744
FXUS66 KMTR 310029
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
429 PM PST THU JAN 30 2025
..NEW AVIATION
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 WITH RESPECT TO 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
(00Z TAFS)
ISSUED AT 428 PM PST THU JAN 30 2025
SCATTERED MID-LEVEL CLOUDS 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 WIDESPREAD 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. RAIN
APPROACHES THE MONTEREY BAY AT THE END OF THE TAF PERIOD.
VICINITY OF SFO...VFR WITH SCATTERED LOWER CLOUDS LASTS INTO THE
LATE NIGHT BEFORE MVFR CIGS FILL AROUND THE SF BAY. SOUTHEAST WINDS
BUILD INTO EARLY FRIDAY AS PASSING SHOWERS BEGIN TO ARRIVE. MORE
CONSISTENT RAIN BEGINS TO BUILD IN THE LATE MORNING WITH BREEZY
SOUTHERLY WINDS AND SOME REDUCTION IN VISIBILITIES. SHOWER ACTIVITY
LASTS WELL INTO THE NIGHT.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...SCATTERED LOW CLOUDS WITH MODERATE WEST
WINDS LAST AROUND MONTEREY BAY INTO THE LATE EVENING. THESE WINDS
REDUCE INTO THE NIGHT AS MVFR CIGS BUILD ALONG THE COAST AND MOVE
INLAND, FILLING OVER THE MRY. THESE CIGS ARE EXPECTED TO LAST INTO
THE MID MORNING BEFORE RISING. MVFR CIGS BUILD AGAIN INTO THE
AFTERNOON AS SHOWERS APPROACH THE MONTEREY BAY. MORE CONSISTENT RAIN
ARRIVES SLIGHTLY AFTER THE END OF THE TAF PERIOD.
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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