT, EXPECT THE MARINE LAYER TO REMAIN STEADY, YET THE INLAND
EXTEND IS LIKELY TO INCREASE INTO THE COASTAL ADJACENT VALLEYS
EARLY FRIDAY MORNING. HOWEVER, SIMILAR TO TODAY, THESE LOW CLOUDS
WILL QUICKLY RETREAT TO THE COASTLINE BY LATE MORNING.
FRIDAY WE ARE EXPECTING A SLIGHT COOL DOWN IN AFTERNOON
TEMPERATURES AS THE TROUGH SHIFTS EASTWARD ALLOWING FOR A DEEPER
MARINE LAYER TO RETURN. COASTAL AREAS ARE LIKELY TO REMAIN IN THE
UPPER 50S TO MIDDLE 60S WITH THE INTERIOR WARMING INTO THE UPPER
70S TO MIDDLE 80S. THE ONLY FAR INTERIOR AREAS LIKE PINNACLES
NATIONAL PARK, KING CITY, SAN LUCAS, AND SAN ARDO HAVE THE
POTENTIAL TO REACH 90 DEG F.
LONG TERM
ISSUED AT 1234 PM PDT THU MAY 21 2026
(FRIDAY NIGHT THROUGH NEXT WEDNESDAY)
THE COOLING TREND WILL CONTINUE INTO THIS UPCOMING WEEKEND WITH
TEMPERATURES RETURNING TO NEAR SEASONAL AVERAGES. THIS IS AS THE
MARINE LAYER IS FORECAST TO DEEPEN TO ~1500 FT. CANNOT RULE OUT
LATE EVENING AND EARLY MORNING COASTAL DRIZZLE DURING THIS
TIMEFRAME AS THE BOUNDARY LAYER REMAINS VERY MOIST.
BY LATE MONDAY AND EARLY TUESDAY, A FRONTAL BOUNDARY IS FORECAST
TO SWEEP ACROSS THE REGION. THIS WOULD BRING THE POTENTIAL FOR
DRIZZLE AND/OR LIGHT RAIN AS THE FRONT MOVES FROM NORTH TO SOUTH
ACROSS THE BAY AREA AND CENTRAL COAST. IN WAKE OF THE FRONTAL
PASSAGE, THE MARINE LAYER MAY MIX OUT AND ALLOW FOR COASTAL
LOCATIONS SLIGHTLY WARMER COMPARED TO THIS WEEKEND.
AVIATION
(18Z TAFS)
ISSUED AT 1107 AM PDT THU MAY 21 2026
CLEAR SKIES ACROSS THE INTERIOR WITH AN EXPANSIVE STRATUS DECK ALONG
THE COAST. KEPT HAF OVERCAST THROUGHOUT THE DAY BUT A BRIEF PERIOD
OF CLEARING IS LIKELY FOR MRY AND SNS. CURRENT THINKING IS THAT THE
MARINE LAYER WILL DEEPEN TO AROUND 1000 FT TONIGHT WITH A MIX OF IFR
TO MVFR STRATUS ACROSS THE INTERIOR. LIFR AND FOG IS EXPECTED
DIRECTLY ALONG THE COASTLINE WITH FOG POTENTIAL INCREASING BY EARLY
TOMORROW MORNING. CLEARING IS EXPECTED BY LATE TOMORROW
MORNING/EARLY AFTERNOON.
VICINITY OF SFO...WINDS STRENGTHEN TO AROUND 17 KNOTS THIS
AFTERNOON/EVENING BEFORE EASING OVERNIGHT. MODERATE CONFIDENCE THAT
MVFR CIGS WILL REACH SFO AROUND 10Z WITH SOME POTENTIAL FOR CIGS TO
BRIEFLY DROP BELOW 1000 FT. IT IS WORTH NOTING THAT THE HRRR SHOWS A
"DONUT HOLE" DEVELOPING OVER SFO THIS MORNING STRATUS FILTERS IN
THROUGH THE GOLDEN GATE GAP AND FILLS INTO THE EAST BAY/SF BAY BUT
DOES NOT REACH SFO. CONFIDENCE IS SLIGHTLY HIGHER THAT A CIG WILL
REACH SFO OVERNIGHT BUT IT IS WORTH NOTING THEIR IS SOME POTENTIAL
FOR CONDITIONS TO REMAIN VFR OVERNIGHT.
SFO BRIDGE APPROACH...MVFR TO IFR CIGS ARE LIKELY TO DEVELOP OVER
THE SF BAY OVERNIGHT WITH CLEARING BY LATE TOMORROW MORNING.
MONTEREY BAY TERMINALS...CIGS HAVE CLEARED FROM MRY AND SNS WITH A
BRIEF PERIOD OF VFR EXPECTED THROUGH 01/02Z. GIVEN THE EXPANSIVE
STRATUS DECK JUST OFFSHORE, OPTED TO PUSH THE ARRIVAL OF STRATUS
EARLIER IN THE TAF. CONFIDENCE INCREASES IN STRATUS RETURNING AROUND
01/02Z BUT IT MAY RETURN EARLIER IF ANOTHER EDDY DEVELOPS WITHIN THE
BAY. GENERALLY EXPECTING FOG CHANCES TO INCREASE EARLY TOMORROW
MORNING, PARTICULARLY AT SNS BUT WOULD NOT RULE OUT PATCHY FOG
IMPACTING MRY. BREEZY ONSHORE WINDS DURING THE AFTERNOON/EVENING
WILL WEAKEN OVERNIGHT, BECOMING LIGHT TO VARIABLE.
MARINE
(TODAY THROUGH TUESDAY)
ISSUED AT 945 AM PDT THU MAY 21 2026
FRESH TO STRONG NORTHERLY WINDS CONTINUE ACROSS THE FAR NORTHERN
OUTER WATERS, RESULTING IN HAZARDOUS CONDITIONS AND ROUGH SEAS
THROUGH THURSDAY. MODERATE NORTHWESTERLY BREEZES AND MODERATE SEAS
WILL PREVAIL FOR THE REST OF THE WATERS. CONDITIONS IMPROVE INTO
THE WEEKEND AS SEAS AND NORTHWESTERLY BREEZES BECOME MODERATE WITH
THE OCCASIONAL FRESH TO STRONG BREEZE POSSIBLE ACROSS THE FAR
NORTHERN OUTER WATERS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT FRIDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...RGASS
LONG TERM....RGASS
AVIATION...KENNEDY
MARINE...KENNEDY
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