407
FXUS66 KMTR 311832
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
1032 AM PST FRI JAN 31 2025
..NEW AVIATION
SYNOPSIS
ISSUED AT 302 AM PST FRI JAN 31 2025
THE FIRST OF NUMEROUS ROUNDS OF RAINFALL HAS BEGUN ACROSS THE
NORTH BAY AND WILL GRADUALLY SPREAD SOUTHWARDS AND INLAND ACROSS
THE REST OF OUR AREA LATER TODAY INTO SATURDAY. SCATTERED LIGHT
RAIN LINGERS ON SUNDAY OUT AHEAD OF A STRONGER, MORE IMPACTFUL
SYSTEM FOR THE BEGINNING OF NEXT WEEK AND BEYOND.
UPDATE
ISSUED AT 828 AM PST FRI JAN 31 2025
FORECAST STILL ON TRACK THIS MORNING WITH RAIN SPREADING ACROSS
THE NORTH BAY AND INTO THE BAY AREA. AMOUNTS MOSTLY IN THE RANGE
OF A FEW HUNDREDTHS TO A TENTH OF AN INCH SO FAR. BRIEF HEAVIER
RAINFALL RATES EXPECTED IN THE VICINITY OF SAN FRANCISCO WITHIN
THE 10 AM HOUR...GENERALLY IN THE BALLPARK OF 0.3-0.5 IN/HR.
LIGHT TO MODERATE RAIN WILL CONTINUE ACROSS THE NORTH BAY MOST OF
THE DAY, BUT RAINFALL RATES ARE EXPECTED TO INCREASE ALONG THE
SONOMA AND MARIN COASTAL AREAS BY ABOUT THE 1-2 PM TIME FRAME,
ALSO ON THE ORDER OF 0.3-0.5 IN/HR, BUT PERHAPS LASTING FOR A
LONGER PERIOD THROUGH MID-AFTERNOON.
BEHRINGER
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 302 AM PST FRI JAN 31 2025
THE LONG AWAITED RETURN OF RAIN HAS BEGUN WITH KMUX SHOWING
PRECIPITATION MOVING INTO NORTHERN CALIFORNIA AND ALONG OUR COASTAL
WATERS. THE LAST TIME SIGNIFICANT RAINFALL WAS OBSERVED WAS 1/3/2025
WHEN, AMONG OTHERS, SANTA ROSA SAW 0.49", OAKLAND SAW 0.20", AND SAN
FRANCISCO 0.18". TOTALS FROM THIS EVENT WILL BE HIGHER THAN THOSE
OBSERVED IN EARLY JANUARY AND SHOULD MAKE A DENT IN WHERE WE STAND
WITH OUR WATER YEAR PERCENT OF NORMAL TOTALS. A LOOK AT THE CNRFC
SHOWS MANY SITES ACROSS THE NORTH BAY ARE AT OR ABOVE 100% OF
NORMAL. THE STORY CHANGES, HOWEVER, WHEN YOU SHIFT SOUTHWARD WITH
MOST SITES ACROSS THE BAY AREA ONLY AT 50-70% OF NORMAL RAINFALL
TOTALS FOR THE WATER YEAR. IN FACT, THE FARTHER SOUTH YOU SHIFT
(SOUTH BAY INTO CENTRAL COAST) THE MORE SITES WE START TO SEE WITH
RAINFALL TOTALS THAT ARE ONLY 20-30% OF NORMAL ACROSS THE INTERIOR
AND 50-70% OF NORMAL ALONG THE COAST FOR THE WATER YEAR.
FOR FRIDAY, SCATTERED SHOWERS WILL MOVE INTO THE NORTH BAY EARLY
THIS MORNING BEFORE BECOMING MORE WIDESPREAD ACROSS THE BAY AREA
LATE THIS MORNING INTO THE EARLY AFTERNOON. TOTALS WILL BE HIGHEST
ACROSS THE NORTH BAY WHERE AN INITIAL 0.5"-1.5" IS POSSIBLE FRIDAY
WHILE THE REST OF THE BAY AREA MAY SEE UP TO 0.5" ON FRIDAY. SHOWERS
WILL FILTER INTO THE CENTRAL COAST BY THE LATE AFTERNOON/EVENING
HOURS BUT TOTALS ARE EXPECTED TO BE MUCH LESS IMPRESSIVE, WITH ONLY
UP TO 0.1" EXPECTED FRIDAY. A DAY ONE MARGINAL RISK OF EXCESSIVE
RAINFALL - DEFINED AS A AT LEAST 5% CHANCE OF RAINFALL EXCEEDING
FLASH FLOOD GUIDANCE WITHIN 25 MILES OF A POINT - HAS BEEN ISSUED
FOR THE NORTH BAY AND PORTIONS OF THE BAY AREA (INCLUDING SAN
FRANCISCO AND OAKLAND). AS SHOWERS RETURN, WINDS WILL PICK UP ALONG
THE COAST AND ACROSS AREAS OF ELEVATED TERRAIN. THE STRONGEST GUSTS
WILL GENERALLY BE BETWEEN 25 TO 30 MPH BUT ISOLATED LOCALLY STRONGER
GUSTS MAY DEVELOP. A FLOOD WATCH GOES INTO EFFECT FOR THE BAY AREA
AT 12PM PST FRIDAY AND CONTINUES THROUGH 10 PM PST SATURDAY. WHILE
INITIAL FLOODING CONCERNS REMAIN LOWER DUE TO THE RECENT DRY SPELL,
FLOODING CONCERNS ARE LIKELY TO INCREASE MOVING THROUGH THE WEEKEND
INTO NEXT WEEK AS WE SEE COMPOUNDING DAYS OF WET WEATHER ACROSS THE
REGION. FLOODING IS MOST LIKELY TO OCCUR ACROSS THE NORTH BAY, WHERE
THE HIGHEST RAINFALL TOTALS ARE EXPECTED, BUT NUISANCE FLOODING WILL
BECOME MORE LIKELY ACROSS THE REST OF THE BAY AREA AS WE HEAD INTO
THE WEEKEND.
WONDERING WHAT THE MORAL OF THE STORY IS? FOLKS IN THE NORTH BAY,
PREPARATIONS FOR THE UPCOMING RAIN SHOULD ALREADY BE COMPLETED AND
RESIDENTS SHOULD BE PREPARED FOR ANY MINOR NUISANCE FLOODING THAT
MAY OCCUR. FOLKS IN THE BAY AREA AND CENTRAL COAST SHOULD TAKE CARE
OF ANY REMAINING OUTDOOR PREPARATIONS TODAY BEFORE MORE MODERATE
RAIN MOVES IN OVER THE WEEKEND AND INTO NEXT WEEK. REMEMBER TO TAKE
CARE WHILE DRIVING AS ROADS MAY BE SLICKER THAN NORMAL DURING THE
FIRST SIGNIFICANT RAINS AFTER A DRY SPELL AND KEEP AN EYE OUT FOR
NUISANCE FLOODING/PONDING ON THE ROADWAY. IF YOU ENCOUNTER FLOODED
ROADWAYS, TURN AROUND, DON'T DROWN!
LONG TERM
(SATURDAY THROUGH THURSDAY)
ISSUED AT 302 AM PST FRI JAN 31 2025
IF YOU'VE BEEN SORELY MISSING THE RAIN FOR THE LAST MONTH, THIS
UPCOMING WEEK IS FOR YOU! CONTINUING FROM OUR FRIDAY SYSTEM, MORE
WIDESPREAD, MODERATE RAIN MOVES IN ON SATURDAY WITH THE HEAVIEST
SHOWERS EXPECTED SATURDAY MORNING INTO THE AFTERNOON. CURRENT
GUIDANCE SUGGESTS 1.0"-2.0" ARE POSSIBLE ACROSS THE NORTH BAY, 0.5"-
1.5" ACROSS THE REST OF THE BAY AREA, AND UP TO 0.5" FOR THE CENTRAL
COAST ON SATURDAY. A SLIGHT RISK (AT LEAST 15% CHANCE) OF EXCESSIVE
RAINFALL IS IN EFFECT FOR THE NORTH BAY AND PORTIONS OF THE BAY AREA
(INCLUDING THE CITY OF SAN FRANCISCO) FOR SATURDAY WITH A MARGINAL
RISK OF EXCESSIVE RAINFALL IN EFFECT FOR PORTIONS OF THE SOUTH BAY
AND CENTRAL COAST. HEADING INTO SUNDAY, GUIDANCE SUGGESTS RAINFALL
WILL BE LIGHTER AND MORE CONCENTRATED OVER THE NORTH BAY AS THE
MOISTURE PLUME SHIFTS SLIGHTLY NORTHWARD. AS SUCH, THE WPC HAS
ISSUED A DAY 3 MARGINAL RISK OF EXCESSIVE RAINFALL FOR THE NORTH BAY
ON SUNDAY. THE NEXT ROUND OF WIDESPREAD MODERATE SHOWERS BEGINS
MONDAY AS ANOTHER UPPER LEVEL LOW AND ASSOCIATED SURFACE LOW
PRESSURE SYSTEM MOVE THROUGH THE BAY AREA. THE DAY FOUR (MONDAY) WPC
EXCESSIVE RAIN OUTLOOK SHIFTS THE NORTH BAY INTO A SLIGHT RISK OF
EXCESSIVE RAINFALL AND PORTIONS OF THE BAY AREA INTO A MARGINAL
RISK. BY DAY FIVE (TUESDAY), A MORE WIDESPREAD MARGINAL RISK OF
EXCESSIVE RAINFALL IS EXPECTED ACROSS THE ENTIRE BAY AREA AND
CENTRAL COAST. WHEN ALL IS SAID AND DONE, FROM FRIDAY TO THURSDAY,
THE NORTH BAY WILL SEE ROUGHLY BETWEEN 5"-8" OF RAIN, THE REMAINDER
OF THE BAY AREA WILL SEE BETWEEN 3"-5", AND UP TO 2.5" IS POSSIBLE
ACROSS THE CENTRAL COAST. LOCALLY HIGHER TOTALS ARE POSSIBLE
THROUGHOUT THE ELEVATED TERRAIN OF THE SANTA CRUZ MOUNTAINS AND THE
SANTA LUCIA RANGE WITH OVERALL TOTALS BETWEEN 4"-5" POSSIBLE BY LATE
NEXT WEEK.
GUSTY WINDS ARE EXPECTED TO CONTINUE THROUGH THE WEEK WITH NBM AND
LOCAL WRF GUIDANCE HIGHLIGHTING TUESDAY AND WEDNESDAY FOR
PARTICULARLY WINDY CONDITIONS. DAYTIME TEMPERATURES WILL BE IN THE
50S TO LOW 60S THROUGH MIDWEEK WHILE MORNING LOWS HOVER IN THE 40S
TO LOW 50S. COLD MORNINGS RETURN AGAIN WEDNESDAY THROUGH THE END OF
THE FORECAST PERIOD, WITH LOWS TO DROP INTO THE 30S AGAIN. THIS
COMBINATION OF WET WEATHER, GUSTIER WINDS, AND COLD MORNINGS MAY
CREATE A SETUP HAZARDOUS FOR THOSE WITHOUT ADEQUATE HEAT OR SHELTER
MID TO LATE NEXT WEEK.
AVIATION
(18Z TAFS)
ISSUED AT 1010 AM PST FRI JAN 31 2025
MVFR TO VFR CEILINGS ARE EXPECTED TO CONTINUE THROUGH MOST OF THE
DAY INTO THE EARLY EVENING HOURS, WHEN CONDITIONS WILL BECOME
MORE OF A MIX OF MVFR TO IFR/LIFR FOR THE OVERNIGHT INTO EARLY
SATURDAY MORNING. ALONG WITH THE MVFR/IFR CEILINGS, EXPECT AN
INCREASE IN GUSTY S/SE WINDS.
VICINITY OF SFO...MVFR TO VFR CONDITIONS HEADING INTO THE AM RUSH
WITH CIGS HOVERING AROUND 3K FEET. LIGHT RAIN ARRIVING AROUND
17-18Z AND STEADIER RAIN BY THE EVENING RUSH. WET RUNWAYS AND
GUSTY SOUTHERLY WINDS COULD CAUSE ISSUES EARLY SATURDAY. NO AWW
RIGHT NOW, BUT WILL WATCH CLOSELY.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...EXPECT MVFR TO VFR CONDITIONS TO PERSIST
THROUGH THE REMAINDER OF THE DAY INTO THE EARLY EVENING, WHEN
CEILINGS WILL BECOME PRIMARILY MVFR/IFR THROUGH THE OVERNIGHT INTO
SATURDAY MORNING WITH PERIODS OF ON AND OFF RAIN OCCASIONALLY
DROPPING VISIBILITY.
MARINE
(TODAY THROUGH WEDNESDAY)
ISSUED AT 338 AM PST FRI JAN 31 2025
UNSETTLED WEATHER RETURNS TO THE COASTAL WATERS AS A SERIES OF
SYSTEM WILL BRING RAIN, CHANCE FOR THUNDERSTORMS, AND GUSTY WINDS
THIS WEEKEND AND NEXT WEEK. WINDS WILL INCREASE LATER ON FRIDAY
AND REMAIN GUSTY INTO NEXT WEDNESDAY. THE GUSTY WINDS WILL RESULT
IN HAZARDOUS MARINE CONDITIONS WITH FRESH SWELL AND STEEP WIND
WAVES.
MTR WATCHES/WARNINGS/ADVISORIES
CA...FLOOD WATCH THROUGH SUNDAY EVENING FOR CAZ006-502>506-508>510-
512>515-529.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PST SATURDAY FOR SF BAY N OF BAY
BRIDGE.
SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 9 AM PST SATURDAY
FOR MRY BAY.
SMALL CRAFT ADVISORY UNTIL 9 PM PST THIS EVENING FOR PT ARENA TO
PT REYES 0-10 NM-PT ARENA TO PT REYES 10-60 NM.
SMALL CRAFT ADVISORY UNTIL 3 PM PST SATURDAY FOR PIGEON PT TO PT
PINOS 10-60 NM-PT REYES TO PIGEON PT 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 3 PM PST
SATURDAY FOR PIGEON PT TO PT PINOS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 3 PM PST SATURDAY
FOR PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...JM
MARINE...MM
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