076
FXUS66 KMTR 032241
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
241 PM PST MON FEB 3 2025
..NEW SHORT TERM, LONG TERM
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.
SHORT TERM
ISSUED AT 1247 PM PST MON FEB 3 2025
(THIS EVENING THROUGH TUESDAY)
KEY POINTS:
* FLOOD ADVISORY CONTINUES FOR PORTIONS OF SONOMA COUNTY
* FLOOD WATCH GOES INTO EFFECT 4 PM MONDAY THROUGH 4 AM WEDNESDAY
ACROSS THE BAY AREA AND CENTRAL COAST
* MON PM-TUE AR ONTRACK LATE MONDAY WITH MODERATE TO AT TIMES
HEAVY RAIN
* MON PM-TUE WILL ALSO BRING GUSTY WINDS AND THUNDERSTORMS
* THUR-FRI AR IS EXPECTED TO BE WEAKER AND AIMED FARTHER SOUTH
* COLD MORNING TEMPERATURES RETURN MID-WEEK BUT TEMPERATURES
WILL DROP MORE SIGNIFICANTLY OVER THE WEEKEND
BEING UPFRONT - LENGTHY AFD AS LOTS OF INTERESTING AND IMPACTFUL
WEATHER HEADED OUR WAY.
NEAR TERM - KMUX IS SHOWING AN INCREASE IN SHOWER ACTIVITY OFF THE
NORTH BAY COAST AND NORTHERN SONOMA COUNTY. THE INCREASE IS A
RESULT OF BETTER FORCING TIED TO A LOW PRESSURE OFF THE COAST
MOVING EASTWARD. THE APPROACHING LOW HAS ALSO ALLOWED FOR GUSTY
SOUTHERLY WINDS ACROSS THE REGION THIS AFTERNOON. THIS IS ONLY A
PREVIEW OF THINGS TO COME OVER THE NEXT 36 HRS.
THIS EVENING THROUGH TUESDAY:
THE BROADER METEOROLOGICAL PICTURE STILL SHOWS A QUASI-STATIONARY
BOUNDARY TO THE NORTH. THIS FRONT EXTENDS WEST TO A SURFACE LOW
NEAR A TRIPLE POINT 37N 128W AND FARTHER WEST OF THAT IS AN
OCCLUDED LOW PRESSURE 32N 140W ALSO TRACKING EASTWARD. ALOFT IS A
LITTLE MORE INTERESTING AS SPLIT FLOW WITH A HIGH AMPLIFIED POLAR
JET (DIGGING SW THRU BC AND THEN RECURVING INTO NORCAL) IS SHOWING
SOME PHASING WITH THE SUB-TROPICAL JET ARRIVING FROM THE SW. THESE
UPPER LEVEL JET FEATURES/PHASING WILL AID IN OVERALL LARGE SCALE
ASCENT. ON TOP OF THIS FEATURES, PWAT SATELLITE IMAGERY SHOWS A
PINEAPPLE EXPRESS (AR) PLUME JUST SE OF HAWAII EXTENDING NORTH
ALONG THE SURFACE BOUNDARIES TO NORCAL.
SO WHAT DOES THIS MEAN AND HOW WILL IT IMPACT THE BAY AREA AND
CENTRAL COAST? THE UPSTREAM "TRIPLE POINT" LOW WILL MOVE EAST AND
HELP TO LIFT THE STATIONARY BOUNDARY SLIGHTLY, BUT ALSO ALLOW FOR
A MORE DEFINED SURFACE FRONT. THIS SURFACE ENHANCEMENT WILL BE
AIDED BY AN UPPER LEVEL JET EXIT REGION OVER NORCAL THIS EVENING.
LARGE SCALE FORCING, OROGRAPHIC ENHANCED, AND PWAT TRANSPORT WILL
LEAD TO HEAVIER RAIN SPREADING OVER THE NORTH BAY THIS EVENING.
COULD SEE SOME DECENT RAINFALL RATES OF 0.5" PER HR. RAINFALL
COVERAGE AND INTENSITY WILL GRADUALLY MOVE S AND E OVER THE REST
OF THE FORECAST AREA BY TUESDAY MORNING. NOT ONLY WILL RAIN
INCREASE THIS EVENING THROUGH EARLY TUESDAY, BUT THE WINDS WILL
TOO. THE WINDS WILL INCREASE RAPIDLY OVER THE NORTHERN COASTAL
WATERS THIS EVENING AND THEN SPREAD TO THE COASTAL AREAS MONTEREY
BAY NORTHWARD. A WIND ADV WAS ISSUED TO ACCOUNT FOR THIS INCREASE
IN WINDS.
EARLY TUESDAY WILL FEATURE A BRIEF "LULL" IN ACTIVITY AS THE
"TRIPLE POINT LOW" FADES WITH AN EXITING JET REGION ALOFT. THE
LULL WILL BE SHORT LIVED AS EVEN BETTER JET DYNAMICS ALOFT TAKE
AIM AT THE BAY AREA AND CENTRAL COAST TUESDAY MID MORNING THROUGH
TUESDAY EVENING. EXPECT ANOTHER RAPID INCREASE IN WINDS AND PRECIP
ON TUESDAY AS A COLD FRONT PUSHES THROUGH THE REGION. THIS WILL
BRING THE MOST WIDESPREAD AND INTENSE RAINFALL.
OF PARTICULAR CONCERN IS BETWEEN 18 AND 21 UTC TUESDAY, FLOW
THROUGH THE COLUMN INCREASES. IN FACT, EXAMINING THE WIND FIELD AT
300MB REVEALS A PHASED OR COUPLED JET TYPE PATTERN WITH A WIND
MAXIMA APPROACHING THE CA/OR COASTLINE WITH A BROADER FIELD OF
+120 KNOT MID LEVEL FLOW. IN RESPONSE, THE LOWEST 1 KM WIND FIELD
RESPONDS AND 925MB FLOW RAMPING UP TO AROUND 50 KNOTS. THIS IS
PARTICULARLY TRUE ALONG AND SOUTH OF THE TROUGH/COLD FRONTAL
BOUNDARY FOR REGIONS ALONG THE CENTRAL COAST AND BIG SUR
COASTLINE. WHILE INSTABILITY VALUES WILL BE ON THE LOWER END OF
THE SPECTRUM WITH UNDER 50 J/KG. FORECAST HODOGRAPHS INDICATE A
LARGE AMOUNT OF LOW LEVEL CURVATURE WITH 0-1 KM SHEAR IN EXCESS OF
30 KNOTS. THESE TYPES OF HIGH SHEAR, LOW CAPE REGIMES DO SUPPORT
BOTH THE TRANSFER OF DAMAGING 55+ MPH WINDS ALOFT DOWN TO THE
SURFACE AND IN SOME INSTANCES BRIEF TORNADOES. WE'LL CONTINUE TO
MONITOR TRENDS IN HIGH-RESOLUTION OUTPUT, BUT AS IT STANDS RIGHT
NOW, THE FAVORED REGION FOR ENHANCED WINDS OF 55+ MPH AND A
SLIGHTLY HIGHER TORNADO RISK WILL BE ALONG THE SAN FRANCISCO
PENINSULA COAST (PACIFIC OCEAN SIDE) DOWN TO THE BIG SUR COASTLINE
LATE TUESDAY MORNING AND THROUGH THE EVENING HOURS. THAT BEING
SAID, HAVE INCLUDED THUNDERSTORMS TO THE FORECAST FOR TUESDAY
WITH SPECIFIC WORDING HIGHLIGHTING GUSTY CONVECTIVE WINDS.
HEAVY RAIN WILL TRANSITION LATE TUESDAY TO MORE SHOWER ACTIVITY
FROM N TO S BEHIND THE DEPARTING COLD FRONT. RAINFALL AMOUNTS
TONIGHT THROUGH TUESDAY NIGHT WILL 4-6" NORTH BAY AND COASTAL MTS
(JACKPOT UP TO 9" ABOVE BIG SUR), 2-4" ELSEWHERE, WITH LESSER
AMOUNTS 0.75 TO 1.5" SANTA CLARA VALLEY/INTERIOR CENTRAL COAST.
IT GOES WITHOUT SAYING, BUT THESE ROUNDS OF INTENSE RAINFALL WILL
LEAD TO FLOODING CONCERNS, ESPECIALLY IN AREAS WHERE RAIN FELL
OVER THE WEEKEND. DO EXPECT FLOOD ADVISORIES TO BE ISSUES FOR
URBAN AND SMALL STREAM FLOODING CONCERNS. IF YOU ENCOUNTER
A FLOODED ROADWAY OR ROAD CLOSURE BARRICADES REMEMBER - TURN AROUND,
DON'T DROWN!
LONG TERM
ISSUED AT 240 PM PST MON FEB 3 2025
(TUESDAY NIGHT THROUGH NEXT SUNDAY)
WEDNESDAY CAN BE DESCRIBED AS ANOTHER LULL IN OVERALL ACTIVITY AS
ONE STORM/MOISTURE PLUME EXITS AND ANOTHER APPROACHES FROM THE
WEST.
THURSDAY AND FRIDAY...A SURFACE LOW WILL APPROACH THE CENTRAL
COAST. UNLIKE THE TUESDAY AR THIS SYSTEM WILL HAVE LESS SUPPORT
ALOFT AND TRACK A LITTLE FARTHER SOUTH. ADDITIONALLY, THE MOISTURE
TAP IS LESS WITH IVT/IWV VALUES SOLIDLY IN THE WEAK AR REALM.
THANKFULLY, THIS LOW ALSO APPEARS TO BE A FAST MOVER WITH HIGHEST
RAINFALL TOTALS NORTH BAY AND COASTAL MTS AROUND 1" WITH
0.25-0.75" ELSEWHERE. GIVEN THE MORE SOUTHERN TRACK THIS SYSTEM
WILL BE COLD WITH LOWERING SNOW LEVELS. SNOW LEVEL WILL LOWER N TO
S, BUT BY THE TIME THE LOWEST SNOW LEVELS ARRIVE THE PRECIP MAY BE
TAPERING OFF THURSDAY INTO FRIDAY. REGARDLESS, SOME WET SNOW WILL
BE POSSIBLE OVER THE HIGHER PEAKS THURSDAY INTO FRIDAY. NOT
EXPECTING MUCH IN THE WAY OF ACCUMULATION.
SPEAKING OF COLDER, THE PRECIP THREAT WILL QUICKLY TRANSITION TO A
TEMPERATURE THREAT NEXT WEEKEND. COLD ADVECTION ALOFT BEHIND THE
DEPARTING LOW COMBINED WITH CLEARING SKIES WILL LEAD TO SOME
CHILLY OVERNIGHT LOWS. BOTH SAT/SUN MORNINGS WILL FEATURE TEMPS
IN THE 30S (EVEN TOWARD THE COAST) WITH FAR INTERIOR IN THE 20S.
WILL LIKELY NEED A MIX OF FROST/FREEZE PRODUCTS.
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 1125 AM PST MON FEB 3 2025
A SECOND AND STRONGER ATMOSPHERIC RIVER AND ACCOMPANYING SURFACE
LOW WILL BRING HIGHER RAINFALL TOTALS AND AN INCREASED FLOOD RISK
ACROSS THE NORTH BAY, AND THE COASTAL RANGES OF THE BAY AREA AND
CENTRAL COAST THROUGH MIDWEEK. WPC (WEATHER PREDICTION CENTER)
HAS PLACED THE NORTH BAY IN A SLIGHT RISK (15%) OF EXCESSIVE
RAINFALL AND A MARGINAL RISK (5%) OVER THE SANTA CRUZ AND SANTA
LUCIA RANGES THROUGH 12Z TUESDAY (DAY 1). FOR DAY 2 (12Z TUESDAY
THROUGH 12Z WEDNESDAY) THE SLIGHT RISK OF EXCESSIVE RAINFALL WILL
CONTINUE OVER THE NORTH BAY AND HAS BEEN EXTENDED SOUTHWARD ACROSS
THE SANTA CRUZ AND SANTA LUCIA RANGES WITH A MARGINAL RISK ACROSS
THE REST OF THE HSA.
A FLOOD WATCH WILL GO INTO EFFECT AT 4 PM PST THIS AFTERNOON AND
WILL REMAIN IN EFFECT THROUGH 4 AM PST WEDNESDAY. THE URBAN AND
SMALL STREAM FLOOD ADVISORY OVER CENTRAL SONOMA WAS EXTENDED
THROUGH 8:45 PM TONIGHT FOR CONTINUED FLOODING IMPACTS AS WELL AS
THE IMPACTS ASSOCIATED WITH THE EXPECTED RAINFALL LATER TODAY. THE
FLOOD ADVISORY IS EXPECTED TO BE EXTENDED BEYOND TONIGHT AT THE
NEXT ISSUANCE.
THE LATEST FORECAST FROM THE CNRFC KEEP THE MAIN STEM RIVERS
BELOW FLOOD STAGE ACROSS THE NORTH BAY (RUSSIAN AND NAPA).
HOWEVER, THE EXCEEDANCE PROBABILITIES (OF RISING ABOVE FLOOD
STAGE) HAVE INCREASED 5 TO 10% OVER THE MAIN STEM RIVER FORECAST
POINTS.
OTHER NON-MAIN STEM FORECAST POINTS TO KEEP AN EYE ON ARE
MWEC1 - MARK WEST CREEK AT MIRABEL HEIGHTS
GRQC1 - GREEN VALLEY CREEK AT MARTINELLI ROAD
CTIC1- LAGUNA DE SANTA ROSA AT STONY POINT ROAD NEAR COTATI. THESE
POINTS WILL REMAIN IN OR EXCEED MINOR FLOOD STAGE BETWEEN NOW AND
FRIDAY. THESE LOCATIONS WILL BE HANDLED THROUGH ONGOING FLOOD
ADVISORIES.
CW
MTR WATCHES/WARNINGS/ADVISORIES
CA...WIND ADVISORY UNTIL 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 UNTIL 3 AM PST TUESDAY FOR SF BAY N OF BAY BRIDGE.
GALE WARNING UNTIL 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 UNTIL 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...MM/LB
LONG TERM....MM
AVIATION...JM
MARINE...JM
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