491
FXUS66 KMTR 010519
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1019 PM PDT MON AUG 31 2026
..NEW AVIATION, MARINE
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
(06Z TAFS)
ISSUED AT 1019 PM PDT MON AUG 31 2026
MVFR STRATUS HAS LINGERED THROUGH THE DAY ACROSS PORTIONS OF THE SF
BAY AREA, AND IS BEGINNING TO EXPAND AGAIN ACROSS THE NORTH BAY AND
INTO THE MONTEREY BAY REGION. HIGH CLOUDS MAY INTERRUPT THE
RADIATIONAL COOLING ACROSS PORTIONS OF THE SOUTH BAY AND CENTRAL
COAST, BUT A VERY DEEP MARINE LAYER SHOULD SUPPORT STRATUS DECKS
HEADING FAR INLAND THROUGH THE COURSE OF THE NIGHT. STRATUS SHOULD
CLEAR BACK TO THE IMMEDIATE COAST THROUGH THE COURSE OF TUESDAY
MORNING INTO THE EARLY AFTERNOON, WITH A GENTLE TO MODERATE ONSHORE
PATTERN WIND DEVELOPING IN THE AFTERNOON AND EVENING HOURS. TUESDAY
NIGHT, LOWER CONFIDENCE IN STRATUS IMPACTS AS THE FRINGES OF A
DECAYING FRONT BEGIN TO IMPACT THE REGION, WITH A SHIFT TO A MORE
SOUTHWEST WIND FLOW EXPECTED AS THE FRONT OR ITS REMNANTS APPROACH.
CHANCES FOR RAIN IN THE NORTH BAY LIE JUST AFTER THE END OF THE 24-
HOUR TAF PERIOD.
VICINITY OF SFO... MVFR STRATUS WITH GENTLE SOUTHWEST WINDS THROUGH
THE NIGHT AND INTO TUESDAY MORNING. MODERATE CONFIDENCE IN A
MODERATE WESTERLY BREEZE DEVELOPING IN THE AFTERNOON AND EVENING
HOURS ON TUESDAY, WITH WINDS TURNING TO THE SOUTHWEST AND THE SOUTH
THROUGH THE EVENING AND OVERNIGHT PERIODS. LOW CONFIDENCE OF MVFR
CEILINGS TUESDAY NIGHT BEFORE THE END OF THE TAF PERIOD, WITH
GREATER CONFIDENCE IN LOW-END VFR CLOUDS OVER THE TERMINAL.
SFO BRIDGE APPROACH... SIMILAR TO SFO.
MONTEREY BAY TERMINALS... MVFR TO LOW-END VFR CEILINGS PERSIST
THROUGH THE LATTER PART OF TUESDAY MORNING. A GENTLE ONSHORE WIND
PERSISTS THROUGH THE AFTERNOON AND EVENING, WITH THE WINDS TURNING
FROM THE SOUTHWEST OVER MRY TONIGHT TO THE WEST FOR THE AFTERNOON
AND EVENING. LOW CONFIDENCE IN A RETURN OF STRATUS TO SNS TUESDAY
NIGHT AS WINDS DIMINISH.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 1019 PM PDT MON AUG 31 2026
GENTLE WESTERLY TO NORTHWESTERLY BREEZES PERSIST THROUGH THE WEEK
WITH INTERMITTENT PERIODS OF MODERATE BREEZES. WIND DRIVEN SEAS
REMAIN SLIGHT TO MODERATE THROUGH THE WEEK WITH LONG PERIOD
SOUTHERLY SWELLS PERSISTING THANKS TO TROPICAL CYCLONE ACTIVITY.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PDT TUESDAY FOR SF BAY N OF BAY
BRIDGE.
SHORT TERM...SARMENT
LONG TERM....SARMENT
AVIATION...DIALH
MARINE...DIALH
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