836
FXUS66 KMTR 311954
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1254 PM PDT MON AUG 31 2026
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 1250 PM PDT MON AUG 31 2026
- WELL BELOW NORMAL TEMPERATURES THROUGH FRIDAY, GRADUAL WARMING
AND DRYING TREND THIS WEEKEND
- BENEFICIAL WETTING RAIN IN THE NORTH BAY TUESDAY THROUGH
THURSDAY, DRIZZLE/LIGHT RAIN POSSIBLE ELSEWHERE
SHORT TERM
ISSUED AT 1250 PM PDT MON AUG 31 2026
(MONDAY THROUGH FRIDAY)
UPPER-LEVEL SHORTWAVE TROUGHING WILL SWING INTO NORTHERN CALIFORNIA
TOMORROW; THIS WILL RESULT IN TEMPERATURES WELL BELOW NORMAL, A
CHANCE FOR DRIZZLE/LIGHT RAIN, AND WIDESPREAD CLOUD COVER. THE BEST
CHANCES FOR DRIZZLE/LIGHT RAIN WILL BE IN THE NORTH BAY,
PARTICULARLY ALONG THE COAST AND IN THE HIGHER TERRAIN WITH THE HELP
OF OROGRAPHIC LIFT. A REINFORCING UPPER-LEVEL LOW AND AN ATTENDANT
COLD FRONT WILL APPROACH THE AREA WEDNESDAY INTO THURSDAY. THIS WILL
KEEP WELL BELOW NORMAL TEMPERATURES AND CLOUDY CONDITIONS AROUND AND
LIKELY MAKE THE MARINE LAYER ARBITRARY. THERE WILL BE A BETTER
CHANCE FOR DRIZZLE/LIGHT RAIN WITH THIS ROUND WITH A LIFTING
MECHANISM IN PLACE AS PWAT CLIMBS TO NEAR ONE INCH (90TH
PERCENTILE). IT IS LIKELY (60+% CHANCE) THAT THE NORTHWESTERN HALF
OF THE NORTH BAY GETS WETTING RAIN (0.10 INCHES) BETWEEN NOW AND
THEN. WHILE RAINFALL IS EXPECTED TO BE BENEFICIAL, WET ROADWAYS WILL
CREATE SLICK DRIVING CONDITIONS AND INCREASE STOPPING DISTANCE.
LONG TERM
ISSUED AT 1250 PM PDT MON AUG 31 2026
(SATURDAY THROUGH SUNDAY)
GLOBAL ENSEMBLE CLUSTERS DIVERGE ON SOLUTIONS DRAMATICALLY GOING
INTO THE WEEKEND, SPECIFICALLY ON LOW VS TROUGH AND THE LOCATION AND
TIMING OF THE FEATURE, SO BASICALLY EVERYTHING. WHAT IS CERTAIN IS
THAT THE REGION WILL BE UNDER THE INFLUENCE OF SOME KIND OF
TROUGHING THROUGH THE WEEKEND. AS IT WEAKENS THROUGH THE WEEKEND, A
GRADUAL WARMING AND DRYING TREND WILL COMMENCE WITH TEMPERATURES
MODERATING TO SLIGHTLY BELOW TO NEAR NORMAL. BEYOND THE SEVEN DAY
FORECAST AND INTO LABOR DAY/EARLY NEXT WEEK, INVEST EP95 WELL
OFFSHORE OF SOUTHWESTERN MEXICO BECOMES A VARIABLE. UNCERTAINTY OVER
THE WEEKEND WILL COMPOUND AND PROPAGATE INTO THE TROPICAL SIDE OF
THE FORECAST, MAKING IT IMPOSSIBLE TO TALK SPECIFIC IMPACTS AT THIS
POINT IN TIME. THE PRIMARY IMPACTS WOULD LIKELY BE RAIN AND WIND
WITH IMPACTS LIKELY DECREASING FROM SOUTH TO NORTH.
AVIATION
(18Z TAFS)
ISSUED AT 1156 AM PDT MON AUG 31 2026
FINISHING FOGUST OFF STRONG WITH A ROBUST MARINE LAYER AT A DEPTH OF
AROUND 2200 FEET THIS MORNING. MVFR STRATUS WILL TAKE A BIT LONGER
TO SCATTER OUT TODAY, LIKELY IN THE EARLY AFTERNOON. MODERATE
ONSHORE WINDS INCREASE THROUGH THE DAY AND EASE SLIGHTLY OVERNIGHT.
APC AND LVK MAY EXPERIENCE GUSTS UP TO 20 KT THROUGH THE LATE
AFTERNOON WHICH WILL GRADUALLY DIMINISH TONIGHT. MEDIUM CONFIDENCE
ON HOW WIDESPREAD THE MARINE LAYER WILL BE TONIGHT AS AN UPPER LEVEL
TROUGH APPROACHES OUR COAST. THIS TROUGH MAY GENERATE SUFFICIENT
LIFTING TO MIX OUT THE MARINE LAYER ACROSS THE NORTH BAY, BUT
CONFIDENCE REMAINS LOW. HIGHER CONFIDENCE FOR COASTAL SITES TO
DEVELOP MVFR CEILINGS AROUND SUNSET WITH HAF LIKELY TO STAY CLOUDY
ALL DAY.
VICINITY OF SFO...MVFR STRATUS PERSISTS INTO THE AFTERNOON AS
MODERATE WESTERLY WINDS INCREASE. THERE HAS BEEN SOME DISAGREEMENT
IN THE MODEL GUIDANCE ON WHETHER STRATUS WILL COMPLETELY SCATTER OUT
TODAY. CURRENTLY ON SATELLITE, THERE IS SOME DRY AIR MAKING ITS WAY
TO OUR COAST. THIS DRY AIR COMBINED WITH A MODERATE ONSHORE FLOW
MAY BE ENOUGH TO SCATTER OUT THE REMAINING CLOUDS IN THE SF BAY.
MVFR CEILINGS RETURN AS WINDS EASE TO GENTLE AND PERSIST INTO
TUESDAY AFTERNOON. MEDIUM CONFIDENCE ON THE OVERALL FORECAST.
SFO BRIDGE APPROACH...STRATUS IS LIKELY TO BECOME PATCHY OVER THE
BRIDGE BEFORE SCATTERING OUT AT THE TERMINALS THIS
MORNING/EARLY AFTERNOON. OTHERWISE, SIMILAR TO SFO.
MONTEREY BAY TERMINALS...NORTHWEST TO WESTERLY BREEZES INCREASE TO
MODERATE THIS AFTERNOON AS MVFR CEILINGS SCATTER OUT. THE MARINE
LAYER IS LESS LIKELY TO MIX OUT DUE TO THE UPPER LEVEL TROUGH,
THEREFORE ANTICIPATE AN EARLY RETURN OF MVFR CEILINGS RIGHT
AROUND SUNSET.
MARINE
(TODAY THROUGH SATURDAY)
ISSUED AT 1156 AM PDT MON AUG 31 2026
NORTHWEST TO WESTERLY GENTLE BREEZES PREVAIL THROUGH THE WEEK AND
MAY BECOME MODERATE AT TIMES. WIND DRIVEN SEAS REMAIN SLIGHT TO
MODERATE THROUGH THE WEEK AS A LONG PERIOD SOUTHERLY SWELL
CONTINUES TO DIMINISH BY TUESDAY.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT TUESDAY FOR SF BAY N OF BAY
BRIDGE.
SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR MRY BAY.
SHORT TERM...SARMENT
LONG TERM....SARMENT
AVIATION...NAVARRETE
MARINE...NAVARRETE
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