812
FXUS66 KMTR 202216
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
216 PM PST WED NOV 20 2024
..NEW SYNOPSIS, SHORT TERM, LONG TERM
SYNOPSIS
ISSUED AT 214 PM PST WED NOV 20 2024
A STRONG ATMOSPHERIC RIVER HAS ARRIVED IN THE NORTH BAY AND WILL
BRING SIGNIFICANT IMPACTS TO THE REGION OVER THE NEXT SEVERAL DAYS
BRINGING CHANCES FOR HEAVY RAINFALL AND STRONG WINDS.
SHORT TERM
(THIS EVENING THROUGH THURSDAY)
ISSUED AT 214 PM PST WED NOV 20 2024
KEY MESSAGES:
-FLOOD WATCH IS EFFECT FOR THE NORTH BAY THROUGH SATURDAY MORNING
-5-12" OF RAINFALL IN THE NORTH BAY THROUGH TUES
-1-6" OF RAINFALL SOUTH OF THE GOLDEN GATE, WITH THE HEAVIEST RAIN
EXPECTED ON FRIDAY
-WIND ADVISORY IN EFFECT FOR THE NORTH BAY, SAN FRANCISCO BAYSHORE,
AND PACIFIC COAST THROUGH EARLY THU FOR GUSTS UP TO 45-50 MPH
-A HIGH SURF ADVISORY IS IN EFFECT THROUGH FRIDAY MORNING FOR
BREAKING WAVES OF 14-22 FT.
-BEACH HAZARD STATEMENT IN EFFECT THROUGH LATE THURSDAY NIGHT.
THE WELL ANTICIPATED "BOMB CYCLONE" CONTINUES TO SIT OFF THE COAST
TO THE NORTH. RADAR AND SATELLITE SHOWS A PROMINENT BAND OF
SUBTROPICAL MOISTURE FLOWING THROUGH THE BAY AREA, ESPECIALLY NORTH
OF THE SANTA CRUZ MOUNTAINS. OBSERVATIONS SHOW THAT MOST OF THE
RAINFALL WITHIN THE LAST 12 HOURS ARE WITHIN THE NORTH BAY WITH
TOTALS RANGING FROM 0.6 TO 2 INCHES, WITH HIGHER TERRAIN SEEING UP
TO 4-5 INCHES! THE LATEST MODEL RUNS AND GUIDANCE CONTINUES TO SHOW
AGREEMENT OF AN UPTICK IN INTENSITY BRINGING HEAVIER RAIN BANDS
GOING INTO THE LATE AFTERNOON AND EARLY EVENING. IN ADDITION, IVT
VALUES CONTINUE TO SHOW SUPPORT OF AN ATMOSPHERIC RIVER EVENT AT
LEAST THROUGH THURSDAY.
EXPECT ANOTHER 1-4 INCHES OF RAIN IN THE BAY AREA, WITH NORTH BAY
SEEING THE HIGHER RAINFALL VALUES GOING INTO THURSDAY. WITH THE
EXPECTED CONTINUOUS RAIN AND THE FRONT BECOMING SEMI-STATIONARY,
FLOOD ADVISORIES HAVE BEEN ISSUED FOR PARTS OF THE NORTH BAY (MOSTLY
SONOMA COUNTY), WITH A POSSIBILITY OF ADDITIONAL PRODUCTS OR
EXTENSIONS BEING ISSUED AS WE CONTINUE TO GET REPORTS OF FLOODING IN
SMALL STREAMS, CREEKS, AND POOR DRAINAGE AREAS.
IN ADDITION, STRONG SOUTHERLY WINDS ARE WELL UNDERWAY WITH THIS
FRONT. MOST OF THE MOUNTAIN RANGES ARE REPORTING STRONG GUSTY WINDS
WITH SEVERAL PLACES SEEING UP TO 55-65 MPH WITH EXPECTATIONS THAT
WINDS WILL CONTINUE TO INCREASE OR REMAIN STRONG AS WE APPROACH THE
LATE AFTERNOON AND EVENING. AS THE FRONT CONTINUES TO BRING HEAVY
RAINFALL AND STRONG SURFACE WINDS, THERE IS A RISK FOR DOWNED TREES
AND BRANCHES, PONDING AND DEBRIS ON ROADWAYS, AND POWER OUTAGES.
THEREFORE, WIND ADVISORY WILL REMAIN IN AFFECT FOR NORTH BAY, SAN
FRANCISCO BAY SHORELINE, AND SAN FRANSICO THROUGH EARLY THURSDAY
EVENING.
LONG TERM
(THURSDAY NIGHT THROUGH NEXT TUESDAY)
ISSUED AT 214 PM PST WED NOV 20 2024
AFTER THURSDAY, THE PARENT LOW THAT SITS OFF OF BRITISH COLUMBIA
WILL LIFT NORTHWARD MAKING ROOM FOR ANOTHER LOW PRESSURE SYSTEM TO
DOMINATE. CLUSTER ANALYSIS SHOWS AGREEMENT THAT THE LOW HAS A GOOD
CHANCE TO MOVING INLAND. THIS SYSTEM WILL KEEP US IN AN ACTIVE
PATTERN THROUGH TUESDAY, BRINGING ADDITIONAL RAINFALL TO THE BAY
AREA, WITH MOST OF THE IMPACT CONTINUING OVER THE NORTH BAY.
RAINFALL THIS WEEKEND WILL TRANSITION FROM A CONTINUOUS PATTERN TO A
MORE OCCASIONAL SHOWER WITH WINDS SLOWLY DIMINISH FRIDAY. SOME
HIGHER TERRAINS, COASTAL AREAS, AND SOME ISOLATED SPOTS MAY BECOMING
GUSTY UP TO 40-50 MPH ON FRIDAY BUT WINDS WILL CONTINUE TO DECREASE
GOING INTO THE WEEKEND. WITH THE MIX OF SUBTROPICAL MOISTURE AND THE
COLD FRONT, THERE WILL BE A INCREASE IN INSTABILITY IN THE
ATMOSPHERE, MAKING WAY FOR CHANCES OF THUNDERSTORM LATE FRIDAY INTO
SATURDAY. IN ADDITION, THERE IS A CONTINUED RISK FOR FLOODING AS WE
CONTINUE TO EXPECT RAIN THROUGH TUESDAY, WHICH WILL PROMOTE
SATURATION OF SOIL AND OVERFLOW OF CREEKS AND STREAMS.
AVIATION
(18Z TAFS)
ISSUED AT 1006 AM PST WED NOV 20 2024
SATELLITE SHOWS LOW STRATUS ENCOMPASSING MOST OF THE AREA
CREATING A MIX OF IFR, MVFR, AND VFR CONDITIONS. WITH THE PASSING
RAIN BANDS MOVING OVER THE NORTH BAY TERMINALS, VISIBILITY HAS
REDUCED, SPECIFICALLY OVER KSTS WHERE IFR CONDITIONS WILL PERSIST
THROUGH THE TAF PERIOD. AS HEAVIER RAIN BANDS MOVE OVER THE
REMAINING TERMINALS IN THE AFTERNOON/EVENING OVER THE SF BAY AND
NORTH BAY, EXPECT VISIBILITY TO REDUCE AND CEILINGS TO LOWER AS
WELL, BUT THEY ARE NOT EXPECTED TO REDUCE BELOW MVFR CONDITIONS.
CURRENTLY MODERATE TO BREEZY AND GUSTY SOUTHERLY WINDS, WITH HIGH
CONFIDENCE WINDS WILL REMAIN PRETTY BREEZY/STRONG AND GUSTY THROUGH
MOST OF THE TAF PERIOD, WITH THE EXCEPTION OF MONTEREY BAY
TERMINALS.
VICINITY OF SFO...VFR WITH STRONG SOUTHERLY WINDS AND SOME SHOWERS
OVER THE TERMINAL. WINDS ARE EXPECTED TO GUST UP TO 40 THIS
AFTERNOON WITH AWW CRITERIA CONTINUING UNTIL 06Z, BUT WINDS WILL
REMAIN GUSTY AFTERWARDS. MVFR CONDITIONS BEGIN THIS AFTERNOON AS THE
RAIN CONTINUES TO BECOME HEAVIER. MVFR CIGS ARE EXPECTED TO CONTINUE
THROUGH THE REMAINDER OF THE TAF PERIOD BUT MODELS DO SHOW MOMENTS
OF VFR FROM 06Z TO 12Z TONIGHT. WITH LOW CONFIDENCE, VFR WAS LEFT
OUT OF THE TAFS FOR THAT TIME FRAME. THERE IS SOME UNCERTAINTY WHEN
RAIN WILL EASE, ESPECIALLY AT THE END OF THE TAF PERIOD, BUT EXPECT
AFTER 18Z.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR THROUGH THE TAF PERIOD, AS THE STORM IS
EXPECTED TO REMAIN FURTHER NORTH. THERE STILL IS A CHANCE FROM SOME
VCSH, BUT IMPACTS TO CIGS AND VIS REMAINS UNLIKELY. SOUTHERLY WINDS
ARE EXPECTED TO BUILD TO BREEZY WITH A CHANCE OF GUSTY WINDS OVER
KMRY BY THE AFTERNOON.
MARINE
(TODAY THROUGH MONDAY)
ISSUED AT 1006 AM PST WED NOV 20 2024
A HURRICANE FORCE STORM HAS MOVED OFF THE COAST OF WASHINGTON AND
WILL SLOWLY WEAKEN THROUGH THE REST OF THE WEEK BUT STRONG GALES
CONDITIONS WILL CONTINUE IN THE NORTHERN WATERS. VERY ROUGH SEAS
UP TO 20 FEET IN THE NORTHERN ZONES ARE PROPAGATING SOUTH THROUGH
THE COASTAL WATERS. THESE WILL BEGIN TO ABATE THURSDAY AND
CONTINUE ON THAT TREND THROUGH THE WEEKEND. DESPITE THE GRADUAL
IMPROVEMENT, CONDITIONS WILL REMAIN INCREDIBLY DANGEROUS TO ALL
BUT THE LARGEST VESSELS OVER THE NEXT 48 HOURS.
MTR WATCHES/WARNINGS/ADVISORIES
CA...WIND ADVISORY UNTIL 6 AM PST THURSDAY FOR CAZ006-502>506-508-509.
HIGH SURF ADVISORY UNTIL 6 AM PST FRIDAY FOR CAZ006-505-509-530.
FLOOD WATCH THROUGH LATE FRIDAY NIGHT FOR CAZ502>506.
BEACH HAZARDS STATEMENT THROUGH LATE THURSDAY NIGHT FOR CAZ529.
PZ...GALE WARNING UNTIL 3 PM PST THIS AFTERNOON FOR SF BAY N OF BAY
BRIDGE.
SMALL CRAFT ADVISORY UNTIL 3 AM PST THURSDAY FOR MRY BAY.
GALE WARNING UNTIL 9 AM PST THURSDAY FOR PT ARENA TO PT REYES 0-
10 NM.
GALE WARNING UNTIL 3 AM PST THURSDAY FOR PIGEON PT TO PT PINOS 0-
10 NM-PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES
10-60 NM-PT REYES TO PIGEON PT 0-10 NM.
SMALL CRAFT ADVISORY UNTIL 9 PM PST THURSDAY FOR PT PINOS TO PT
PIEDRAS BLANCAS 0-10 NM.
SHORT TERM...SO
LONG TERM....SO
AVIATION...SO
MARINE...SO
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