294
FXUS66 KMTR 302249
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
249 PM PST THU JAN 30 2025
..NEW SYNOPSIS, SHORT TERM, LONG TERM, MARINE
SYNOPSIS
ISSUED AT 248 PM PST THU JAN 30 2025
THE FIRST OF NUMEROUS ROUNDS OF RAINFALL WILL BEGIN LATE TONIGHT
ACROSS THE NORTH BAY AND THEN GRADUALLY SPREADS SOUTH AND INLAND
ACROSS THE REST OF OUR AREA TOMORROW AND SATURDAY. SCATTERED LIGHT
RAIN LINGERS ON SUNDAY OUT AHEAD OF A STRONGER, MORE IMPACTFUL
SYSTEM FOR THE BEGINNING OF NEXT WEEK AND BEYOND.
SHORT TERM
(THIS EVENING THROUGH FRIDAY)
ISSUED AT 248 PM PST THU JAN 30 2025
CLOUD COVER HAS INCREASED TODAY ALONG THE COAST, WITH MOSTLY SUNNY
SKIES INLAND. LIGHT RAIN WILL BEGIN TO MOVE ONSHORE LATE TONIGHT
ACROSS THE NORTH BAY AND GRADUALLY SPREAD SOUTH AND FARTHER INLAND
DURING THE DAY TOMORROW. AS THE INCREASED MOISTURE BUILDS OUT AHEAD
OF THE RAINFALL, EXPECT PATCHY FOG AND DRIZZLE TO INCREASE IN
COVERAGE, ESPECIALLY ALONG THE COAST FROM THE NORTH BAY SOUTH TO THE
SANTA CRUZ COASTAL RANGE. OVERNIGHT LOWS INTO EARLY TOMORROW MORNING
WILL STILL BE ON THE COLD SIDE ACROSS SOUTHERN MONTEREY COUNTY AND
SAN BENITO COUNTY, WHILE CLOUD COVER AND INCREASED MOISTURE WILL
LEAD TO MORE MILD, SEASONAL LOW TEMPERATURES FOR THE REMAINDER OF
OUR FORECAST AREA.
LONG TERM
(FRIDAY NIGHT THROUGH NEXT WEDNESDAY)
ISSUED AT 248 PM PST THU JAN 30 2025
CONFIDENCE CONTINUES TO INCREASE FOR WIDESPREAD IMPACTFUL RAINFALL TO
PERSIST THROUGH THE REMAINDER OF THE EXTENDED FORECAST. THE FIRST
SYSTEM ARRIVES ON OUR DOORSTEP LATE TONIGHT. MUCH OF THE NORTH BAY
WILL HAVE ALREADY SEEN BETWEEN 0.50-1.00" OF RAIN BY LATE TOMORROW
NIGHT AND EARLY SATURDAY. THE FOCUS OF HIGHER RAINFALL AMOUNTS WILL
THEN SHIFT SOUTH INTO THE BAY AREA, EAST BAY AND SANTA CRUZ COASTAL
RANGE THROUGHOUT THE DAY SATURDAY. A RELATIVELY STRONG UPPER LEVEL
TROUGH AXIS WILL SHIFT ONSHORE LATE FRIDAY INTO EARLY SATURDAY WHEN
INCREASED RAINFALL RATES CAN BE EXPECTED FROM THE NORTH BAY INTO THE
BAY AREA. WHILE THE PARENT LOW RECONSOLIDATES WELL TO OUR NORTH,
ZONAL FLOW WITH A SERIES OF EMBEDDED SHORTWAVES WILL CONTINUE TO
DRIVE WIDESPREAD LIGHT RAIN ACROSS MOST OF OUR AREA, WITH ENHANCED
UPSLOPING PRODUCING PERIODS OF MODERATE TO HEAVY RAIN ALONG OUR
COASTAL RANGES THROUGH THE WEEKEND.
THE MAIN UPPER LOW THEN DIVES SOUTH LATE SUNDAY NIGHT INTO MONDAY.
DETERMINISTIC GUIDANCE IS IN DECENT AGREEMENT FOR THE EVOLUTION OF
THE PRIMARY LOW'S SHIFT SOUTH, BUT THIS PART OF THE FORECAST WILL
CONTINUE TO BE WATCHED CLOSELY. ANY CHANGE OR RETREAT NORTH FOR THE
BEGINNING OF NEXT WEEK, WILL RESULT IN BIG CHANGES FOR RAIN TOTALS
OUTSIDE OF THE NORTH BAY.
THE RAINFALL TOTALS FOR TONIGHT THROUGH EARLY MONDAY MORNING SHOULD
ONLY LEAD TO MINOR IMPACTS WRT FLOODING ACROSS THE NORTH BAY.
HOWEVER, BY THE TIME THE SECOND ROUND ARRIVES FOR TUESDAY AND
WEDNESDAY, WE'LL SEE RIVERS AND STREAMS BEGIN TO RESPOND QUICKER TO
THE STEADY FETCH OF RAINFALL EXPECTED. EVEN WITH THE HIGHER END
TOTALS ANTICIPATED, THERE IS ROUGHLY A 10% CHANCE OF FLOODING FOR
NORMAL TROUBLE SPOTS ALONG THE RUSSIAN RIVE IN SONOMA COUNTY AND
OTHER LOCATIONS INTO NAPA COUNTY AND MARIN COUNTY. AS WE MONITOR THE
RAINFALL THIS WEEKEND, AND THE EVOLUTION OF THE LARGER SCALE PATTERN
FOR THE BEGINNING OF NEXT WEEK, KEEP AN EYE ON SUBSEQUENT FORECAST
UPDATES AS THESE RIVER FORECASTS COULD CHANGE CONSIDERABLY. ALONG
WITH THE POTENTIAL FOR PERIODS OF MODERATE TO HEAVY RAIN LEADING TO
FLOODING, THERE WILL ALSO BE MODERATE TO STRONG GUSTY WINDS. THE
STRONGEST WINDS WILL BE ACROSS HIGHER ELEVATIONS, BEGINNING SATURDAY
MORNING WITH THE PASSAGE OF THE AFOREMENTIONED TROUGH AXIS MOVING
ONSHORE. AS SOME MIGHT EXPECT, THE STRONGEST GUSTS SHOULD BE EXPECTED
OVER HIGHER ELEVATIONS LIKE MT HELENA, UP TO 60 MPH AFTER SUNRISE
SATURDAY THROUGH MUCH OF THE DAY. WE'RE ANTICIPATING THE NEED FOR A
WIND ADVISORY BEGINNING AT SOME POINT EARLY SATURDAY, WITH ELEVATED
WIND SPEEDS CONTINUING THROUGH THE MIDDLE OF NEXT WEEK. WHILE STRONG
GUSTY WINDS AT HIGHER ELEVATIONS MAY APPROACH 60 MPH, LOWER LYING
AREAS ALONG THE COAST AND INLAND VALLEYS CAN EXPECT MAX WIND GUSTS
BETWEEN 35-45 MPH AT TIMES.
AVIATION
(18Z TAFS)
ISSUED AT 1159 AM PST THU JAN 30 2025
CLOUD COVER RISES OUR OF MVFR LEVELS INTO THE AFTERNOON FOR THE MORE
INTERIOR SITES BUT LOW CLOUDS LAST THROUGH THE TAF PERIOD ALONG THE
IMMEDIATE COAST. WINDS STAY LIGHT THROUGH THE DAY AND FOR MUCH OF
THE NIGHT BEFORE SOUTHERLY WINDS INCREASE AS THE NEXT STORM SYSTEM
ARRIVES. MVFR CIGS MOVE INLAND AND BECOME WIDES SPREAD INTO THE
NIGHT AS THE SYSTEM NEARS, AND CIGS LAST THROUGH THE REMAINDER FOR
ALL BUT THE MORE SOUTHERN TAF SITES. SHOWERS AND AREA OF MORE
STRATIFORM RAIN ARRIVE IN THE NORTHERN AREAS EARLY FRIDAY MORNING
AND BUILD SOUTH THROUGH THE DAY. RAIN AND MIST WILL REDUCE
VISIBILITIES AS SHOWERS CONTINUE TO BUILD INTO THE AREA.
VICINITY OF SFO...MVFR CIGS LINGER THROUGH THE FIRST HALF OF THE
AFTERNOON BEFORE SCATTERING AND RISING AS MODERATE WEST WINDS BUILD.
VFR LASTS INTO THE NIGHT BEFORE MVFR CIGS FILL AROUND THE SF BAY.
SOUTHEAST WINDS BUILD INTO EARLY FRIDAY AS PASSING SHOWERS BEGIN TO
ARRIVE. MORE CONSISTENT RAIN BEINGS TO BUILD IN THE LATE MORNING
WITH BREEZY SOUTHERLY WINDS AND SOME REDUCTION IN VISIBILITIES.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...MVFR CIGS LINGER INTO THE AFTERNOON BEFORE
RISING ABOVE MVFR LEVELS AS MODERATE WEST WINDS BUILD. THESE WINDS
REDUCE INTO THE EVENING, MVFR CIGS BUILD ALONG THE COAST AND MOVE
INLAND, FILLING OVER THE MRY. THESE CIGS ARE EXPECTED TO LAST INTO
THE MID MORNING.
MARINE
(TONIGHT THROUGH NEXT TUESDAY)
ISSUED AT 248 PM PST THU JAN 30 2025
STRONG SOUTHERLY WINDS WITH GALE FORCE GUSTS BEGIN FRIDAY AND
PERSIST THROUGH TUESDAY. SIGNIFICANT WAVE HEIGHTS WILL REMAIN
MODERATE TO ROUGH. WIDESPREAD RAINFALL IS EXPECTED FRIDAY THROUGH
THURSDAY.
MTR WATCHES/WARNINGS/ADVISORIES
CA...NONE.
PZ...SMALL CRAFT ADVISORY FROM 3 AM TO 9 PM PST FRIDAY FOR PT ARENA
TO PT REYES 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 AM FRIDAY TO 3 AM PST SATURDAY FOR
PT REYES TO PIGEON PT 0-10 NM.
SMALL CRAFT ADVISORY FROM 3 PM FRIDAY TO 3 AM PST SATURDAY FOR
PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT PIEDRAS
BLANCAS 0-10 NM.
SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 9 PM PST FRIDAY
FOR PT ARENA TO PT REYES 10-60 NM.
SMALL CRAFT ADVISORY FROM 9 AM TO 9 PM PST FRIDAY FOR PIGEON PT
TO PT PINOS 10-60 NM.
SHORT TERM...JM
LONG TERM....JM
AVIATION...MURDOCK
MARINE...SARMENT
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