433
FXUS66 KMTR 012302
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
302 PM PST SAT FEB 1 2025
..NEW SHORT TERM, LONG TERM
SYNOPSIS
ISSUED AT 317 AM PST SAT FEB 1 2025
IMPACTFUL ATMOSPHERIC RIVER CONTINUES ACROSS NORTHERN AND CENTRAL
CALIFORNIA. A FLOOD WATCH IS IN EFFECT FOR THE BAY AREA UNTIL 10
PM SUNDAY EVENING. SCATTERED SHOWERS WILL INCREASE IN INTENSITY BY
LATE MORNING BEFORE LIGHTENING OVERNIGHT. LIGHT SHOWERS WILL
CONTINUE ON SUNDAY BEFORE ANOTHER ROUND OF IMPACTFUL RAINFALL
BEGINS MONDAY AND TUESDAY ACROSS THE BAY AREA AND CENTRAL COAST.
SHORT TERM
ISSUED AT 144 PM PST SAT FEB 1 2025
(THIS EVENING THROUGH SUNDAY)
CURRENT SITUATION - A PLUME OF HIGH PWAT (200 PON) MOISTURE
CONTINUES TO TAKE AIM AT CA WITH THE FOCUS OVER THE BAY AREA AND
NORTHWARD. THIS MOISTURE PLUME IS PRETTY RICH AS IT EXTENDS ALL
THE WAY BACK TO HAWAII. THE MOISTURE PLUME IS BEING ENHANCED BY A
NARROW CORRIDOR OF STRONGER WINDS 7-9KT FEET ALOFT. RECENT KMUX
RADAR HAS SHOWN AN UPTICK IN PRECIP OVER SONOMA/MARIN OVER THE
LAST HOUR OR TWO. AS SUCH, RAIN AMOUNTS HAVE ALSO GONE UP WITH
HOURLY RATES 0.25-0.5 INCHES OVER SONOMA. THAT NOW PUSHES RAIN
TOTALS SINCE THIS MORNING 0.5-2.0 INCHES FOR THE NORTH BAY WITH
MUCH LESS SOUTH OF THE GOLDEN GATE.
TONIGHT AND SUNDAY: LIGHT TO MODERATE RAIN WILL BE POSSIBLE EARLY
THIS EVENING UNTIL THE UPPER LEVEL SUPPORT (JET WINDS) DRIFTS
NORTHWARD. ONCE THE JET AND PWAT PLUME DRIFT NORTH PRECIP WILL
TRANSITION TO MORE SHOWERS. EVEN THOUGH THE HIGHEST PWAT PLUME
DRIFTS NORTH IT DOESN'T MEAN THE REST OF TONIGHT AND SUNDAY WILL
BE COMPLETELY DRY. WILL STILL HOLD ONTO SHOWERS THROUGH THE REST
OF THE WEEKEND WITH THE HIGHEST LIKELIHOOD FOR SHOWER ACTIVITY
OVER THE NORTH BAY. BEST WAY TO DESCRIBE SUNDAY WILL BE A LULL IN
PRECIP BEFORE THE NEXT AR ARRIVES EARLY NEXT WEEK.
NO CHANGE WITH ONGOING FLOOD WATCH - RAIN TOTALS ARE PILING UP
AND STREAMS ARE SHOWING SOME RESPONSE, BUT STILL THINKING BEST
CHANCE FOR FLOODING WILL BE AS SUBSEQUENT ARS BRING MORE PRECIP.
THE WEEKEND RAIN IS BASICALLY PRIMING THE "PUMP". THAT BEING SAID,
WILL BE KEEPING A CLOSE EYE ON FLASHIER CREEKS LIKE GREEN VALLEY
CREEK AND MARK WEST CREEK.
OUTSIDE OF PRECIP WINDS HAVE ALSO INCREASED THIS AFTERNOON WITH
GUSTS OF 40-55 MPH ALONG THE COAST. MORE ISOLATED THAN WIDESPREAD,
BUT WINDY NONETHELESS. THE STRONGER WINDS COULD BRING A TREE OR
TWO DOWN OR BLOW AROUND UNSECURED ITEMS. THE GUSTY WINDS WILL
PERSIST THROUGH SUNDAY EVENING. STRONGEST WINDS WILL BE OVER THE
HIGHER TERRAIN, COAST, AND NORTH BAY.
LONG TERM
ISSUED AT 258 PM PST SAT FEB 1 2025
(SUNDAY NIGHT THROUGH NEXT FRIDAY)
LONG TERM FORECAST CAN BE SUMMARIZED IN ONE WORD - WET. THE
MOIST ZONAL FLOW FROM THE WEEKEND WILL BECOME MORE MERIDIONAL AS A
TROUGH DIGS/DEEPENS OFF THE NORCAL/OR COAST. THE FIRST PART OF
MONDAY WILL BEGIN MUCH IN THE SAME WAY SUNDAY ENDED - SHOWERS. AS
THE TROUGH DEEPENS OFF THE COAST THE ASSOCIATED SURFACE LOW WILL
HELP DRAG A COLD FRONT INTO THE BAY AREA. THIS FRONT WILL HELP TAP
INTO THE NEXT MOISTURE PLUME (HIGHER IWV AND IVT VALUES FROM AR
MODEL GUIDANCE). AS SUCH, RAIN WILL RE-INTENSIFY INITIALLY OVER
THE NORTH BAY MONDAY AFTERNOON/EVENING BEFORE SLIDING SOUTH AND
EAST MONDAY NIGHT/EARLY TUESDAY. THIS SECOND ROUND OF PRECIP WILL
BE MORE WIDESPREAD AND HEAVIER THAN THE WEEKEND RAIN. IMPACTS TO
THE TUESDAY MORNING COMMUTE SEEM LIKELY. GIVEN THE HEAVIER RAIN
AND ALREADY PRIMED SOILS/CREEKS/STREAMS CHANCES FOR FLOODING WILL
GO UP TUESDAY, ESPECIALLY THE NORTH BAY. HEAVIER RAIN WILL
TRANSITION TO SHOWERS WITH THE FROPA BY TUESDAY NIGHT. RAINFALL
AMOUNTS WITH SYSTEM TWO WILL BE 2-5" N BAY AND COASTAL MTS,
1-2.5" REST OF BAY AREA AND 1-2" INTERIOR CENTRAL COAST.
WEDNESDAY WILL BE ANOTHER LULL PRECIP KINDA DAY WITH LINGERING
SHOWERS. WEDNESDAY NIGHT INTO THURSDAY WILL BE ANOTHER ROUND OF
HEAVY RAIN AS ANOTHER LOW DEVELOPS OFF THE COAST AND DRAGS ANOTHER
FRONT THROUGH THE REGION. THIS SYSTEM WILL BE COLDER THAN THE
PREVIOUS SYSTEM DROPPING SNOW LEVELS ON THE BACKSIDE WED INTO
THURSDAY AND MORE SO THURSDAY INTO FRIDAY WITH ADDITIONAL SHOTS OF
COLD AIR ADVECTION ALOFT. WHILE COLDER, THE WEDNESDAY TO FRIDAY
SYSTEM DOESN'T APPEAR TO BE AS JUICY LIMITING RAINFALL TOTALS
0.25-1.5". HOWEVER, GIVEN THIS IS THE THIRD SYSTEM IMPACTS COULD
BE HIGHER GIVEN HIGHER CREEKS/STREAMS/RIVERS WILL RESPOND QUICKER
WITH FLOODING CONCERNS. COULD ALSO SEE SOME WET NOVELTY FLAKES
OVER SOME OF THE FOOTHILLS BY FRIDAY. NOT EXPECTING MUCH IN THE
WAY OF SNOW ACCUMULATION, BUT SOME OF THE HIGHEST PEAKS AROUND THE
REGION COULD SEE WET SLUSHY SNOW FROM WEDNESDAY-FRIDAY.
IT SHOULD BE NOTED THAT GIVEN THE ACTIVE PATTERN WITH SEVERAL
ROUNDS OF RAINFALL WPC HAS A GOOD PORTION OF THE AREA UNDER A
MARGINAL TO SLIGHT CHANCE OF EXCESSIVE RAINFALL TODAY THROUGH
WEDNESDAY.
GIVEN THE COLDER AIRMASS OVERNIGHT LOWS WILL START TO BECOME A
PROBLEM LATE IN THE WEEK AND NEXT WEEKEND, ESPECIALLY THOSE
WITHOUT ADEQUATE SHELTER. LOWS IN THE 30S WITH DAMP CONDITIONS
WILL BE PROBLEMATIC.
AVIATION
(18Z TAFS)
ISSUED AT 1030 AM PST SAT FEB 1 2025
OFF AND ON LIGHT TO MODERATE RAINFALL CAN BE EXPECTED TO PERSIST
THROUGH THE FORECAST PERIOD JUST SOUTH OF A MEANDERING STATIONARY
FRONT IN VICINITY OF THE NORTH BAY. OCCASIONALLY GUSTY SOUTHERLY
ORIENTED WINDS WILL CONTINUE THROUGH THE FORECAST PERIOD FOR ALL
TERMINALS.
VICINITY OF SFO...MVFR CIGS ARE EXPECTED TO PREVAIL, WITH OCCASIONAL
LIGHT RAIN. GUSTY SOUTH ORIENTED WINDS WILL PERSIST THROUGH THE
FORECAST PERIOD.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...CIGS WILL HOVER BETWEEN MVFR AND VFR WITH
OCCASIONAL LIGHT RAIN THROUGH THE FORECAST PERIOD WITH
OCCASIONALLY GUSTY SOUTHERLY ORIENTED WINDS THIS AFTERNOON, EASING
THIS EVENING THROUGH SUNDAY MORNING.
MARINE
(TODAY THROUGH THURSDAY)
ISSUED AT 1030 AM PST SAT FEB 1 2025
EXPECT OCCASIONALLY GUSTY SOUTH TO SOUTHWEST WINDS OVER THE OUTER
AND INNER CENTRAL WATER THROUGH MOST OF THE DAY MONDAY BEFORE
WINDS SHIFT NORTHWEST BEHIND A COLD THAT PASSES THROUGH OUR AREA
MONDAY NIGHT INTO TUESDAY. THE GUSTY WINDS WILL PRODUCE FRESH
SWELLS WITH STEEP WIND WAVES.
HYDROLOGY
ISSUED AT 258 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
36% PROBABILITY OF EXCEEDING ACTION/MONITOR STAGE AND A 32%
PROBABILITY OF EXCEEDING MINOR FLOOD STAGE. SHEC1 - NAPA NEAR SAINT
HELENA HAS A 23% PROBABILITY OF EXCEEDING ACTION/MONITOR STAGE AND A
5% PROBABILITY OF EXCEEDING MINOR FLOOD STAGE. APCC1 - NAPA NEAR
NAPA HAS A 25% PROBABILITY OF EXCEEDING ACTION/MONITOR STAGE AND A
16% 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 98% PROBABILITY OF REACHING ACTION/MONITOR STAGE AND A
68% 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 70% PROBABILITY OF REACHING
MINOR FLOOD STAGE, AND GEYC1 - RUSSIAN RIVER AT GEYSERVILLE HAS A
39% PROBABILITY OF REACHING ACTION/MONITOR STAGE AND A 32%
PROBABILITY OF REACHING MINOR FLOOD STAGE.
KR
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 MONDAY FOR PT REYES TO
PIGEON PT 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 3 PM PST SUNDAY FOR PIGEON PT TO PT
PINOS 0-10 NM-PIGEON PT TO PT PINOS 10-60 NM.
SMALL CRAFT ADVISORY UNTIL 3 PM PST THIS AFTERNOON FOR PT PINOS
TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...JM
MARINE...JM
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