095
FXUS66 KMTR 010849
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
149 AM PDT FRI MAY 1 2026
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 223 PM PDT THU APR 30 2026
- WARMING AND DRYING TREND CONTINUES TOMORROW FOR AREAS AWAY
FROM THE COAST
- OVERNIGHT AND EARLY MORNING STRATUS REMAINS IN THE FORECAST AS
THE MARINE LAYER DEEPENS INTO THE WEEKEND
- COOLER CONDITIONS THIS WEEKEND WITH A CHANCE OF DRIZZLE AND/OR
LIGHT RAIN INTO EARLY NEXT WEEK
SHORT TERM
ISSUED AT 149 AM PDT FRI MAY 1 2026
(TODAY AND TONIGHT)
STEADY AND COOL NORTHWEST WINDS CONTINUE OVER THE COASTAL WATERS
WITH SEA SURFACE TEMPERATURES VARYING FROM 54F TO 59F (~ 2F TO 3F
ABOVE MAY NORMALS). COASTAL STRATUS CONTINUES TO DEVELOP WITH AN
INLAND INTRUSION TAKING PLACE PER SATELLITE AND SURFACE OBSERVATIONS.
A LOWER TO MID LEVEL THERMAL RIDGE IS CAPPING STRATUS CLOUDS
WHILE A CLEAR SKY ABOVE IS ALLOWING NOCTURNAL RADIATIVE COOLING.
CURRENTLY, A 500 MB HEIGHT RIDGE EXTENDS FROM THE EASTERN PACIFIC
TO NORTHERN CALIFORNIA, THE PACIFIC NORTHWEST, ALBERTA AND
SASKATCHEWAN. AIR TEMPERATURES CURRENTLY VARY FROM THE MID 40S TO
50S IN THE LOWER ELEVATIONS TO THE 60S IN THE HIGHER ELEVATIONS,
WHERE IT'S MILDER WITHIN THE LOWER LEVEL TEMPERATURE INVERSION.
STRATUS CLOUDS WILL CLEAR TO THE COASTLINE UNDER PEAK DIURNAL
MIXING LATER TODAY. DAYTIME HIGHS WILL CLIMB A FEW DEGREES ABOVE
EARLY MAY NORMALS INLAND TO NEAR NORMAL ALONG THE IMMEDIATE COAST.
HIGH TEMPERATURES WILL VARY FROM THE 60S COASTSIDE, 70S BAYSIDE
TO THE LOWER TO MID 80S FAR INLAND. TONIGHT, THE AFOREMENTIONED
500 MB RIDGE WILL SHIFT EASTWARD AND WEAKEN ALLOWING FOR COOLING
ALOFT TO COMMENCE. COASTAL STRATUS REDEVELOPMENT AND ONSHORE BREEZES
WILL POTENTIALLY USHER STRATUS FARTHER INLAND TONIGHT AND SATURDAY
MORNING.
LONG TERM
ISSUED AT 149 AM PDT FRI MAY 1 2026
(SATURDAY THROUGH THURSDAY)
AN EASTWARD MOVING 500 MB OPEN WAVE TROUGH APPROACHING THE PACIFIC
NORTHWEST WILL CLOSE OFF BY LATE TODAY. BEHIND THE 500 MB TROUGH A
SHARPENING 500 MB RIDGE WILL BECOME UNSTABLE, FURTHER SUPPORTING
THE CLOSING OFF 500 MB LOW. THIS OFTEN HAPPENS WHEN POLAR JET
STREAM WINDS ARE UNABLE TO FOLLOW SHARP 500 MB RIDGE CONTOURS,
FIRST HEADING EASTWARD THEN FLOWING BACK WESTWARD, CARVING OUT AND
CLOSING OFF A 500 MB LOW TO THE SOUTH. THIS 500 MB LOW WILL MOVE
SOUTH WHILE THE 500 MB RIDGE ALSO CLOSES OFF TO THE NORTH, FORMING
A REX BLOCK PATTERN OVER THE WEEKEND AND EARLY NEXT WEEK. DYNAMIC
COOLING ALOFT WITH LOWERING 500 MB HEIGHTS OVER OUR AREA WILL
DEEPEN THE MARINE LAYER, WITH FURTHER COOLING TAKING PLACE AND
POTENTIALLY PRODUCING PERIODIC LIGHT DRIZZLE AND/OR LIGHT RAIN.
IT'S A LOW CONFIDENCE FORECAST IN TERMS OF HOW MUCH PRECIPITATION
MAY RESULT. AT THE MOMENT IT DOES NOT LOOK LIKE VERY MUCH I.E. UP
TO A FEW HUNDREDTHS; MODEL FORECASTS ARE VARYING IN SOLUTIONS. STAY
TUNED TO UPDATES.
THE REX BLOCK IS NOT FORECAST TO LAST VERY LONG, IT'S LIKELY TO
BEGIN WEAKENING AND BREAKING DOWN BY THE MIDDLE OF NEXT WEEK. THE
SUBTROPICAL JET STREAM ATTACHES TO THE BASE OF THE CLOSED 500 MB
LOW OVER THE WEEKEND AND EARLY NEXT WEEK ASSISTING WITH EJECTING
THE LOW EASTWARD MID TO LATE NEXT WEEK. BTW, THE STRENGTH OF THE
SUBTROPICAL JET STREAM IS LIKELY IN RESPONSE TO RECENT SURFACE
WATER WARMING OVER LOWER LATITUDES. THE 500 MB LOW GETTING PICKED
UP BY THE SUBTROPICAL JET STREAM ALLOWS THE POLAR JET STREAM OVER
THE PACIFIC TO HELP MOVE THINGS ALONG TO THE EAST AS WELL, USHERING
IN A NEWLY ARRIVING 500 MB MID-LATITUDE TROUGH WITH THE POTENTIAL
FOR SHOWERY WEATHER OVER NORTHERN CALIFORNIA LATE NEXT WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 1004 PM PDT THU APR 30 2026
NO MAJOR CHANGES TO THE FORECAST AS STRATUS CONTINUES TO SLITHER
INTO THE REGION. CIGS WILL GENERALLY BE AROUND MVFR LEVELS, WITH THE
POTENTIAL FOR IFR ALONG THE COAST AND PERHAPS INTO THE NORTH BAY
VALLEYS EARLY TOMORROW MORNING. CIGS ARE EXPECTED TO CLEAR BY MID TO
LATE MORNING, WITH VFR CONDITIONS RETURNING FOR THE AFTERNOON AND
EARLY EVENING HOURS. THOUGH STRATUS WILL RETURN TOMORROW EVENING.
MEDIUM TO HIGH CONFIDENCE IN THIS FORECAST.
VICINITY OF SFO...THE STRATUS ARRIVED A BIT EARLIER THAN EXPECTED
BASED ON THE LAST SET OF TAFS, WITH MVFR CIGS HOLDING OVER THE
TERMINAL. WINDS HAVE BEGUN TO EASE AND SHOULD DROP TO LESS THAN 10KT
OVER THE NEXT FEW HOURS. EXPECT CONDITIONS TO BEGIN CLEARING BETWEEN
15-18Z, WITH CIGS COMPLETELY CLEARING BETWEEN 18-20Z. TOMORROW
AFTERNOON, ANOTHER ROUND OF BREEZY WESTERLY WINDS ARE EXPECTED.
STRATUS SHOULD RETURN BETWEEN 00-03Z SATURDAY. MEDIUM TO HIGH
CONFIDENCE IN THIS FORECAST.
SFO BRIDGE APPROACH...SIMILAR TO SFO. MVFR CIGS SHOULD COVER THE A
PORTION OF THE BAY THIS EVENING AND MAY FILL IN THE SOUTHERN HALF OF
THE SAN FRANCISCO BAY TONIGHT. CLOUDS MAY CLEAR A BIT FASTER THAN
KOAK AND KSFO IN THE MORNING. LOW TO MEDIUM CONFIDENCE.
MONTEREY BAY TERMINALS...JUST WHEN YOU THINK YOU HAVE A HANDLE ON
THE STRATUS, IT THROWS YOU A CURVE BALL. WITH THAT BEING SAID, MVFR
CIGS HUG KMRY DOWN TO BIG SUR AND FLIRT AROUND KSNS THIS EVENING.
THE BEST GUIDANCE THAT CAPTURES THIS IS THE HREF AND NAMNEST, WITH
KSNS SEEING MVFR CIGS RETURN AROUND 09Z. THERE IS SOME UNCERTAINTY
IF WE'LL ACTUALLY HIT IFR CONDITIONS AT KMRY AND KSNS, WITH KMRY
HAVING THE BETTER CHANCES. OPTED TO KEEP THE CIGS AROUND OVC007
THERE AND PUT KSNS AT OVC010 INSTEAD. CLEARING BEGINS BY MID TO LATE
MORNING, WITH VFR CIGS EXPECTED FOR THE AFTERNOON. STRATUS RETURNS
ONCE AGAIN LATE TOMORROW AFTERNOON AND INTO THE EARLY EVENING.
MEDIUM TO HIGH CONFIDENCE IN THIS FORECAST.
MARINE
(TONIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 903 PM PDT THU APR 30 2026
FRESH TO STRONG NORTHWEST BREEZES WILL CONTINUE INTO SATURDAY WITH
WINDS BECOMING MODERATE TO FRESH BY SUNDAY. WINDS WILL BE
STRONGEST OVER THE NORTHERN OUTER WATERS WHERE WINDS WILL RESULT
IN MODERATE SEAS BUILDING TO BETWEEN 10 TO 12 FEET. WITH EASING
WINDS, SEAS WILL BEGIN SUBSIDE BY LATE SATURDAY WITH CONDITIONS
IMPROVING THROUGH THE REMAINDER OF THE WEEKEND.
MTR WATCHES/WARNINGS/ADVISORIES
CA...BEACH HAZARDS STATEMENT FROM SATURDAY MORNING THROUGH SUNDAY
EVENING FOR CAZ006-505-509-529-530.
PZ...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PDT THIS
EVENING FOR PT ARENA TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 AM PDT SATURDAY FOR PT ARENA TO PT
REYES 10-60 NM.
SHORT TERM...CANEPA
LONG TERM....CANEPA
AVIATION...KR
MARINE...KR
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