483
FXUS66 KMTR 221611
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
911 AM PDT WED OCT 22 2025
..NEW UPDATE
KEY MESSAGES
UPDATED AT 1241 AM PDT WED OCT 22 2025
- SLIGHT CHANCE FOR ISOLATED SHOWERS AND THUNDERSTORMS THIS
MORNING.
- RAIN CHANCES RETURN LATE FRIDAY AND CONTINUE THROUGH THE
WEEKEND.
- LARGE SWELL WILL CONTINUE TO BRING HAZARDOUS BEACH CONDITIONS
THROUGH THE WEEKEND.
UPDATE
ISSUED AT 854 AM PDT WED OCT 22 2025
PRETTY ACTIVE START TO THE DAY ACROSS THE CENTRAL COAST THANKS TO
A NEARBY UPPER LOW (LIFT), INSTABILITY, AND SOME MOISTURE. SHOWERS
AND THUNDERSTORMS DID DEVELOP AND FILLED IN OVER MONTEREY AND SAN
BENITO CONTINUES. RAINFALL AMOUNTS OVER THE LAST 12 HOURS HAVE
GENERALLY BE A FEW HUNDREDTHS AND UP TO A 0.10" UNDER THE WETTEST
CELLS. AS FOR LIGHTNING, ROUGHLY 550 STRIKES ACROSS THE REGION
WITH A HANDFUL STRIKING THE GROUND WITH LITTLE RAINFALL.
NORMALLY, THIS WOULD BE PROBLEMATIC BUT RAINS FROM EARLIER IN OCT
HAVE LIMITED FIRE WEATHER CONCERNS. HAVE NOT SEEN OR HEARD OF ANY
NEW FIRE IGNITIONS. THAT BEING SAID, LOCAL FIRE PARTNERS WILL
LIKELY BE CHECKING OVER THE NEXT DAY FOR IGNITIONS.
FOR THE REST OF THE MORNING AND INTO THE AFTERNOON, DID A QUICK
UPDATE TO THE FORECAST TO BETTER REFLECT REALITY WITH CURRENT
SHOWERS/TSTORMS. THERE HAS BEEN A DOWNWARD TREND WITH ACTIVITY AS
IT HAS TRACKED OUT OF THE CENTRAL COAST AND INTO SANTA CRUZ/SANTA
CLARA/EAST BAY REGION. BEST CHC FOR THUNDERSTORMS WILL CONTINUE
THROUGH ABOUT 18Z BEFORE DIMINISHING. THERE IS STILL A CHANCE FOR
A FEW POPCORN SHOWERS BROADER BAY AREA THIS AFTERNOON AS MOISTURE
WRAPS AROUND THE UPPER LOW AS IT DEPARTS EASTWARD.
MM
SHORT TERM
ISSUED AT 1241 AM PDT WED OCT 22 2025
(TODAY AND TONIGHT)
AN UPPER LEVEL LOW PRESSURE SYSTEM OVER THE NE PACIFIC WILL MOVE
OVER THE CENTRAL COAST THROUGH THE MORNING. THIS WILL BRING A
SLIGHT CHANCE FOR HIGH BASED SHOWERS, WITH A FEW THUNDERSTORMS
POSSIBLE THROUGH MIDDAY. THE BEST CHANCE IS ACROSS THE INTERIOR
CENTRAL COAST, BUT THERE IS STILL A 10-15% CHANCE ACROSS PORTIONS
OF THE BAY AREA SOUTH OF THE BAY BRIDGE. HIGH RESOLUTION MODEL
SOUNDINGS SHOW THE INSTABILITY IS STRICTLY IN THE MID TO UPPER
TROPOSPHERE. THE HRRR SOUNDING FOR HOLLISTER AT 3 AM SPECIFICALLY
SHOWS 700-500MB LAPSE RATE OF 8.1 C/KM, BUT A STABLE MARINE LAYER
INVERSION PERSISTING AT THE SURFACE. THE PW SHOULD PEAK AROUND 1"
WITH A NOTICEABLE DRY LAYER BETWEEN 900 AND 700 MB. THIS DRY
LAYER WILL CAUSE MOST OF THE RAIN PRODUCED FROM THE HIGH BASED
SHOWERS TO EVAPORATE BEFORE REACHING THE GROUND. A FEW LIGHTNING
STRIKES ARE POSSIBLE, PARTICULARLY IN THE FEW HOURS SURROUNDING
SUNRISE. WE HAVEN'T SEEN ANY THUNDERSTORMS IN OUR AREA YET, BUT
THERE ARE A FEW ONGOING IN THE SAN JOAQUIN VALLEY. WE'RE GETTING
SOME RETURNS ON RADAR, BUT NO REPORTS OF ANY MEASURABLE RAIN
HITTING THE GROUND.
OTHERWISE THE INCREASED CLOUD COVER AND DECREASING THICKNESS WILL
BRING COOLER TEMPERATURES TODAY. THE COAST WILL BE AROUND 5
DEGREES COOLER THAN YESTERDAY. IN OTHER WORDS, MOST AREAS WILL BE
STUCK IN THE 60S TODAY. THE SKIES WILL TAKE A WHILE TO CLEAR, BUT
THE SUN MAY START TO PEAK OUT IN THE LATE AFTERNOON FOR SOME AS
THE LOW MOVES INLAND AND DRIER, MORE STABLE AIR MOVES IN.
LONG TERM
ISSUED AT 1241 AM PDT WED OCT 22 2025
(THURSDAY THROUGH TUESDAY)
A QUICKLY BUILDING SHORT WAVE RIDGE WILL REPLACE THE CUT-OFF LOW
BY THURSDAY MORNING. THIS WILL CAUSE THE MARINE LAYER TO COMPRESS,
AND TEMPERATURES WILL RETURN TO NORMAL FOR THURSDAY - FRIDAY.
AFTER THIS BRIEF RESPITE, THE ATMOSPHERE WILL BECOME UNSETTLED
AGAIN BY FRIDAY NIGHT OR SATURDAY MORNING BRINGING COOL, WET
CONDITIONS THROUGH THE WEEKEND. INSTEAD OF A CUT-OFF LOW FROM THE
SOUTH, THIS NEXT SYSTEM WILL BE DRIVEN BY A DIP IN THE JET STREAM
AND ASSOCIATED COLD FRONT AT THE SURFACE. SW FLOW AHEAD OF THE
FRONT WILL PUMP TROPICAL MOISTURE TO THE BAY AREA, WITH PW PEAKING
AROUND 1.2-1.5" SATURDAY MORNING. THIS MOISTURE PLUME WILL SLIDE
SOUTH THROUGH THE DAY, REACHING SOUTHERN CALIFORNIA BY SATURDAY
NIGHT. THE PRECIPITATION MODE WILL LIKELY CHANGE FROM STRATIFORM
TO CONVECTIVE IN THE COLD AIR MASS BEHIND THE FRONT. OUR CURRENT
FORECAST HAS THE RAIN TAPERING OFF MONDAY MORNING, ALTHOUGH THERE
IS SOME INDICATION IT MAY LAST INTO TUESDAY. EITHER WAY THE RAIN
TOTALS CONTINUE TO DECREASE WITH NOW AROUND 1/2 INCH EXPECTED IN
THE NORTH BAY AN CLOSER TO 1/10TH ACROSS THE BAY AREA. IT LOOKS
LIKE THE CENTRAL COAST WILL ONLY GET A FEW HUNDREDTHS, OUTSIDE OF
THE SANTA CRUZ MOUNTAINS. NO MAJOR FLOODING IMPACTS ARE EXPECTED
AND THIS LOOKS TO BE BENEFICIAL RAINFALL.
AVIATION
(12Z TAFS)
ISSUED AT 356 AM PDT WED OCT 22 2025
MORE DIFFICULT MIXED SKIES FORECAST TODAY AS MOISTURE ALOFT SITS
ABOVE OUR MARINE LAYER. SOME DISRUPTIONS IN THE LOWER-LEVEL CLOUD
DECKS CAN BE ANTICIPATED THRU SUNRISE THIS MORNING. THEREFORE,
CIGS HEIGHT IN TAFS IS GENERALLY LOWER CONFIDENCE, WHILE TIMING
CONFIDENCE IS MODERATE. ONGOING SHOWER AND THUNDERSTORM ACTIVITY
WILL LARGELY BE CONFINED TO AREAS SOUTH OF KSFO/KOAK.
VICINITY OF SFO...VERY LOW BUT NON-ZERO CHANCE OF AN ISOLATED
SHOWER OR TWO INVOF THE TERMINAL THRU SUNRISE THIS MORNING. ONCE
AGAIN, MODERATE CONFIDENCE IN TIMING WITH A BIT LESS CONFIDENCE IN
CIGS HEIGHT, AS THE ATMOSPHERE WILL BE MIXED UP DUE TO ONGOING
CONVECTION SOUTH OF THE BAY.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...ONGOING SHOWERS AND THUNDERSTORMS
CONTINUE THROUGH SUNRISE THIS MORNING. MODERATE CONFIDENCE IN
PATCHY DENSE FOG AROUND THE MONTEREY BAY REGION BY THE OVERNIGHT
HOURS TONIGHT GOING INTO THURSDAY MORNING.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 356 AM PDT WED OCT 22 2025
A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS THE SOUTHERN
WATERS THIS MORNING. GENTLE TO MODERATE BREEZE PERSISTS THROUGH
TODAY. ISOLATED GUSTY CONDITIONS MAY EXIST AROUND SHOWERS AND
THUNDERSTORMS THIS MORNING. SEAS ABATE INTO THURSDAY BEFORE
BUILDING AGAIN FRIDAY THROUGH THIS WEEKEND.
BEACHES
ISSUED AT 252 PM PDT TUE OCT 21 2025
A LONG PERIOD NORTHWESTERLY SWELL WILL CONTINUE TO BRING AN
INCREASED RISK FOR SNEAKER WAVES AND RIP CURRENTS THROUGH WEDNESDAY.
ADDITIONALLY, BREAKING WAVES OF 12-17 FEET AND LOCALLY AS HIGH AS 25
FEET WILL BE POSSIBLE. SNEAKER WAVES CAN UNEXPECTEDLY RUN
SIGNIFICANTLY FARTHER UP THE BEACH THAN NORMAL, INCLUDING OVER ROCKS
AND JETTIES. RIP CURRENTS ARE TYPICALLY MORE FREQUENT AND STRONGER
IN THE VICINITY OF JETTIES, INLETS, AND PIERS. SWIMMERS SHOULD
ALWAYS SWIM NEAR A LIFEGUARD. REMAIN OUT OF THE WATER TO AVOID
HAZARDOUS SWIMMING CONDITIONS AND NEVER TURN YOUR BACK ON THE OCEAN!
SARMENT
MTR WATCHES/WARNINGS/ADVISORIES
CA...BEACH HAZARDS STATEMENT THROUGH LATE TONIGHT FOR CAZ006-505-509-
529-530.
PZ...SMALL CRAFT ADVISORY UNTIL 9 PM PDT THIS EVENING FOR PIGEON PT
TO PT PINOS 10-60 NM-PT ARENA TO PT REYES 10-60 NM.
SHORT TERM...FLYNN
LONG TERM....FLYNN
AVIATION...BEHRINGER
MARINE...BEHRINGER
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