230
FXUS66 KMTR 021055
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
255 AM PST SUN FEB 2 2025
..NEW SYNOPSIS, SHORT TERM, LONG TERM
SYNOPSIS
ISSUED AT 248 AM PST SUN FEB 2 2025
LIGHTER RAIN IS EXPECTED TODAY BEFORE MORE WIDESPREAD MODERATE TO
HEAVY RAIN RETURNS MONDAY INTO TUESDAY AND WET WEATHER CONTINUES
THROUGH THE END OF THE WEEK. A FLOOD WATCH REMAINS IN EFFECT
THROUGH 10 PM SUNDAY AND A FLOOD ADVISORY CONTINUES FOR PORTIONS
OF SONOMA COUNTY THROUGH 4 AM SUNDAY. ADDITIONAL FLOOD PRODUCTS
ARE LIKELY TO BE ISSUED THIS WEEK AS INCREASED RUNOFF WILL RESULT
IN ADDITIONAL NUISANCE FLOODING AND SEVERAL RIVERS HAVE THE
POTENTIAL TO RISE ABOVE FLOOD STAGE (SEE HYDROLOGY SECTION).
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 248 AM PST SUN FEB 2 2025
WITH THE FIRST ROUND OF RAIN FROM THE ATMOSPHERIC RIVER BEHIND US,
HOW MUCH RAIN HAVE WE SEEN SO FAR? OVER THE LAST 48 HOURS THE NORTH
BAY HAS GENERALLY SEEN BETWEEN 2"-4" OF RAIN WITH LOCALLY HIGHER
TOTALS POSSIBLE WHERE OROGRAPHIC UPLIFT IS FAVORED (SEE MOUNT TAM.
CLOCKING IN WITH A TWO DAY TOTAL OF 6.12"). ACROSS THE REST OF THE
BAY AREA TOTALS GENERALLY RANGED FROM 0.5" TO 1.0" WHILE ALMOST
EVERYONE IN THE CENTRAL COAST SAW LESS THAN 0.25". SUNDAY IS STILL
EXPECTED TO BE A TRANSITION DAY BETWEEN OUR FIRST ROUND OF RAIN
(FRIDAY TO SATURDAY) AND OUR SECOND ROUND (MONDAY TO TUESDAY) WITH
WIDESPREAD LIGHT RAIN ANTICIPATED TO CONTINUE TODAY. THIS WILL
GENERALLY AMOUNT TO UP TO HALF AN INCH OF ADDITIONAL RAIN ACROSS THE
BAY AREA. THE EXCEPTION TO THIS WILL BE THE FAR NORTHERN PORTIONS OF
SONOMA AND NAPA COUNTIES WHERE UP TO 2" OF ADDITIONAL RAIN ARE
EXPECTED. AS HAS BEEN PREVIOUSLY MENTIONED, THE MAIN MOISTURE PLUME
IS EXPECTED TO SHIFT NORTHWARD WITH THE HIGHEST PRECIPITABLE WATER
TOTALS (>1.0") LOCATED ALONG THE BORDER OF SONOMA AND MENDOCINO
COUNTIES. FARTHER SOUTH, (SOUTHERN PORTIONS OF THE NORTH BAY INTO
THE EAST BAY AND SAN MATEO PENINSULA) PRECIPITABLE WATER VALUES WILL
BE LESS THAN OR EQUAL TO 1.0" FOR MUCH OF THE DAY. GIVEN THAT
PRECIPITABLE WATER IS REFLECTIVE OF THE TOTAL AMOUNT OF AVAILABLE
MOISTURE (IN AN ATMOSPHERIC COLUMN) THAT COULD FALL AS RAIN, IT CAN
GIVE US AN IDEA WHERE THE HIGHEST RAIN TOTALS ARE LIKELY TO BE. AS
SUCH, THE HEAVIEST RAIN TODAY WILL BE LOCATED OVER THE NORTH BAY
(PRIMARILY SONOMA AND NAPA COUNTIES) WITH LIGHTER RAIN EXPECTED
THROUGHOUT THE REST OF THE BAY AREA. THE WPC HAS ISSUED A SLIGHT
RISK (15% CHANCE) OF EXCESSIVE RAINFALL EXCEEDING FLASH FLOOD
GUIDANCE ACROSS NORTHERN SONOMA AND NAPA COUNTIES AND A MARGINAL
RISK (5%) OVER SOUTHERN SONOMA/NAPA AND MARIN COUNTIES ON SUNDAY. A
FLOOD WATCH REMAINS IN EFFECT THROUGH 10 PM SUNDAY FOR THE BAY AREA.
FLOODING CONCERNS ARE INCREASING, PARTICULARLY ACROSS THE NORTH BAY,
SUNDAY INTO NEXT WEEK. PRIOR TO FRIDAY, SOILS WERE FAIRLY DRY ACROSS
THE REGION BUT THE RAIN WE RECEIVED FRIDAY INTO SATURDAY WAS ENOUGH
TO SATURATE SOILS ACROSS PORTIONS OF THE BAY AREA. AS SOILS BECOME
MORE SATURATED, THEY ARE ABLE TO ABSORB LESS WATER AND RUNOFF WILL
INCREASE. THIS WILL LEAD TO INCREASED CHANCES FOR NUISANCE FLOODING
ON STREETS/LOW LYING AREAS AND CONTRIBUTE TO RISES IN
STREAMS/CREEKS. THIS IS PARTICULARLY TRUE FOR THE NORTH BAY WHERE WE
HAVE SEEN THE HIGHEST RAIN TOTALS AND EXPECT RAIN TO CONTINUE
TRAINING OVER THE AREA. FLOODING CONCERNS WILL CONTINUE TO INCREASE
ACROSS THE NORTH BAY TODAY BUT WILL REALLY START TO INCREASE
MONDAY/TUESDAY AS WE SEE THE NEXT ROUND OF MODERATE TO HEAVY RAIN.
FOR MORE INFORMATION ON CONCERNS RELATED TO MAINSTREAM RIVER
FLOODING, SEE THE HYDROLOGY SECTION BELOW. ADDITIONALLY, THE
COMBINATION OF LOCALLY GUSTY WINDS (ELEVATED TERRAIN AND ALONG THE
COAST) AND SATURATED SOILS MAY RESULT IN A FEW TREES BEING
KNOCKED OVER OR DAMAGED. OVERNIGHT TEMPERATURES WILL LARGELY
REMAIN IN THE 40S TO LOW 50S WITH DAYTIME HIGH TEMPERATURES IN THE
UPPER 50S TO LOW 60S.
LONG TERM
(MONDAY THROUGH SATURDAY)
ISSUED AT 248 AM PST SUN FEB 2 2025
LIGHT SHOWERS CONTINUE SUNDAY INTO MONDAY WITH THE NEXT ROUND OF
HIGHER INTENSITY RAIN RETURNING LATE MONDAY MORNING/MONDAY
AFTERNOON. TAKING A LOOK AT THE SYNOPTIC PATTERN, AN UPPER LEVEL
TROUGH OFF OF THE PNW AND AN UPPER LEVEL RIDGE OVER SOUTHERN CA HAVE
IN PART KEPT OUR MOISTURE PLUME TIGHTER AND PUSHED FARTHER NORTH
THIS WEEKEND. BY MONDAY, THE UPPER LEVEL TROUGH WILL DEEPEN OVER THE
PNW, PUSHING FARTHER INTO NORTHERN CA, AND RIDGING OVER SOUTHERN CA
WILL START TO SHIFT EASTWARD. THIS WILL ALLOW FOR THE MOISTURE PLUME
TO WIDEN AND SHIFT SOUTHWARDS AGAIN LATE MONDAY MORNING/MONDAY
AFTERNOON WITH PRECIPITABLE WATER VALUES GENERALLY INCREASING TO
GREATER THAN 1" ACROSS THE REGION. AT THE SAME TIME, THE STATIONARY
FRONT OVER THE NORTH BAY WILL GIVE WAY TO A MORE PROGRESSIVE COLD
FRONT THAT WILL MOVE THROUGH THE BAY AREA MONDAY INTO TUESDAY. RAIN
WILL START TO PICK UP IN INTENSITY BY MID TO LATE MONDAY MORNING
WITH THE INITIAL HEAVIEST RAIN LOCATED IN THE NORTH BAY. HIGH
RESOLUTION MODELS ARE STARTING TO SHOW PRECIPITATION LINGERING OVER
THE BAY AREA (SOUTH OF THE NORTH BAY) AND SANTA CRUZ MOUNTAINS
OVERNIGHT MONDAY THROUGH TUESDAY MORNING. TOTALS HAVE TRENDED
UPWARDS MONDAY INTO TUESDAY WITH AN ADDITIONAL 3"-4" POSSIBLE ACROSS
THE NORTH BAY, 2"-3" ACROSS THE REST OF THE BAY AREA, AND 1"-3"
ACROSS THE CENTRAL COAST. LOCALLY HIGHER TOTALS (4"+) ARE POSSIBLE
IN AREAS WHERE UPSLOPING IS FAVORED (NORTH BAY AND COASTAL
MOUNTAINS). A SLIGHT CHANCE (<10%) OF THUNDERSTORMS CONTINUES TO BE
MONITORED FOR TUESDAY MORNING BUT THE PROBABILITY HAS BEEN TRENDING
DOWNWARDS RECENTLY.
WET WEATHER WILL THEN CONTINUE WEDNESDAY THROUGH THE END OF THE WEEK
AS TROUGHING PERSISTS OVER THE WEST COAST. LATE WEEK RAIN TOTALS
WILL BE LOWER, HOWEVER, WITH MOST AREAS SEEING LESS THAN 1" OF
ADDITIONAL RAIN. THE EXCEPTION, AGAIN, WILL BE WHERE UPSLOPING IS
FAVORED WITHIN THE COASTAL MOUNTAINS WHERE TOTALS WILL BE BETWEEN 1"-
2". THIS SECOND SYSTEM WILL BE COLDER WITH MORNING LOWS EXPECTED TO
DROP INTO THE MID 30S TO LOW 40S ACROSS THE REGION. THE COMBINATION
OF DAMP WEATHER AND COOLER TEMPERATURES MAY CREATE CONDITIONS THAT
ARE PARTICULARLY HAZARDOUS FOR PEOPLE WITHOUT ACCESS TO ADEQUATE HEAT
OR SHELTER.
IT IS WORTH NOTING THAT THE WPC MAINTAINS A SLIGHT TO MARGINAL RISK
OF EXCESSIVE RAINFALL FOR THE BAY AREA AND PORTIONS OF THE CENTRAL
COAST THROUGH TUESDAY AND AGAIN ON THURSDAY. FLOODING CONCERNS WILL
REMAIN ELEVATED THROUGH THE WEEK AS OUR INITIAL RAINFALL FROM FRIDAY
TO SATURDAY HAVE CAUSED SOILS TO SATURATE. THIS WILL LEAD TO
INCREASED SURFACE RUNOFF AND IS LIKELY TO LEAD TO ADDITIONAL FLOOD
RELATED PRODUCTS AS WE MOVE THROUGH OUR NEXT TWO ROUNDS OF WET
WEATHER. IN ADDITION, GUSTY WINDS ARE LIKELY TO PERSIST FOR COASTAL
AREAS AND ELEVATED TERRAIN MONDAY THROUGH WEDNESDAY WITH THE
STRONGEST GUSTS LIKELY TO DEVELOP AHEAD OF/AROUND THE TIME OF COLD
FRONTAL PASSAGE MONDAY INTO TUESDAY. THIS MAY RESULT IN A FEW TREES
BEING KNOCKED OVER AND INCREASED POTENTIAL FOR POWER OUTAGES TO
OCCUR. MAKE SURE TO HAVE MULTIPLE WAYS TO RECEIVE WARNINGS AND STAY
UP TO DATE ON THE FORECAST AS WE MOVE THROUGH THE UPCOMING WEEK.
AVIATION
(06Z TAFS)
ISSUED AT 1219 AM PST SUN FEB 2 2025
UPDATE: FOG AND DENSE FOG (SURFACE VISIBILITY LESS THAN 1/4 MILE)
HAS DEVELOPED IN THE VICINITY OF KSNS AND KCVH. A SURFACE BASED
AREA OF POST SUNSET (LOSS OF HEAT) AND SLIGHTLY RAIN COOLED AND
STAGNANT AIR, VERY LIKELY WITHIN RESIDUAL (DRY) CONTINENTAL AIR
THAT HAS RECENTLY REACHED THE DEWPOINT TEMPERATURE (SATURATION)
HAS RESULTED IN FOG /VLIFR-IFR/. FOG AND DENSE FOG /VLIFR-IFR/
LIKELY EXTENDS ALONG BOTH KSNS AND KCVH VALLEY FLOORS, FOG CONTINUING
THIS MORNING IF UNTIL MIXING WINDS DEVELOP. AT THE MOMENT MODEL
FORECASTS ARE OVER-FORECASTING SURFACE WINDS AND THE POTENTIAL FOR
MIXING OUT FOG. MODEL GUIDANCE SHOWS INCREASING SE WINDS E.G.
VICINITY KSNS THROUGH THIS MORNING WHICH SHOULD HELP MIX OUT THE
FOG CLOSER TO DAYBREAK OR EARLIER.
FROM THE PREVIOUS DISCUSSION: LIGHT RAIN SHOWER ACTIVITY WILL
CONTINUE OVERNIGHT, PARTICULARLY IN THE BAY AREA. A DEFINITIVE
RAIN BAND WILL DROP FROM THE NORTHWEST TOMORROW MORNING, LOSING
ITS STEAM AS IT DROPS TO THE SOUTHEAST. AFTER THAT, RAIN SHOWERS
WILL CONTINUE AGAIN PARTICULARLY IN THE BAY AREA. SOUTHERLY WINDS
WILL CONTINUE TO BE STRONG AND GUSTY THROUGH THE TAF PERIOD. ALL
BAY AREA TERMINALS ARE EXPECTED TO REMAIN SUB-VFR THROUGH THE TAF
PERIOD, ALTHOUGH BRIEF PERIODS OF VFR CONDITIONS MAY BE OBSERVED
TOMORROW AFTERNOON.
VICINITY OF SFO...CURRENTLY MVFR WITH SOUTHERLY WINDS. RAIN
SHOWER ACTIVITY WILL CONTINUE TO DIMINISH THROUGH THE EVENING.
A RAIN BAND WILL MOVE THROUGH MID-MORNING TOMORROW WITH RAIN
SHOWERS TO FOLLOW. STRONG AND GUSTY SOUTHERLY WINDS WILL PREVAIL
THROUGH THE TAF PERIOD.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...UPDATED: THERE ARE LARGELY VARIABLE
WEATHER CONDITIONS CURRENTLY WITH FOG AND DENSE FOG (SURFACE
VISIBILITY LESS THAN 1/4 MILE) IN THE VICINITY OF KSNS TO IFR
CEILINGS KWVI AND VFR VICINITY KMRY. A SURFACE BASED AREA OF POST
SUNSET (LOSS OF HEAT) AND SLIGHTLY RAIN COOLED AND STAGNANT AIR,
VERY LIKELY WITHIN RESIDUAL (DRY) CONTINENTAL AIR HAS RECENTLY
REACHED THE DEWPOINT TEMPERATURE (SATURATION) RESULTING IN FOG
/VLIFR-IFR/ VICINITY KSNS. CAVEAT, FOG AND DENSE FOG /VLIFR-IFR/
MAY BE PRESENT ACROSS THE SALINAS VALLEY THROUGH EARLY SUNDAY
MORNING, IF UNTIL MIXING WINDS DEVELOP. AT THE MOMENT MODEL
FORECASTS ARE OVER-FORECASTING SURFACE WINDS AT KSNS AND THE
AFOREMENTIONED POOL OF FOG AND DENSE FOG WILL POTENTIALLY
PREDOMINATE AT KSNS THROUGH 12Z THIS MORNING. MODEL GUIDANCE
SHOWS INCREASING SE WINDS VICINITY KSNS THROUGH THIS MORNING WHICH
SHOULD HELP MIX OUT THE FOG CLOSER TO DAYBREAK OR EARLIER.
ADDITIONAL FROM THE PREVIOUS DISCUSSION: THERE STILL MAY BE A
BRIEF REDUCTION IN FLIGHT CATEGORY IF A RAIN SHOWER PASSES OVER
THE TERMINAL; HOWEVER, RAIN SHOWER ACTIVITY IS LARGELY EXPECTED TO
REMAIN CONFINED TO THE NORTH OF THE TERMINALS WITH NORTHEASTWARD
MOTION. WINDS WILL PREVAIL OUT OF THE SOUTH FOR MRY WITH SNS
RETURNING TO DRAINAGE FLOW TONIGHT AND ONSHORE FLOW TOMORROW
AFTERNOON.
MARINE
(TONIGHT THROUGH NEXT FRIDAY)
ISSUED AT 924 PM PST SAT FEB 1 2025
STRONG AND GUSTY SOUTHERLY WINDS WILL PREVAIL THROUGH TUESDAY WITH
GALE FORCE GUSTS EXPECTED MONDAY AND TUESDAY. SIGNIFICANT WAVE
HEIGHTS WILL REMAIN MODERATE TO ROUGH, SLIGHTLY BUILDING THROUGH
MONDAY. RAINFALL IS EXPECTED THROUGH FRIDAY.
HYDROLOGY
ISSUED AT 924 PM PST SAT FEB 1 2025
AN ATMOSPHERIC RIVER WILL BRING PERIODS OF LIGHT TO MODERATE
RAINFALL THROUGH NEXT WEEK. THIS WILL RESULT IN AN INCREASED RISK
FOR RAPID RISES IN NORTH BAY RIVERS AND THE ASSOCIATED CREEKS AND
STREAMS. WHILE UNCERTAINTY EXISTS, THE PROBABILITIES OF EXCEEDING
FLOOD THRESHOLDS HAVE INCREASED ACROSS SEVERAL RIVERS IN THE NORTH
BAY. THE FIRST STORM THAT IS CURRENTLY MOVING INTO THE NORTH BAY IS
EXPECTED TO PRIME THE SOILS OVER THE WEEKEND RESULTING IN QUICKER
AND MORE NOTEWORTHY RISES OF AREA STREAMS AND CREEKS FOR THE SECOND
ROUND OF RAIN THAT IS PROGGED TO IMPACT THE NORTH BAY MONDAY INTO
TUESDAY. THE HIGHER ELEVATIONS OF THE NORTH BAY WILL LIKELY
ACCUMULATE AROUND 8 TO 11 INCHES OF (STORM TOTAL) PRECIPITATION
WHILE NORTH BAY VALLEYS WILL LIKELY ACCUMULATE AROUND 4 TO 6 INCHES
OF (STORM TOTAL) PRECIPITATION. SHALLOW LANDSLIDES WILL BE POSSIBLE
IN COASTAL AREAS OF THE NORTH BAY. THE THREAT WILL EXTEND SOUTHWARD
TO HIGHER ELEVATIONS OF THE BAY AREA, PARTICULARLY THE SANTA CRUZ
MOUNTAINS BY TUESDAY.
DETERMINISTIC FORECASTS KEEP MAINSTEM RIVERS BELOW FLOOD STAGE;
HOWEVER, THE EXCEEDANCE PROBABILITIES (OF RISING ABOVE FLOOD STAGE)
FOR REACHING FLOOD THRESHOLDS ARE INCREASING TUESDAY AND WEDNESDAY
ACROSS THE NORTH BAY. THE RUSSIAN RIVER AT GUERNEVILLE - GUEC1 HAS A
50% PROBABILITY OF EXCEEDING ACTION/MONITOR STAGE AND A 36%
PROBABILITY OF EXCEEDING MINOR FLOOD STAGE. SHEC1 - NAPA NEAR
SAINT HELENA HAS A 34% PROBABILITY OF EXCEEDING ACTION/MONITOR
STAGE AND A 23% PROBABILITY OF EXCEEDING MINOR FLOOD STAGE. APCC1 -
NAPA NEAR NAPA HAS A 34% PROBABILITY OF EXCEEDING ACTION/MONITOR
STAGE AND A 20% PROBABILITY OF EXCEEDING MINOR FLOOD STAGE. OTHER
POINTS THAT SHOW A HIGH PROBABILITY OF REACHING ACTION/MONITOR OR
MINOR FLOOD STAGE ARE: CTIC1 - LAGUNA DE SANTA ROSA AT STONY
POINT ROAD NEAR COTATI HAS A GREATER THAN 97.5% PROBABILITY OF
REACHING MINOR FLOOD STAGE, MWEC1 - MARK WEST CREEK AT MIRABEL
HEIGHTS HAS A GREATER THAN 97.5% PROBABILITY OF REACHING
ACTION/MONITOR STAGE AND A 95% PROBABILITY OF REACHING MINOR
FLOOD STAGE, AND GEYC1 - RUSSIAN RIVER AT GEYSERVILLE HAS A 59%
PROBABILITY OF REACHING ACTION/MONITOR STAGE AND A 43% PROBABILITY
OF REACHING MINOR FLOOD STAGE.
SARMENT
MTR WATCHES/WARNINGS/ADVISORIES
CA...FLOOD WATCH THROUGH THIS EVENING FOR CAZ006-502>506-508>510-
512>515-529.
PZ...SMALL CRAFT ADVISORY UNTIL 3 AM PST MONDAY FOR PIGEON PT TO PT
PINOS 0-10 NM-SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 9 AM TO 3 PM PST MONDAY FOR MRY BAY-
PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT PIEDRAS
BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 PM PST MONDAY FOR PIGEON PT TO PT
PINOS 10-60 NM-PT ARENA TO PT REYES 0-10 NM-PT ARENA TO PT
REYES 10-60 NM-PT REYES TO PIGEON PT 0-10 NM.
SHORT TERM...KENNEDY
LONG TERM....KENNEDY
AVIATION...CANEPA
MARINE...SARMENT
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