749
FXUS66 KMTR 200020
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
420 PM PST FRI DEC 19 2025
..NEW SHORT TERM, LONG TERM
KEY MESSAGES
UPDATED AT 315 AM PST FRI DEC 19 2025
- LIGHT TO MODERATE RAIN TONIGHT AND SATURDAY FOR THE NORTH BAY,
BAY AREA AND EAST BAY
- FOCUS OF MODERATE RAINFALL SHIFTS SOUTH INTO BAY AREA TO SANTA
CRUZ MOUNTAINS ON SUNDAY WITH A SLIGHT CHANCE OF THUNDERSTORMS
- RAIN CHANCES PERSIST ON MONDAY, BUT MONDAY APPEARS TO BE THE
LEAST IMPACTFUL DAY IN THE EXTENDED FORECAST
- TUESDAY THROUGH FRIDAY WILL BRING STRONG WINDS AND PERIODS OF
HEAVY RAINFALL FOR MUCH OF OUR AREA, EXPECT EXTENSIVE TRAVEL
DELAYS
- BY THE MIDDLE OF THE WEEK INTO NEXT WEEKEND, OUR COASTAL
BEACHES AND COASTAL WATERS WILL BE EXCEPTIONALLY DANGEROUS
WHETHER YOU'RE FROM HERE OR VISITING FRIENDS AND FAMILY, STAY
AWAY
SHORT TERM
ISSUED AT 406 PM PST FRI DEC 19 2025
(THIS EVENING THROUGH SUNDAY)
LIGHT RAIN HAS BEEN ONGOING ACROSS THE NORTH BAY SINCE EARLIER THIS
MORNING WITH SOME OF THE HIGHER ELEVATION AREAS ALREADY SEEING AN
INCH OF RAIN, AND LOWER LYING AREAS SEEING MOSTLY BETWEEN 0.25"-
0.50" AS OF LATE AFTERNOON TODAY, WHICH IS A LITTLE AHEAD OF CURRENT
GUIDANCE. HIRES GUIDANCE INDICATES THE MOISTURE PLUME WILL GRADUALLY
SHIFT SOUTH TOWARD THE BAY AREA TONIGHT WITH MOSTLY LIGHT SCATTERED
RAIN, ALSO EXTENDING INTO THE EAST BAY. BY DAY BREAK SATURDAY, LIGHT
SCATTERED RAIN, OFF-AND-ON IN NATURE WILL PERSIST THROUGH THE
MORNING HOURS OVER THE SAME AREA. MUCH OF THE CENTRAL COAST WILL
RAMIN DRY SATURDAY WITH THE EXCEPTION OF THE COASTAL RANGES. THE
NEXT WAVE OF RAINFALL FROM THE ATMOSPHERIC RIVER ARRIVES ONCE AGAIN
ALONG THE COAST OF THE NORTH BAY AND BAY AREA LATE SATURDAY
AFTERNOON UNDER EMBEDDED MID-LEVEL SHORTWAVES AND SURFACE
CONVERGENCE FROM A QUASI-STATIONARY FRONT DRAPED ACROSS THE NORTH
BAY. WHILE THAT WAVE OF PRECIP MOVES OVER THE NORTHERN HALF OF OUR
FORECAST AREA SATURDAY NIGHT INTO EARLY SUNDAY, A DEVELOPING BUT
PROGRESSIVE TROUGH BEGINS TO DEEPEN TO OUR NORTH, PUSHING ONSHORE
INTO NORCAL AND OREGON BY LATE SUNDAY AFTEROON.
THE LIFT ASSOCIATED WITH THE PROGRESSIVE TROUGH AXIS PUSHING ONSHORE
DURING THE DAY SUNDAY INTO EARLY MONDAY MORNING WILL RESULT IN MORE
WIDESPREAD RAINFALL ACROSS OUR ENTIRE AREA, WITH THE HIGHER AMOUNTS
STILL FOCUSED ON THE COASTAL RANGES FROM SONOMA SOUTH TO THE SANTA
CRUZ MOUNTAINS LOOKING AT 2-3" OVER THAT SAME TIME PERIOD. INLAND
PORTIONS OF THE NORTH BAY AND BAY AREA WILL SEE APPROXIMATELY 1-2"
WITH LOCALLY HIGHER AMOUNTS FOR HIGHER ELEVATIONS INLAND BY EARLY
MONDAY MORNING. FARTHER SOUTH FOR THE SOUTH BAY AND REMAINDER OF THE
CENTRAL COAST ARE LOOKING AT BETWEEN 0.5"-1.5" OF RAIN WITH LIMITED
IMPACTS FOR THOSE AREAS. THERE IS A SLIGHT CHANCE OF EMBEDDED SUB-
SEVERE THUNDERSTORMS SUNDAY THAT MAY PRODUCE BRIEF DOWNPOURS AND
GUSTY WINDS UP TO 40MPH.
A FLOOD WATCH HAS BEEN ISSUED FOR THE NORTH BAY BEGINNING SATURDAY
AFTERNOON AT 4PM THROUGH MONDAY AFTERNOON AT 4PM. FLOOD CONCERNS ARE
RELATIVELY MINOR, CENTERED AROUND RIVERS, CREEKS AND STREAMS, THAT
MAY RISE OUT OF THEIR BANKS. LOW-LYING AREAS AND FLOOD PRONE AREAS
MAY BE IMPACTED AS WELL. REMEMBER, TURN AROUND DON'T DROWN AND NEVER
DRIVE THROUGH STANDING OR MOVING WATER.
LONG TERM
ISSUED AT 406 PM PST FRI DEC 19 2025
(SUNDAY NIGHT THROUGH NEXT FRIDAY)
BY DAY BREAK MONDAY, A DEEPER AND BROADER MIDLEVEL TROUGH FORMING TO
THE WEST OVER OPEN WATER WILL PROVIDE A PARTIAL REPRIEVE FROM
WIDESPOREAD RAINFALL AS MID-LEVEL HEIGHTS RISE DIRECTLY OVER OUR
FORECAST AREA. THE SUBTLE RISE IN MID-LEVEL HEIGHTS LOCALLY WILL
INTERUPT SOME OF THE HEAVIER RAINFALL RATES AND SHIFT THE
ATMOSPHERIC RIVER FROM THE SANTA CRUZ MOUNTAINS BACK TO THE NORTH
TOWARD THE BAY AREA AND NORTH BAY. THE BUCKLING OF THE MIDLEVEL
HEIGHT FIELDS TO THE WEST WILL REPRESENT THE BEGINNING OF THE MOST
IMPACTFUL PORTION OF THE FORECAST AS STRONG SURFACE CYCLOGENESIS
INITIATES OFFSHORE OVERNIGHT MONDAY INTO TUESDAY. BY TUESDAY
AFTERNOON A WIDE SWATH OF STRONG WINDS WILL SPREAD ACROSS OUR AREA
(ESPECIALLY OVER OUR COASTAL WATERS FROM SAN FRANCISCO SOUTH THROUGH
BIG SUR). INLAND, WINDS WILL BE GUSTY AS WELL, UP TO 40MPH AT TIMES
FOR LOW LYING AREAS AND UP TO 60MPH (OR HIGHER) ACROSS THE HIGHEST
INLAND PEAKS THROUGH EARLY WEDNESDAY MORNING. THE STRENGTHENING LOW
OFFSHORE WILL SHIFT THE FETCH OF THE ATMOSPHERIC RIVER A LITTLE
FARTHER NORTH WITH THE NORTH BAY ONCE AGAIN LOOKING TO SEE THE MOST
RAIN IN THAT TIME PERIOD, ALONG WITH THE BAY AREA, WITH LESSER
AMOUNTS TO THE SOUTH OVER THE CENTRAL COAST.
UNFORTUNATELY, A SECOND RAPIDLY DEEPNING UPPER LEVEL LOW AND ITS
ASSOCIATED TROUGH DIRECTLY ON THE HEELS OF THE AFFOREMENTIONED
STRONG SYSTEM MOVING ONSHORE TUESDAY WILL ABSORB WHATS LEFT OF THE
ATMOSPHERIC RIVER AND SLAM SEVERAL STRONG TROUGH AXIS' IN RAPID
SUCCESSION FROM THE LATTER PART OF WEDNESDAY THROUGH EARLY FRIDAY
ACROSS MOST OF THE CALIFORNIA COAST LINE. THE EXACT TIMING OF THE
STRONGEST WINDS AND HEAVIEST RAIN ARE TOO FAR OUT TO GET TOO
SPECIFIC AT THIS POINT. HOWEVER, PLAN ON EXTENSIVE TRAVEL DELAYS
WEDNESDAY THROUGH FRIDAY AND EXCEPTIONALLY DANGEROUS CONDITIONS
ALONG THE COAST LINE AND IN THE NEAR SHORE WATERS. FAMILY AND
FRIENDS VISITING THE AREA WILL ALWAYS BE CURIOUS TO BE NEAR THE
OCEAN WHILE VISTING OUR AREA. THIS WILL BE NO TIME TO CHALLENGE THE
POWER OF THE ATMOSPHERE AND THE OCEAN. WE'VE HAD NUMEROUS DEATHS
RECENTLY UP AND DOWN THE PACIFIC COAST IN OUR WATERS. NO PICTURE OR
MEMORY IS WORTH YOUR LIFE, JUST STAY AWAY FOR A MAJORITY OF THE
EXTENDED FORECAST.
AVIATION
(00Z TAFS)
ISSUED AT 346 PM PST FRI DEC 19 2025
INITIAL RAIN BAND IS MOVING OVER KSTS AND SOUTHWARD TOWARDS KOAK
AS OF 00Z. BRIEF MODERATE TO HEAVY RAIN HAS BEEN REPORTED WITH
THIS BOUNDARY AND LOWERING VSBYS AND CIGS. THE FRONT WILL MOVE
SOUTHWARD THIS EVENING BUT WEAKEN AS IT REACHES THE SOUTH BAY AND
CENTRAL COAST. LINGERING BOUNDARY LAYER MOISTURE OVERNIGHT INTO
SATURDAY MORNING WILL RESULT IN LOW CIGS AND VSBYS FROM ROUGHLY
12-18Z SATURDAY WITH SOME IMPROVEMENT THROUGH THE AFTEROON. NEXT
BOUNDARY APPROACHES LATE SATURDAY AFTERNOON WITH RAIN ARRIVING
AROUND 00Z FOR THE NORTH BAY AND GREATER BAY AREA.
VICINITY OF SFO...FRONTAL BAND PASSING OVER THE AREA FROM 00Z
THROUGH AROUND 06Z WITH PERIODS OF RAIN AND LOWERED CIGS WITH
LIGHT SOUTH WINDS. LINGERING BOUNDARY LAYER MOISTURE WILL KEEP LOW
CIGS AND REDUCED VSBYS IN PLACE THROUGH SATURDAY MORNING.
SFO BRIDGE APPROACH...SIMILAR TO SFO
MONTEREY BAY TERMINALS...VFR SKIES EARLY THIS EVENING WITH
LOWERING CIGS AFTER 03Z AS WEAK FRONTAL BOUNDARY APPROACHES WITH
SOME LIGHT PRECIP, REDUCED VSBYS AND LOWERING CIGS. MOST PRECIP
SHOULD END BY AROUND 16Z SATURDAY BUT WITH LINGERING BOUNDARY
LAYER MOISTURE.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 315 AM PST FRI DEC 19 2025
A SERIES OF STORM SYSTEMS ARRIVES TODAY AND CONTINUES THROUGH THE
EXTENDED FORECAST. MODERATE WINDS CONTINUE INTO THE WEEKEND WITH
OCCASIONAL FRESH GUSTS POSSIBLE AS A WEAK COLD FRONT MOVES THROUGH
THE COASTAL WATERS. THE FIRST SYSTEM ARRIVES FRIDAY INTO SATURDAY
WITH WIDESPREAD LIGHT RAIN EXPECTED. MODERATE TO HEAVY RAIN IS
EXPECTED BEGINNING SUNDAY AND CONTINUES THROUGH AT LEAST MID NEXT
WEEK AS TWO STRONGER SYSTEMS DEVELOP. HAZARDOUS SEAS RETURN EARLY
TO MID NEXT WEEK AS STRONG WINDS DEVELOP OVER THE COASTAL WATERS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...FLOOD WATCH FROM SATURDAY AFTERNOON THROUGH MONDAY AFTERNOON FOR
CAZ502>506.
PZ...NONE.
SHORT TERM...JM
LONG TERM....JM
AVIATION...RW
MARINE...RW
VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO
FOLLOW US ON FACEBOOK, X, AND YOUTUBE AT:
WWW.FACEBOOK.COM/NWSBAYAREA
X.COM/NWSBAYAREA
WWW.YOUTUBE.COM/NWSBAYAREA
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page