383
FXUS66 KMTR 031748
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
948 AM PST MON FEB 3 2025
..NEW AVIATION, MARINE
SYNOPSIS
ISSUED AT 304 AM PST MON FEB 3 2025
A SECOND, STRONGER AR ARRIVES LATER TODAY AND CONTINUES INTO
TUESDAY. THIS SYSTEM IS EXPECTED TO BRING MUCH HIGHER RAIN TOTALS
AND A RETURN TO ELEVATED FLOOD RISK ACROSS THE BAY AREA AND
CENTRAL COAST. A FLOOD WATCH WILL GO INTO EFFECT AT 4 PM PST THIS
AFTERNOON AND WILL REMAIN IN EFFECT THROUGH 4 AM PST WEDNESDAY.
WET WEATHER WILL CONTINUE THROUGH THE REMAINDER OF THE WEEK.
UPDATE
ISSUED AT 945 AM PST MON FEB 3 2025
THE FIRST PART OF THE DAY WILL BE THE PROVERBIAL CALM BEFORE THE
STORM. THE BIG STORY FOR TODAY WILL BE THE STORM LURKING TO OUR
WEST THAT WILL ULTIMATELY IMPACT THE BAY AREA AND CENTRAL COAST
LATER TODAY AND TONIGHT. DETAILS ON THE IMPENDING STORM ARE
BELOW. UNTIL THE STORM ARRIVES WE'LL SEE A FEW SCOUT SHOWERS
TRAVERSE THE BAY AREA THIS MORNING INTO THE AFTERNOON. KMUX RADAR
IS PICKING UP ON A FEW OF THESE SHOWERS WITH A AUTOMATED SENSORS
TIPPING A FEW HUNDREDTHS. LATEST SURFACE ANALYSIS SHOWS A
STATIONARY FRONT STILL PARKED NORTH OF THE NORTH BAY (IT'S BEEN
THERE SINCE SUNDAY). FOLLOW THIS BOUNDARY WESTWARD AND YOU'LL SEE
OUR LURKING STORM. A LOW PRESSURE SYSTEM NEAR 32N 143W WILL INCH
ITS WAY TOWARD THE COAST THIS AFTERNOON/EVENING. THE EASTWARD
MOVEMENT OF THE SURFACE LOW WILL HELP TO MOVE THE STATIONARY FRONT
SOUTHWARD INTO THE NORTH BAY. AS THIS HAPPENS, RAIN WILL BEGIN TO
INCREASE ACROSS THE NORTH BAY WITH IMPACTS FOR THE EVENING
COMMUTE. IN ADDITION TO THE ONSET OF PRECIP, THE DROPPING BOUNDARY
AND TIGHTENING SURFACE PRESSURE GRADIENT WILL RESULT IN THE FIRST
UPTICK IN WINDS. WINDS WILL RAPIDLY INCREASE OVER THE COASTAL
WATERS AND NORTH BAY COAST THIS AFTERNOON/EVENING.HI-RES MODELS
ARE INDICATING A ROBUST 925-850MB JET TAKING AIM INITIALLY OVER
THE NORTH BAY COAST BEFORE SLIDING SOUTHWARD THROUGH TUESDAY. AS
SUCH A TWO WIND ADVISORIES HAVE BEEN ISSUED FOR COASTAL AREAS.
FIRST ONE BEGINS THIS AFTERNOON NORTH OF MONTEREY BAY AND THE
SECOND ONE GOLDEN GATE SOUTHWARD FOR TUESDAY.
MORAL OF THE MORNING UPDATE, IF YOU NEED TO PREP FOR THE INCOMING
STORM DO IT NOW. RAIN AND GUSTY WINDS ARE ON THE WAY. DOUBLE CHECK
THE GUTTERS, STORM DRAINAGES, WEAKENED BRANCHES, ETC.
MM
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 304 AM PST MON FEB 3 2025
KEY POINTS:
* FLOOD ADVISORY CONTINUES FOR PORTIONS OF SONOMA COUNTY INTO MONDAY
* FLOOD WATCH GOES INTO EFFECT 4 PM MONDAY THROUGH 4 AM WEDNESDAY
ACROSS THE BAY AREA AND CENTRAL COAST
* SECOND AR ARRIVES LATE MONDAY BRINGING MODERATE TO AT TIMES HEAVY
RAIN
* THIRD AR ARRIVES THURSDAY-FRIDAY BUT IS EXPECTED TO BE WEAKER AND
AIMED FARTHER SOUTH
* COLD MORNING TEMPERATURES RETURN MID-WEEK BUT TEMPERATURES
WILL DROP MORE SIGNIFICANTLY OVER THE WEEKEND
LIGHT SHOWERS CONTINUE TO THE NORTH OF OUR CWA BUT ARE EXPECTED TO
SHIFT SOUTHWARDS AGAIN AS A SECOND, STRONGER, AR ARRIVES LATER
TODAY. FORECAST IVT VALUES ARE IN EXCESS OF 600 TO 700 KG/MS WHICH
IS SUPPORTIVE OF A MORE MODERATE INTENSITY AR ARRIVING MID TO LATE
MONDAY AND CONTINUING INTO TUESDAY. THE FIRST ROUND OF MODERATE TO
HEAVY RAIN WILL TAKE PLACE LATER IN THE DAY ON MONDAY AND A SECOND
ROUND OF HEAVIER RAIN WILL TAKE PLACE ON TUESDAY. WHILE THE BULK OF
THE MOISTURE IS STILL LOCATED TO OUR NORTH, THERE WILL BE ENOUGH
LINGERING MOISTURE FOR LIGHT SHOWERS ACROSS THE REGION MONDAY
MORNING. BY THE LATE MORNING/EARLY AFTERNOON, SHOWERS WILL START TO
PICK UP IN INTENSITY ACROSS THE NORTH BAY AS TROUGHING DEEPENS OVER
THE PACIFIC AND A SHORTWAVE APPROACHES THE WEST COAST. THIS
SHORTWAVE, IN COMBINATION WITH THE SUB-TROPICAL JET LIFTING
NORTHWARD, WILL PUSH THE MAIN MOISTURE PLUME SOUTHWARDS WITH SHOWER
ACTIVITY SUBSEQUENTLY INCREASING THROUGHOUT THE DAY ACROSS THE BAY
AREA AND CENTRAL COAST. AT THE SAME TIME, A STATIONARY COLD FRONT
OVER NORTHERN CA WILL GRADUALLY GIVE WAY TO A MORE PROGRESSIVE COLD
FRONT AS A SURFACE LOW ASSOCIATED WITH THIS SHORTWAVE MOVES INLAND.
THE INITIAL RAIN (ON MONDAY) WILL PRIMARILY BE CONCENTRATED OVER THE
NORTH BAY THROUGH THE LATE AFTERNOON BEFORE WE START TO SEE MORE
MODERATE INTENSITY RAIN SHIFT SOUTH OF THE BAY BRIDGE OVER THE
EVENING HOURS. RAINFALL TOTALS - FOR MONDAY - WILL BE HIGHEST ACROSS
THE NORTH BAY MOUNTAINS WHICH WILL SEE BETWEEN 1.5"-2". ELSEWHERE,
INITIAL RAIN TOTALS OF UP TO AN 1" ARE POSSIBLE ON MONDAY WITH THE
BULK OF THE RAIN FROM THIS AR TO FALL LATE MONDAY INTO TUESDAY. AS
THIS OCCURS, WE WILL SEE A SOUTHWARDS SHIFT IN WHERE THE HIGHEST
RAINFALL TOTALS ARE LOCATED WITH AN EMPHASIS ON THE SANTA CRUZ
MOUNTAINS AND SANTA LUCIA RANGE (SEE THE LONG TERM DISCUSSION FOR
MORE INFORMATION). GUSTY WINDS RAMP UP ALONG THE COAST AND ACROSS
ELEVATED TERRAIN MONDAY INTO TUESDAY. WHILE WINDS GENERALLY STAY
BELOW WIND ADVISORY CRITERIA, COASTAL AREAS MAY FLIRT WITH WIND
ADVISORY CRITERIA MONDAY AFTERNOON/EVENING AROUND THE TIME OF
FRONTAL PASSAGE. FOR NOW, CONTINUING TO HOLD OFF ON A WIND ADVISORY
DUE TO THE SHORT DURATION AND MORE ISOLATED NATURE OF HIGHER GUSTS
BUT WILL CONTINUE TO MONITOR AND UPDATE IF THINGS CHANGE.
THE WPC HAS ISSUED A DAY ONE (MONDAY) SLIGHT RISK (15%) OF EXCESSIVE
RAINFALL FOR THE NORTH BAY AND A MARGINAL RISK (5%) FOR PORTIONS OF
THE BAY AREA AND CENTRAL COAST. A FLOOD WATCH WILL GO INTO EFFECT AT
4 PM PST ON MONDAY FOR THE BAY AREA AND CENTRAL COAST AS RAIN STARTS
TO RAMP UP IN INTENSITY AND BECOMES MORE WIDESPREAD ACROSS THE
REGION. AS HAS BEEN TALKED ABOUT FOR THE PAST FEW DAYS, RAINFALL
ACROSS THE NORTH BAY AND COASTAL AREAS HAS ACTED TO SATURATE SOILS
AND HAS ESSENTIALLY "PRIMED" THEM FOR FLOODING TO OCCUR. FOR AREAS
THAT HAVE NOT RECEIVED AS MUCH RAIN, MODERATE TO HEAVY RAIN IS
EXPECTED TO SATURATE SOILS FAIRLY QUICKLY MONDAY/TUESDAY WITH
INCREASED POTENTIAL FOR URBAN NUISANCE FLOODING AS HEAVIER RAIN
RATES OCCUR. WHILE THE MOST RECENT CNRFC FORECASTS CONTINUE TO LIMIT
MAINSTREAM RIVER FLOODING TO THE NORTH BAY, SMALLER CREEKS AND
STREAMS ACROSS THE REST OF THE BAY AREA AND CENTRAL COAST MAY SEE
SHARP RISES AS THE BULK OF THE RAIN PASSES THROUGH. IF YOU ENCOUNTER
A FLOODED ROADWAY OR ROAD CLOSURE BARRICADES REMEMBER - TURN AROUND,
DON'T DROWN!
LONG TERM
(TUESDAY THROUGH SUNDAY)
ISSUED AT 304 AM PST MON FEB 3 2025
HEADING INTO TUESDAY, HEAVIER SHOWERS WILL SPREAD INTO THE REST OF
THE BAY AREA AND CENTRAL COAST OVERNIGHT WITH THE HIGHEST
ACCUMULATIONS ANTICIPATED IN THE SANTA CRUZ MOUNTAINS AND SANTA
LUCIA RANGE. RAIN MAY BRIEFLY LIGHTEN MID TO LATE MORNING BUT
WIDESPREAD HEAVY RAIN WILL RETURN TUESDAY AFTERNOON AS A SECOND
PULSE OF MOISTURE (HIGHER IVT VALUES IN EXCEEDANCE OF 700 KG/MS)
ARRIVES. THIS SECOND PULSE WILL BE ASSOCIATED WITH WITH THE GREATEST
FLOOD RISK AS ANY AREAS NOT PREVIOUSLY SATURATED BY THE FRIDAY TO
SUNDAY RAINS WILL BE AT LEAST PARTIALLY SATURATED FROM THE MONDAY TO
EARLY TUESDAY MORNING RAINS. MODERATE TO HEAVY RAINS WILL THEN
PERSIST THROUGH THE EVENING HOURS BEFORE RAINS DECREASE IN INTENSITY
OVERNIGHT TUESDAY INTO WEDNESDAY. WHEN ALL IS SAID AND DONE FROM
MONDAY TO TUESDAY, THE NORTH BAY WILL (IN TOTAL) SEE AN ADDITIONAL
2"-4", AN ADDITIONAL 1"-3" SOUTH OF THE BAY BRIDGE, 3"-5" IN THE
SANTA CRUZ MOUNTAINS, 1"-2" ACROSS THE CENTRAL COAST, AND 5"-8"+ IN
THE SANTA LUCIA RANGE. GIVEN THAT THE MOISTURE PLUME IS ORIENTED
ALMOST PERPENDICULAR TO THE COASTLINE, AREAS WHERE OROGRAPHIC UPLIFT
IS FAVORED MAY SEE LOCALLY HIGHER TOTALS THAN PREVIOUSLY MENTIONED.
AN ADDITIONAL FACTOR IS THAT OVER THE LAST FEW GRID UPDATES THE
FORECASTED QPF TOTALS HAVE CONTINUED TO INCREASE FOR THIS EVENT WITH
PARTICULAR EMPHASIS ON THE SOUTHERN PORTIONS OF OUR CWA (SANTA CRUZ,
MONTEREY, AND SAN BENITO COUNTIES). AS SUCH, IT IS IMPORTANT TO STAY
UP TO DATE ON THE MOST RECENT FORECAST AND BE AWARE THAT THERE IS
ELEVATED POTENTIAL FOR FLOODING TO OCCUR. THE WPC HAS ISSUED A
WIDESPREAD DAY TWO (TUESDAY) SLIGHT RISK (15%) OF EXCESSIVE RAINFALL
EXCEEDING FLASH FLOOD GUIDANCE ACROSS THE BAY AREA AND COASTAL
CENTRAL COAST AND A MARGINAL RISK (5%) OF EXCEEDING FLASH FLOOD
GUIDANCE ACROSS INTERIOR MONTEREY/SAN BENITO COUNTIES. GUSTY WINDS
WILL CONTINUE THROUGH THE DAY ON TUESDAY BEFORE WEAKENING TUESDAY
NIGHT INTO WEDNESDAY. WINDS CONTINUE TO LOOK BELOW WIND ADVISORY
CRITERIA ON TUESDAY BUT WE WILL CONTINUE TO MONITOR IN CASE FRONTAL
PASSAGE SLOWS DOWN AND THE TIME PERIOD OF STRONGER WINDS BECOMES
MORE PROLONGED.
WEDNESDAY WILL BE THE LULL BETWEEN OUR MONDAY-TUESDAY AR AND OUR
THURSDAY-FRIDAY AR. LINGERING MOISTURE MAY BE ENOUGH TO SUPPORT
SCATTERED, LIGHT SHOWERS BUT ANY TOTALS FROM THIS WILL GENERALLY BE
BELOW A TENTH OF AN INCH. NOTABLY, MORNING TEMPERATURES WILL BEGIN
TO DROP WEDNESDAY AFTER COLD FRONTAL PASSAGE OCCURS MONDAY/TUESDAY.
THIS MAY NECESSITATE THE ISSUANCE OF FROST/FREEZE PRODUCTS FOR
PORTIONS OF THE BAY AREA AND CENTRAL COAST.
THURSDAY TO FRIDAY WILL SEE A THIRD, ALBEIT WEAKER, AR IMPACTING OUR
CWA WITH ADDITIONAL TOTALS BETWEEN 1"-2" LIKELY ACROSS THE REGION.
THIS SYSTEM WILL BE SPURRED BY THE ARRIVAL OF ANOTHER UPPER LEVEL
SHORTWAVE AND A SURFACE LOW PRESSURE SYSTEM WITH IVT GUIDANCE
SHOWING A SUBTROPICAL MOISTURE TAP. THE MAIN THING TO NOTE ABOUT
THIS SYSTEM IS THAT, SO FAR, IT LOOKS FAIRLY PROGRESSIVE AND HAS
STARTED TO TREND MORE SOUTHWARDS (CENTRAL COAST INTO SOUTHERN CA) ON
RECENT MODEL RUNS. THIS MAY RESULT IN ADDITIONAL FLUCTUATIONS IN
FORECASTED QPF AMOUNTS THURSDAY AND FRIDAY AS WE GET CLOSER TO THIS
AR. ANOTHER COLD FRONT IS EXPECTED TO PASS THROUGH THE REGION ON
FRIDAY BRINGING WITH IT LOCALLY GUSTY WINDS AND A MORE SIGNIFICANT
DROP IN MORNING TEMPERATURES ON SATURDAY/SUNDAY. CURRENT GUIDANCE
SUGGESTS TEMPERATURES MAY DROP INTO THE 30S TO UPPER 20S. THE
COMBINATION OF PROLONGED WET CONDITIONS, GUSTY WINDS, AND COOLER
TEMPERATURES WILL CREATE HAZARDOUS CONDITIONS FOR ANYONE WITHOUT
ACCESS TO ADEQUATE HEATING OR SHELTER. THE ISSUANCE OF ADDITIONAL
FROST AND FREEZE PRODUCTS ARE LIKELY SATURDAY AND SUNDAY.
AVIATION
(18Z TAFS)
ISSUED AT 947 AM PST MON FEB 3 2025
MAINLY VFR CONDITIONS ATTM EXCEPT FOR KSTS, WHERE IFR TO MVFR IS
EXPECTED TO PERSIST THROUGH THE AFTERNOON, WHEN CIGS WILL HOVER
BETWEEN VFR/MVFR THIS EVENING WITH PERIODS OF MODERATE TO HEAVY
RAINFALL AND STRONG SOUTHERLY WINDS OUT AHEAD OF A STRENGTHENING
SURFACE COLD FRONT. EXPECT ISSUES WITH LLWS LATE TONIGHT THROUGH
EARLY TUESDAY MORNING AS WELL.
VICINITY OF SFO...VFR IS EXPECTED TO PREVAIL THROUGH LATE AFTERNOON
INTO THE EARLY EVENING HOURS WHEN CIGS ARE EXPECTED TO DROP INTO
MVFR WITH REDUCED VISIBILITY DURING TIMES OF MODERATE TO HEAVY
RAINFALL THROUGH THE OVERNIGHT. ALONG WITH THE RAINFALL AND MVFR
CIGS EXPECT STRONG SOUTHERLY COMPONENT WINDS OUT AHEAD OF A
STRENGTHENING SURFACE COLD FRONT. AN AIRPORT WEATHER WARNING FOR
STRONG WINDS IS IN EFFECT UNTIL LATE EARLY TUESDAY, AT 3AM PST.
ALTHOUGH NOT CURRENTLY IN THE TAF, BE AWARE THERE IS A CHANCE FOR
LLWS.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR IS EXPECTED TO PREVAIL THROUGH THE
REMAINDER OF TODAY AND TONIGHT WITH MVFR CEILINGS DEVELOPING
OVERNIGHT. DRAINAGE WINDS THROUGH KSNS ARE EXPECTED TO INCREASE OVER
NIGHT INTO TUESDAY OUT AHEAD OF AN ADVANCING SURFACE COLD FRONT.
MARINE
(TODAY THROUGH SATURDAY)
ISSUED AT 947 AM PST MON FEB 3 2025
A COLD FRONT WILL BEGIN TO GRADUALLY MOVE SOUTH THROUGH THE DAY
INTO TUESDAY, AS THE GRADIENT STRENGTHENS WE'LL SEE SOUTH AND
SOUTHWEST WINDS INCREASE OUT AHEAD OF THE FRONT. GALE STRENGTH
WINDS WILL BEGIN TO DEVELOP OVER THE NORTHERN WATERS THIS
AFTERNOON WITH THE GALE STRENGTH WIND FIELD INCREASING OUT AHEAD
OF THE FRONT TO OUR SOUTHERN COASTAL WATERS TONIGHT INTO TUESDAY.
EXPECT PERIODS OF MODERATE TO HEAVY RAINFALL TO ACCOMPANY THE
STRONG WINDS. EXPECT MODERATE SIGNIFICANT WAVE HEIGHTS WITH FRESH
SWELLS AND STEEP WIND WAVES RESULTING IN HAZARDOUS MARINE
CONDITIONS. ANOTHER DISTURBANCE WILL IMPACT OUR COASTAL WATERS
LATER THIS WEEK BEGINNING THURSDAY, AND PERSISTING INTO FRIDAY.
HYDROLOGY
ISSUED AT 803 PM PST SUN FEB 2 2025
DETERMINISTIC FORECASTS KEEP MAIN STEM RIVERS BELOW FLOOD STAGE;
HOWEVER, THE EXCEEDANCE PROBABILITIES (OF RISING ABOVE FLOOD STAGE)
FOR REACHING FLOOD THRESHOLDS ARE NON-ZERO FOR THE FOLLOWING
MAIN STEM FORECAST POINTS: GUEC1 - RUSSIAN RIVER AT GUERNEVILLE
HAS A 36% PROBABILITY OF EXCEEDING ACTION/MONITOR STAGE AND A 25%
PROBABILITY OF EXCEEDING MINOR FLOOD STAGE, HEAC1 - RUSSIAN RIVER
NEAR HEALDSBURG HAS A 5% PROBABILITY OF EXCEEDING ACTION/MONITOR
STAGE, APCC1 - NAPA RIVER NEAR NAPA HAS A 27% PROBABILITY OF
EXCEEDING ACTION/MONITOR STAGE AND A 20% PROBABILITY OF EXCEEDING
MINOR FLOOD STAGE, SHEC1 - NAPA RIVER NEAR SAINT HELENA HAS A 32%
PROBABILITY OF EXCEEDING ACTION/MONITOR STAGE AND AN 18%
PROBABILITY OF EXCEEDING MINOR FLOOD STAGE, BTEC1 - SAN LORENZO
RIVER AT BIG TREES HAS AN 11% PROBABILITY OF EXCEEDING
ACTION/MONITOR STAGE AND A LESS THAN 2% PROBABILITY OF EXCEEDING
MINOR FLOOD STAGE. DETERMINISTIC FORECASTS FOR THE NON-MAIN STEM
FORECAST POINTS OF CTIC1 - LAGUNA DE SANTA ROSA AT STONY POINT
ROAD NEAR COTATI AND MWEC1 - MARK WEST CREEK AT MIRABEL HEIGHTS
REACH MINOR FLOOD STAGE BETWEEN NOW AND FRIDAY.
SARMENT
MTR WATCHES/WARNINGS/ADVISORIES
CA...WIND ADVISORY FROM 3 PM THIS AFTERNOON TO 1 AM PST TUESDAY FOR
CAZ006-502-505-509.
FLOOD WATCH FROM 4 PM PST THIS AFTERNOON THROUGH LATE TUESDAY
NIGHT FOR CAZ006-502>506-508>510-512>518-528>530.
WIND ADVISORY FROM 7 AM TO 8 PM PST TUESDAY FOR CAZ509-512-517-
529-530.
PZ...SMALL CRAFT ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR MRY BAY-
PIGEON PT TO PT PINOS 0-10 NM-PIGEON PT TO PT PINOS 10-60
NM-PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM-SF BAY N OF BAY
BRIDGE.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 3 AM PST TUESDAY FOR SF
BAY N OF BAY BRIDGE.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 9 PM PST TUESDAY FOR
MRY BAY-PIGEON PT TO PT PINOS 10-60 NM-PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM.
GALE WARNING UNTIL 9 PM PST THIS EVENING FOR PT ARENA TO PT
REYES 0-10 NM.
GALE WARNING UNTIL 9 AM PST TUESDAY FOR PT REYES TO PIGEON PT 0-
10 NM.
GALE WARNING FROM 3 PM THIS AFTERNOON TO 9 AM PST TUESDAY FOR
PIGEON PT TO PT PINOS 0-10 NM.
GALE WARNING UNTIL 9 PM PST TUESDAY FOR PT ARENA TO PT REYES 10-
60 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...JM
MARINE...JM
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