169
FXUS66 KMTR 042354
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
354 PM PST TUE FEB 4 2025
..NEW AVIATION
SYNOPSIS
ISSUED AT 1202 AM PST TUE FEB 4 2025
AN ATMOSPHERIC RIVER WILL CONTINUE TO BRING HEAVY RAIN, URBAN AND
RIVER FLOODING, AND STRONG WINDS TO THE BAY AREA AND CENTRAL
COAST THROUGH TUESDAY. THERE IS ALSO AN INCREASING CHANCE FOR
THUNDERSTORMS IN THE AFTERNOON. WHILE LESS IMPACTFUL IN THE
SECOND HALF OF THE WEEK, RAIN CHANCES CONTINUE THROUGH FRIDAY.
SHORT TERM
ISSUED AT 215 PM PST TUE FEB 4 2025
(THIS EVENING THROUGH WEDNESDAY)
KEY POINTS:
* FLOOD ADVISORIES AND FLOOD WARNINGS CONTINUES FOR PORTIONS OF
THE BAY AREA
* FLOOD WATCH REMAINS EFFECT THROUGH 4 AM WEDNESDAY ACROSS THE
BAY AREA AND CENTRAL COAST
* DYNAMIC AFTERNOON/EVENING AS A COLD FRONT BRINGS HEAVY RAIN,
VERY GUSTY WINDS, AND POSSIBLE THUNDERSTORMS
* POST FRONTAL COLD TEMPERATURES TONIGHT- N BAY VALLEY FROST
ADVISORY
* THUR-FRI AR WILL BRING ANOTHER ROUND OF RAIN WITH RE-NEWED
FLOODING CONCERNS
* COLD MORNING TEMPERATURES RETURN MID-WEEK BUT TEMPERATURES
WILL DROP MORE SIGNIFICANTLY OVER THE WEEKEND
AFTERNOON/EVENING - THE MUCH ANTICIPATED SURFACE LOW, ASSOCIATED
COLD FRONT, AND ACCOMPANYING UPPER LEVEL JET MAX ARE MAKING THEIR
PRESENCE KNOWN. SINCE THIS MORNING, RADAR HAS BECOME MUCH MORE
ACTIVE WITH A LINE INTERMIXED WITH CELLS SHOWING UP ALONG THE
APPROACHING COLD FRONT. THE WIND FIELD AHEAD OF THE FRONT HAS ALSO
RAMPED UP WITH A FEW COASTAL SITES SHOWING GUSTS 65-85 MPH. A
SPECIAL BALLOON SOUNDING WAS LAUNCHED FROM OAK AT 20Z TO FURTHER
ANALYZE THE ATMOSPHERIC PROFILE, ESPECIALLY THE WIND PROFILE. THE
BIGGEST CONCERNS THIS AFTERNOON - LOW CAPE HIGH SHEAR ENVIRONMENT
WILL LEAD TO CONVECTIVELY DRIVEN WIND AND POSSIBLE SPIN UPS WITH
ANY STRONGER CELL. GIVEN THE JUICY ATMOSPHERE, ANY STRONGER CELL
HAS SOME DECENT RAINFALL ASSOCIATED WITH IT - 0.5-0.75" PER HOUR.
THOSE RATES ON ALREADY WET SOIL/FULL CREEKS/STREAMS WILL ADD
ADDITIONAL FLOODING CONCERNS. SIMPLY PUT, MAKE SURE YOU HAVE WAYS
TO RECEIVE WEATHER ALERTS WHETHER IT'S FOR SEVERE OR FLOODING.
ALSO, ALLOW FOR EXTRA TIME DURING THE EVENING AS HEAVY RAIN WILL
IMPACT THE COMMUTE. DO NOT DRIVE THROUGH FLOODED ROADWAYS.
TONIGHT INTO WEDNESDAY: CONDITIONS WILL GRADUALLY IMPROVE AS THE
COLD FRONT PUSHES THROUGH THE FORECAST AREA. CONVECTIVE RAIN FROM
THE EVENING WILL TRANSITION TO SCATTERED SHOWERS N TO S. WHILE
PRECIP GRADUALLY DIMINISHES IN COVERAGE AND INTENSITY FLOODING
CONCERNS WILL REMAIN DUE TO FULL CREEKS/STREAMS. WINDS WILL ALSO
DECREASE BEHIND THE FRONT. SOME CHILLY AIR IS EXPECTED TO FILL IN
BEHIND THE FRONT WITH DECREASING WINDS AND CLEARING SKIES. AS
SUCH, A FROST ADVISORY HAS BEEN ISSUED TO CAPTURE TEMPERATURES
REACHING THE LOW TO MID 30S FOR THE SONOMA VALLEY SPECIFICALLY.
EVEN IF THE CLOUDS LINGER LONGER AND TEMPERATURES REMAIN IN THE
MID TO UPPER 30S IT WILL FEEL COLD GIVEN THE DAMP CONDITIONS.
WEDNESDAY WILL BE A REPRIEVE AS ONE SYSTEM EXITS AND ANOTHER
APPROACHES FROM THE WEST. GIVEN THE COLDER AIR ALOFT AND UPSTREAM
UPPER LEVEL TROUGH WIDELY SCATTERED SHOWERS WILL BE POSSIBLE.
LONG TERM
ISSUED AT 245 PM PST TUE FEB 4 2025
(WEDNESDAY NIGHT THROUGH NEXT MONDAY)
WEDNESDAY NIGHT WILL BE A LOW CONFIDENCE HIGHER IMPACT POTENTIAL
FORECAST. A LOT WILL DEPEND UP CLOUD COVER AND IMPACTS FOR
OVERNIGHT LOWS. FOR NOW, CURRENT FORECAST IS TRENDING COLDER WITH
WIDESPREAD 30S TO NEAR 40 AND INTERIOR CENTRAL COAST NEAR
FREEZING. A FROST ADVISORY MAY BEE NEEDED.
THURSDAY AND FRIDAY...ANOTHER AR IS STILL ON TRACK WITH MORE
MOISTURE TAKING AIM AT THE REGION. THANKFULLY THIS AR LOOKS MUCH
WEAKER WITH LESS OF A DEEP MOISTURE TAP. EXPECT SHOWER COVERAGE TO
INCREASE THROUGH THE DAY ON THURSDAY AND LINGER INTO FRIDAY.
DESPITE A WEAKER SYSTEM FLOODING CONCERNS WILL REMAIN GIVEN HOW
MUCH RAIN HAS FALLEN OVER THE LAST 24 HOURS. RAINFALL AMOUNTS ARE
GENERALLY EXPECTED TO BE 0.25-1.00" AND 1.5" COASTAL MTS. AS
PRECIP BEGINS TO TAPER OFF ON FRIDAY COLDER AIR BEGINS TO MOVE IN
FROM THE NORTH LOWERING SNOW LEVELS. SOME WET SNOW WILL BE
POSSIBLE OVER THE HIGHER TERRAIN.
DRIER WEATHER FINALLY RETURNS OVER THE WEEKEND. THE WEATHER
IMPACTS QUICKLY TURNS TOWARD COLD OVERNIGHT LOWS. WE'RE TALKING
WIDESPREAD 30S WITH INTERIOR IN THE MID TO UPPER 20S. FROST AND
FREEZE PRODUCTS WILL LIKELY BE NEEDED.
AVIATION
(00Z TAFS)
ISSUED AT 353 PM PST TUE FEB 4 2025
MAIN FRONTAL BAND IS CURRENTLY NEAR THE GOLDEN GATE AND WILL
QUICKLY SHIFT SOUTHWARD OVER THE NEXT SEVERAL HOURS. HEAVY RAIN,
LOW CIGS AND VERY STRONG SOUTHERLY WINDS CONTINUE AHEAD OF THE
FRONTAL PASSAGE WITH A GENERAL WIND SHIFT TIME OF 01-02Z FOR THE
BAY AREA TERMINALS. WIND SHIFT WILL BE SLIGHTLY LATER FOR SAN JOSE
AND CENTRAL COAST TERMINALS AS THE BOUNDARY SHIFTS SOUTH OF THE
AREA BY 06Z.
VICINITY OF SFO...AIRPORT WEATHER WARNING ISSUED FOR WIND GUSTS
IN EXCESS OF 35K THRU 05Z. SOUTHEAST WINDS WILL TURN WESTERLY
BETWEEN 01-02Z WITH RAIN QUICKLY ENDING BEHIND THE FRONTAL
PASSAGE. VFR SKIES FORECAST OVERNIGHT BEHIND THE FRONT WITH
FORECAST FOR WEDS SHOWING VFR SKIES AND GENERALLY LIGHT WINDS.
SFO BRIDGE APPROACH... SIMILAR TO SFO.
MONTEREY BAY TERMINALS...INCREASING RAIN, SOUTHEAST WINDS AND
LOWERING CIGS THRU EARLY EVENING. WIND SHIFT FROM SE TO WESTERLY
FORECAST TO OCCUR BETWEEN 03-04Z THIS EVENING WITH RAIN ENDING
BEHIND THE FRONT. LIGHTER WINDS AND VFR CONDITIONS FORECAST
OVERNIGHT INTO WEDS MORNING.
MARINE
(TONIGHT THROUGH NEXT SUNDAY)
ISSUED AT 115 PM PST TUE FEB 4 2025
WINDS HAVE SHIFTED TO THE NORTHWEST FOR AREAS NORTH OF POINT
REYES. GALE FORCE WINDS CONTINUE SOUTH OF POINT REYES WITH STORM
FORCE WINDS ALONG THE INNER WATERS FROM PIGEON POINT TO POINT
PIEDRAS BLANCAS. PERIODS OF RAIN WITH THUNDERSTORM CHANCES
INCREASE OVER THE COASTAL WATERS THROUGHOUT THE DAY WITH THE
HIGHEST LIKELIHOOD OVER THE SOUTHERN WATERS. EXPECT BUILDING
SIGNIFICANT WAVE HEIGHTS WITH FRESH SWELLS AND STEEP WIND WAVES
RESULTING IN HAZARDOUS MARINE CONDITIONS. ANOTHER STORM WILL
IMPACT THE COASTAL WATERS THURSDAY INTO FRIDAY WITH INCREASING
WINDS AND RAIN.
HYDROLOGY
ISSUED AT 1200 PM PST TUE FEB 4 2025
A MOISTURE RICH ATMOSPHERIC RIVER AND ACCOMPANYING SURFACE LOW IS
BRINGING WIDESPREAD RAINFALL ACROSS THE BAY AREA AND CENTRAL
COAST. ALREADY PRIMED SOILS AND HIGHER RAIN RATES WILL MAINTAIN
AN INCREASED POTENTIAL FOR FLOODING ACROSS THE NORTH BAY AND
COASTAL RANGES TODAY INTO WEDNESDAY. CNRFC HAS INCREASED
FORECASTED RIVER STAGES ACROSS SEVERAL RIVERS AND STREAMS IN
RESPONSE TO HIGHER FORECASTED PRECIPITATION. THE LATEST MAIN STEM
RIVER FORECAST HAS THE RUSSIAN RIVER AT JOHNSONS BEACH AT
GUERNVILLE (GUEC1) RISING TO ACTION STAGE (29 FT) THIS EVENING AND
INTO MINOR FLOOD STAGE (32 FT) OVERNIGHT. A FLOOD WARNING IS IN
EFFECT FOR THIS LOCATION BEGINNING AT 1 AM TONIGHT. IN NAPA COUNTY
THE NAPA RIVER AT ST HELENA IS FORECAST TO RISE INTO ACTION STAGE
(16 FT) THIS AFTERNOON AND THE NAPA RIVER NEAR NAPA IS FORECAST
TO RISE INTO ACTION STAGE (22 FT) TONIGHT.
OTHER NON-MAIN STEM FORECAST POINTS THAT ARE CURRENTLY UNDER A
FLOOD WARNING INCLUDE...
GEYC1 - RUSSIAN RIVER AT GEYSERVILLE IS CURRENTLY IN MINOR FLOOD
(>39.7 FT) AND FORECAST TO REMAIN IN MINOR FLOOD THROUGH TONIGHT.
MWEC1 - MARK WEST CREEK AT MIRABEL HEIGHTS IS CURRENTLY IN MINOR
FLOOD (>55 FT) AND CONTINUING TO RISE. IT IS EXPECTED TO REACH
MODERATE FLOOD (>59 FT) LATER THIS AFTERNOON.
GRQC1 - GREEN VALLEY CREEK AT MARTINELLI ROAD IS CURRENTLY IN
MODERATE FLOOD (>63 FT) AND RISING.
CTIC1- LAGUNA DE SANTA ROSA AT STONY POINT ROAD NEAR COTATI IS
CURRENTLY IN MINOR FLOOD (>84 FT) AND CONTINUING TO RISE. IT IS
EXPECTED TO REACH MODERATE FLOOD (>85 FT) IN THE NEXT FEW HOURS.
THESE LOCATIONS WILL BE HANDLED THROUGH ONGOING FLOOD
ADVISORIES.
A FLOOD WATCH WILL REMAIN IN EFFECT THROUGH LATE TONIGHT.
SEVERAL FLOOD ADVISORIES ARE IN EFFECT THIS AFTERNOON WITH
NUMEROUS REPORTS OF URBAN AND SMALL STREAM FLOODING ACROSS THE
NORTHERN HALF OF THE BAY AREA.
MTR WATCHES/WARNINGS/ADVISORIES
CA...FLOOD WATCH THROUGH LATE TONIGHT FOR CAZ006-502>506-508>510-
512>518-528>530.
FROST ADVISORY FROM 11 PM THIS EVENING TO 9 AM PST WEDNESDAY FOR
CAZ506.
WIND ADVISORY UNTIL 11 PM PST THIS EVENING FOR CAZ508>510-
512>518-528>530.
PZ...GALE WARNING UNTIL 9 PM PST THIS EVENING FOR MRY BAY-PIGEON PT
TO PT PINOS 10-60 NM-PT REYES TO PIGEON PT 0-10 NM-SF BAY N
OF BAY BRIDGE.
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.
STORM WARNING UNTIL 9 PM PST THIS EVENING FOR PIGEON PT TO PT
PINOS 0-10 NM-PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...MM
LONG TERM....MM
AVIATION...RW
MARINE...RW
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