424
FXUS66 KMTR 010558
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1058 PM PDT MON AUG 31 2026
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 1039 PM PDT MON AUG 31 2026
- COOLER WEATHER CONTINUES THROUGH THE WEEK
- BENEFICIAL WETTING RAIN EXPECTED IN THE NORTH BAY
SHORT TERM
ISSUED AT 1039 PM PDT MON AUG 31 2026
(TONIGHT THROUGH WEDNESDAY)
COOL AND WET. A DEEP 500 MB TROUGH WILL SLOWLY MOVE TOWARDS THE
COAST OVER THE NEXT 24 HOURS. THE MARINE LAYER IS CURRENTLY 3,200
FT DEEP AS MEASURED BY THE 00Z OAK SOUNDING. THIS DEEP MARINE
LAYER, COMBINED WITH THE APPROACHING TROUGH, WILL VERY LIKELY
BRING SOME COASTAL DRIZZLE TUESDAY MORNING. AFTERNOON
TEMPERATURES WILL BE 5-15 DEGREES BELOW NORMAL AS THE 850 MB
TEMPERATURE DROPS BELOW 10C/50F FOR THE FIRST TIME SINCE MAY. BY
TUESDAY NIGHT A VERY WEAK COLD FRONT WILL BRING A GOOD CHANCE FOR
LIGHT RAIN TO THE NORTH BAY. THIS FRONT WILL MOVE SOUTHWARD
THROUGH THE NIGHT AND INTO WEDNESDAY MORNING, BRINGING LOWER RAIN
CHANCES TO THE REST OF THE BAY AREA AND CENTRAL COAST. WEDNESDAY
WILL BE SIMILAR TO TUESDAY WITH COOL TEMPERATURES AND ANOTHER
CHANCE FOR RAIN IN THE NORTH BAY OVERNIGHT AS A SECOND DISTURBANCE
MOVES THROUGH.
LONG TERM
ISSUED AT 1039 PM PDT MON AUG 31 2026
(WEDNESDAY NIGHT THROUGH NEXT MONDAY)
RAIN CHANCES PEAK THURSDAY MORNING WITH AN 90% CHANCE OF
PRECIPITATION IN THE NORTH BAY, AND A 70% CHANCE OF AT LEAST
1/10" AT SANTA ROSA. AGAIN THE RAIN CHANCES FALL OFF QUICKLY AS
THE SYSTEM MOVES SOUTH, BUT THERE'S A DECENT CHANCE (20-50%) FOR
LIGHTER RAIN ACROSS THE CWA. THE COOLER WEATHER WILL CONTINUE
THROUGH FRIDAY AS THE TROUGH PRODUCES A CUT-OFF LOW NEAR THE
PACIFIC NORTHWEST. BY THE WEEKEND, HIGH PRESSURE WILL BUILD OVER
THE DESERT SW. THE INTERACTION BETWEEN THE LOW PRESSURE TO THE NW
AND HIGH PRESSURE TO THE SE BRINGS MORE UNCERTAINTY TO THE
FORECAST. IF THE TROUGH IS DOMINANT THE COOLER WEATHER WILL STICK
AROUND, IF NOT THEN WE CAN EXPECT A WARMING TREND THIS WEEKEND.
THE NATIONAL HURRICANE CENTER CONTINUES TO TRACK INVEST 95E IN THE
EASTERN PACIFIC. WHILE THERE IS NOW A 100% CHANCE OF TROPICAL
CYCLONE FORMATION OVER THE NEXT 48 HOURS, THE CIRCULATION CENTER
WAS DISPLACED FROM THE THUNDERSTORM ACTIVITY AND IT STRUGGLED TO
GET ORGANIZED TODAY. THE EVENTUAL TRACK OF THIS SYSTEM IS STILL
UNCERTAIN, WITH THE ENSEMBLES SHOWING A BI-MODAL SOLUTION. ONE OF
THESE OUTCOMES WOULD BRING WIND AND RAIN TO SOUTHERN CALIFORNIA
AROUND SUNDAY OR MONDAY. EITHER THE PNW CUT-OFF LOW WILL MOVE FAR
ENOUGH SOUTH TO PULL THE DECAYING TROPICAL CYCLONE TOWARDS
SOUTHERN CALIFORNIA, OR HIGH PRESSURE WILL BUILD SOUTH OF THE LOW,
FORCING THE STORM HARMLESSLY TO THE NW. WHILE THERE IS A LOT OF
HYPE AROUND DIFFERENT DETERMINISTIC SOLUTIONS, IT'S MUCH MORE
APPROPRIATE TO LOOK AT ENSEMBLES IN THIS TIME RANGE. BOTH THE GEFS
AND ECMWF ENSEMBLE SHOW A 20-30% CHANCE OF TROPICAL DEPRESSION
LEVEL IMPACTS IN SOUTHERN CALIFORNIA, AND A 10-20% CHANCE OF
TROPICAL STORM TYPE IMPACTS. EVEN IN THE WORST CASE SCENARIO, OUR
CWA WOULDN'T GET NEARLY AS MUCH RAIN OR WIND AS SOUTHERN
CALIFORNIA. THE CURRENT HIGH END SCENARIO (90TH PERCENTILE) WOULD
BRING 1/4" OF RAIN TO THE CENTRAL COAST. THE MOST LIKELY OUTCOME
IS NO SIGNIFICANT IMPACTS, AND THE ENSEMBLES HAVE TRENDED MORE IN
THAT DIRECTION OVER THE LAST 24 HOURS. THERE IS VIRTUALLY NO
CHANCE FOR HURRICANE IMPACTS IN CALIFORNIA. IT'S WORTH WATCHING IF
ANOTHER SYSTEM FORMS BEHIND 95E, AS PERSISTENT TROUGHING COULD
KEEP THE DOOR OPEN THROUGH NEXT WEEK.
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...FLYNN
LONG TERM....FLYNN
AVIATION...DIALH
MARINE...DIALH
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