942
FXUS66 KMTR 220148
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
648 PM PDT THU MAY 21 2026
..NEW UPDATE
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
(00Z TAFS)
ISSUED AT 445 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 TERMINALS WITH
THE EXCEPTION OF THE INTERIOR TERMINALS OF LVK AND SJC.
UNCERTAINTY LIES IN THE DEPTH OF THE MARINE LAYER. CURRENTLY
SHALLOW AT AROUND 500 FEET, IT IS EXPECTED TO DEEPEN TO 1,000 FEET
TONIGHT WITH AN APPROACHING SURFACE TROUGH. THIS WOULD TYPICALLY
LIFT CEILINGS; HOWEVER, THE MOIST SOUTHWESTERLY FLOW AHEAD OF IT MAY
LEAD TO FOG FORMATION WITH THE COASTAL TERMINALS AT GREATEST
RISK. DIURNAL WINDS WILL PREVAIL.
VICINITY OF SFO...CURRENTLY VFR WITH NORTHWESTERLY FLOW. MODERATE
CONFIDENCE (40%) ON A SUB-VFR CEILING DEVELOPING AT THE TERMINAL,
LIKELY ON THE CUSP OF IFR/MVFR. DIURNAL WINDS WILL PREVAIL.
SFO BRIDGE APPROACH...LOW CLOUDS ARE EXPECTED TO BEGIN IMPACTING THE
SAN MATEO BRIDGE APPROACH TONIGHT AS EARLY AS 04Z. AS THEY COME
THROUGH THE GOLDEN GATE GAP, THEY WILL MAKE CONTACT WITH THE EAST
BAY HILLS AND THEN SPREAD NORTH AND SOUTH; THUS, LOW CLOUD PROBABILITIES
ARE HIGHER FOR THE EAST BAY AND OAK WITH ONLY MODERATE CONFIDENCE
(45%) BETWEEN SJC AND SFO.
MONTEREY BAY TERMINALS...CURRENTLY VFR WITH WESTERLY FLOW AT MRY AND
MVFR WITH NORTHWESTERLY FLOW AND HAZE AT SNS. HIGH CONFIDENCE ON
LIFR CONDITIONS RETURNING TO BOTH TERMINALS TONIGHT WITH FOG
POSSIBLE. VFR IS EXPECTED BY LATE MORNING WITH IFR STRATUS
STICKING CLOSE TO THE COAST DURING THE DAY.
MARINE
(TONIGHT THROUGH NEXT TUESDAY)
ISSUED AT 445 PM PDT THU MAY 21 2026
FRESH TO STRONG NORTHERLY WINDS AND MODERATE SEAS CONTINUE ACROSS
THE FAR NORTHERN OUTER WATERS THROUGH EARLY FRIDAY MORNING. WINDS
DIMINISH TO MODERATE TO FRESH WITH OCCASIONAL STRONG GUSTS FRIDAY
INTO SATURDAY. ELSEWHERE, A MODERATE BREEZE AND MODERATE SEAS
CONTINUE INTO THE WEEKEND. CONDITIONS FURTHER IMPROVE SUNDAY INTO
EARLY NEXT WEEK WITH A GENTLE TO MODERATE BREEZE EXPECTED OVER THE
COASTAL WATERS. UNSETTLED WEATHER RETURNS MID TO LATE WEEK WITH
STRENGTHENING WINDS AND BUILDING SEAS.
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...KENNEDY
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