567
FXUS66 KMTR 220440
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
940 PM PDT THU MAY 21 2026
..NEW AVIATION, MARINE
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
UPDATE
ISSUED AT 643 PM PDT THU MAY 21 2026
STRATUS CONTINUES TO IMPACT THE IMMEDIATE COAST WITH SOME INLAND
EXPANSION ACROSS THE MONTEREY BAY REGION, AND A FINGER OF STRATUS
COMING THROUGH THE GOLDEN GATE INTO THE BERKELEY AREA. THE BODEGA
BAY PROFILER IS REPORTING A MARINE LAYER DEPTH OF AROUND 1000 TO
1500 FT, WHICH IS CONDUCIVE TO EXPANDED STRATUS DEVELOPMENT INTO
THE INLAND VALLEYS THROUGH THE EARLY HOURS OF FRIDAY MORNING.
DIALH
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
EXTENT 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
(06Z TAFS)
ISSUED AT 938 PM PDT THU MAY 21 2026
CURRENTLY A MIXED BAG OF LIFR-VFR AT THE TERMINALS. MODERATE TO HIGH
CONFIDENCE ON IFR-LIFR CONDITIONS RETURNING TO ALL THE TERMINALS
TONIGHT WITH THE EXCEPTION OF THE INTERIOR TERMINALS OF LVK AND SJC.
DIURNAL WINDS WILL PREVAIL.
VICINITY OF SFO...CURRENTLY VFR WITH NORTHWESTERLY FLOW. STRATUS IS
CURRENTLY BEING HELD OFF JUST TO THE NORTHWEST OF THE TERMINAL.
MODERATE CONFIDENCE ON THIS REACHING THE TERMINAL, LIKELY AROUND
09Z. DIURNAL WINDS WILL PREVAIL.
SFO BRIDGE APPROACH...LOW CLOUDS COMING IN THROUGH THE GOLDEN GATE
GAP WILL CONTINUE TO SPREAD SOUTH ALONG THE EAST BAY SHORELINE
TONIGHT WITH THE SAN MATEO BRIDGE APPROACH LIKELY TO BE IMPACTED
THROUGH LATE MORNING.
MONTEREY BAY TERMINALS...CURRENTLY IFR WITH SOUTHWESTERLY FLOW AT
MRY AND IFR WITH NORTHWESTERLY FLOW AT SNS. HIGH CONFIDENCE ON
CONDITIONS DETERIORATING TO LIFR WITH FOG POSSIBLE. VFR IS EXPECTED
BY LATE MORNING WITH IFR STRATUS STICKING CLOSE TO THE COAST
DURING THE DAY. ANOTHER EARLY RETURN OF STRATUS IS EXPECTED
TOMORROW NIGHT.
MARINE
(TONIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 938 PM PDT THU MAY 21 2026
HAZARDOUS CONDITIONS FOR SMALL CRAFT CONTINUE TONIGHT FOR THE
NORTHERN OUTER WATERS DUE TO STRONG NORTHERLY BREEZES AND ROUGH
SEAS. MODERATE NORTHWESTERLY BREEZES WILL BACK TO BECOME
SOUTHWESTERLY TOMORROW AND PREVAIL THROUGH THE WEEKEND. ROUGH
WATERS ARE EXPECTED ACROSS THE NORTHERN OUTER WATERS FRIDAY WITH
WIDESPREAD MODERATE SEAS PREVAILING SATURDAY THROUGH MONDAY.
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...SARMENT
MARINE...SARMENT
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