406
FXUS66 KMTR 171702
AFDMTR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN FRANCISCO CA
902 AM PST SUN NOV 17 2024
..NEW UPDATE, MARINE
SYNOPSIS
ISSUED AT 350 AM PST SUN NOV 17 2024
LIGHT RAIN CHANCES THIS AFTERNOON AND EVENING, MAINLY NORTH OF
MONTEREY BAY. QUIET BUT CHILLY MONDAY AND TUESDAY WITH COLD
OVERNIGHT LOWS AGAIN MONDAY NIGHT. A BIT MORE EXCITEMENT FOR THE
LATTER HALF OF THE WEEK WITH THE POTENTIAL FOR IMPACTFUL RAINFALL
IN THE NORTH BAY.
UPDATE
ISSUED AT 856 AM PST SUN NOV 17 2024
KMUX RADAR HAS BEGUN SHOWING FAINT ECHOES OVER MENDOCINO COUNTY
AHEAD OF THE SHOT OF RAIN EXPECTED LATER TODAY. THE NORTH BAY AND
MUCH OF THE BAY AREA ARE ALREADY MOSTLY CLOUDY, WITH INCREASING
CLOUDINESS ACROSS THE SOUTH BAY AND CENTRAL COAST THROUGH THE DAY
AS A COLD FRONT APPROACHES. THE FREEZE WARNINGS AND FROST
ADVISORIES FOR THE INTERIOR CENTRAL COAST WERE ALLOWED TO EXPIRE
EARLIER THIS MORNING, BUT AS PART OF THE NEXT FORECAST UPDATE, THE
OPERATIONS TEAM WILL EVALUATE THE NEED TO ISSUE ANY RENEWED
PRODUCTS FOR TONIGHT THROUGH MONDAY MORNING.
DIALH
SHORT TERM
(TODAY AND TONIGHT)
ISSUED AT 350 AM PST SUN NOV 17 2024
CLEAR SKIES, CALM WINDS, AND ANOTHER CHILLY MORNING TODAY. UPPER AIR
TRENDS THIS MORNING SHOW WEAK SHORTWAVE RIDGING BUILDING OVER THE
REGION TODAY. 500 MB HEIGHT RISES OVER PAST SEVERAL HOURS HAVE
CONTRIBUTED TO A VERY STABLE ATMOSPHERE AND SYNOPTIC SCALE
SUBSIDENCE. THE TREND REVERSES LATER TODAY AS THE NEXT STORM SYSTEM
APPROACHES. HIGH TEMPS TODAY WILL BE NEAR WHAT THEY WERE YESTERDAY,
OR EVEN A DEGREE OR TWO COOLER IN SOME LOCATIONS AS COOL AIR
CONTINUES TO BE ADVECTED IN FROM THE NORTH. THE NEXT SYSTEM
APPROACHES RATHER QUICKLY, AND THE ASSOCIATED SURFACE COLD FRONT IS
EXPECTED TO MOVE THROUGH THE AREA BY THIS AFTERNOON. SOME LIGHT
SCATTERED SHOWERS ARE EXPECTED TO DEVELOP EARLY THIS AFTERNOON ALONG
THE WARM FRONT CURRENTLY DRAPED ALONG THE NORTHERN HALF OF THE WEST
COAST. A FEW HEAVIER SHOWERS WILL DEVELOP AS THE COLD FRONT FINALLY
MOVES THROUGH LATER THIS AFTERNOON IN THE NORTH BAY AND BY THE EARLY
EVENING FOR THE BAY AREA AND POINTS SOUTHWARD. REALLY NOT MUCH RAIN
EXPECTED FROM THIS WEAK SYSTEM BY THE TIME IT MAKES IT INTO OUR
REGION. GENERALLY AROUND 0.10" FOR MOST OF THE NORTH BAY, LOCALLY UP
TO 0.25" IN THE COASTAL RANGES. FOR AREAS FROM THE BAY AREA
SOUTHWARD, 0.10" OR LESS CAN BE EXPECTED, EXCEPT FOR A LUCKY FEW
THAT PICK UP ONE OF THE HEAVIER SHOWERS THIS EVENING AND MAY END UP
WITH 0.20" OR SO. EXPECT CLOUD COVER TO INCREASE AS THE WARM FRONT
APPROACHES THE COAST, REMAINING OVERCAST FOR MOST FOLKS THROUGH THIS
AFTERNOON. CLOUD COVER REMAINS BUT BECOMES MORE SCATTERED OVERNIGHT
BEHIND THE COLD FRONT.
LONG TERM
(MONDAY THROUGH SATURDAY)
ISSUED AT 350 AM PST SUN NOV 17 2024
KEY POINTS IN THE LONG TERM:
-CHILLY BUT QUIET MONDAY AND TUESDAY
-COLD OVERNIGHT MONDAY, TEMPS IN THE 30S/LOWER 40S
-INCREASING CONFIDENCE IN A POTENTIAL AR SYSTEM BEGINNING MID WEEK
MONDAY WILL BE ON THE COOLER SIDE WITH BREEZY NW WINDS CONTINUING
INTO THE EVENING HOURS ALONG THE COAST AND NW-SE ORIENTED VALLEYS
WITH GUSTS TO 20-25 MPH IN THESE AREAS BEFORE MIDNIGHT. AS THE WINDS
SUBSIDE AND SKIES CLEAR, LOW TEMPERATURES FALL INTO THE 30S OR LOWER
40S FOR MOST. TEMPERATURES TUESDAY LARGELY MIRROR MONDAY, EXCEPT
OVERNIGHT LOWS WILL BE A BIT WARMER THANKS TO INCREASING MOIST
SOUTHERLY FLOW AHEAD OF THE NEXT STORM SYSTEM.
SPEAKING OF THE NEXT STORM SYSTEM, QUITE A BIT TO TALK ABOUT. THE
HIGH AMPLITUDE WAVE PATTERN FORMING IN THE NORTHEAST PACIFIC
MENTIONED IN PREVIOUS DISCUSSIONS LOOKS LIKE OUR FIRST REAL THREAT
FOR SOME DEGREE OF HAZARDOUS RAINFALL. A ROBUST 140 KT JET STREAK
DOWNSTREAM OF A VERY POSITIVELY TILTED TROUGH IS PROGGED TO DRAW IN
A STRONG AND PERSISTENT SOURCE OF SUBTROPICAL MOISTURE, AIDED BY A
BRANCH OF THE SUBTROPICAL JET TO THE SOUTH. GIVEN THE LOCATION OF
THE JET MAXIMA AND ORIENTATION OF THE TROUGH, IT'S REASONABLE TO
EXPECT A CORRIDOR OF HIGH RAINFALL TOTALS ACROSS COASTAL NORCAL WITH
A QUICK TAPER TO THE SOUTH. AS OF THIS FORECAST, RAINFALL IS
EXPECTED TO BEGIN IN THE NORTH BAY WEDNESDAY MORNING WITH OFF AND ON
SHOWERS POTENTIALLY LINGERING THROUGH SATURDAY. BY THE WEEKEND, THE
DOWNSTREAM JET FINALLY BEGINS TO WEAKEN AS WE SEE MORE INTERACTION
FROM THE SUBTROPICAL JET TO THE SOUTH. THIS WILL ULTIMATELY AID IN
BREAKING DOWN THE STAGNANT UPPER LOW AND ALLOWING THINGS TO
PROGRESS, BRINGING RAIN CHANCES FURTHER SOUTH THROUGHOUT THE REST OF
THE BAY AREA AND CENTRAL COAST BY SATURDAY. THE BIGGEST CHANGE IN
THINKING WITH THIS FORECAST ISSUANCE IS THE OVERALL CONFIDENCE IN
THIS PATTERN. ENSEMBLE CLUSTER ANALYSIS ADVERTISES GOOD CONFIDENCE
WITH AROUND 30% OF MEMBERS SUPPORTING A PATTERN DRIER THAN THE
ENSEMBLE MEAN. THIS GIVES US ENOUGH CONFIDENCE TO BEGIN MESSAGING
THE POTENTIAL FOR THE FIRST PROPER ATMOSPHERIC RIVER OF THE SEASON.
STILL A BIT TOO EARLY TO START TALKING ABOUT AMOUNTS, AND WE DON'T
REALLY SEE ANYTHING ALARMING THAT HINTS TOWARDS MAJOR FLOODING,
ESPECIALLY SINCE IT'S EARLY IN THE SEASON AND SOILS AND RESERVOIRS
CAN HANDLE SOME PROLONGED HEAVY RAIN. HOWEVER, WE DO HAVE SOME
CONCERN FOR NUISANCE FLOODING IN PORTIONS OF THE NORTH BAY WHERE
THE AR AND RESULTANT HIGHER RAINFALL RATES MAY STALL AND LINGER
THROUGH THE LATTER HALF OF THE WEEK. ALSO IMPORTANT TO KEEP IN
MIND THAT THIS STALLING AXIS OF MOISTURE COULD WOBBLE A FEW TENS
OF MILES TO THE NORTH OR SOUTH, WHICH COULD GREATLY AFFECT HOW
MUCH RAINFALL CERTAIN AREAS RECEIVE. IN FACT, THE AFOREMENTIONED
DISCREPANCY WHERE 30% OF ENSEMBLE MEMBERS DEPICT A DRIER-THAN-THE-
MEAN SCENARIO FOR US ARE MAINLY DUE TO THIS POSSIBILITY THE JET
AXIS SHIFTING SLIGHTLY TO THE NORTH. THE CONFIDENCE IN THIS AR
PATTERN OCCURING IN THE FIRST PLACE IS ACTUALLY MUCH HIGHER...IT'S
JUST THAT THE BIGGEST QUESTION IS HOW MUCH DOES THE JET AXIS
WOBBLE TO THE NORTH DURING THE LATE WEEK.
BE SURE TO PAY CLOSE ATTENTION AND STAY UP TO DATE WITH THE WEATHER
FORECAST OVER THE NEXT FEW DAYS FOR THE LATEST UPDATES AND MOST
ACCURATE INFORMATION.
AVIATION
(12Z TAFS)
ISSUED AT 350 AM PST SUN NOV 17 2024
VFR CONDITIONS PREVAIL EARLY THIS MORNING, BUT WILL DETERIORATE AS
THE DAY PROGRESSES DUE TO A WEAK COLD FRONT PUSHING ACROSS THE
REGION. FIRST UP, THE NORTH BAY WILL SEE LOWERING CEILINGS TO MVFR
AND AT TIMES IFR THAT WILL SPREAD SOUTHWARD THROUGHOUT THE DAY. RAIN
SHOWERS WILL ALSO ACCOMPANY THIS FRONTAL PASSAGE WITH POTENTIAL FOR
LINGERING POST FRONTAL RAIN SHOWERS. ACROSS THE CENTRAL COAST,
SCATTERED SHOWERS BECOME MORE LIKELY LATE THIS AFTERNOON AND INTO
THE EVENING HOURS. BY LATE THIS EVENING, CEILINGS WILL GRADUALLY
START TO RISE WITH MOST SITES RETURNING TO VFR CONDITIONS AS SHOWER
CHANCES DIMINISH.
VICINITY OF SFO...VFR TRANSITIONING TO MVFR BY EARLY THIS AFTERNOON
AS SHOWER CHANCES INCREASE. CEILINGS WILL GRADUALLY LOWER AND BECOME
MVFR WITH CHANCES FOR LIGHT SHOWERS INCREASING AFTER 20/21Z.
SCATTERED SHOWERS WILL PERSIST THROUGH LATE EVENING BEFORE CEILINGS
START TO LIFT AND SHOWER CHANCES DIMINISH (AROUND 05Z MONDAY). AFTER
THE COLD FRONTAL PASSAGE, GUSTY NORTHWEST WINDS WILL RETURN WITH
GUSTS UP TO 23 KNOTS CURRENTLY ANTICIPATED.
SFO BRIDGE APPROACH...SIMILAR TO SFO.
MONTEREY BAY TERMINALS...VFR BECOMING MVFR THIS AFTERNOON. SHOWER
CHANCES INCREASE AFTER 00Z/01Z WITH CEILINGS EXPECTED TO LOWER TO
BORDERLINE MVFR HEIGHTS. CEILINGS WILL LIFT IN WAKE OF THE FRONTAL
PASSAGE AROUND 09Z MONDAY.
MARINE
(TODAY THROUGH FRIDAY)
ISSUED AT 856 AM PST SUN NOV 17 2024
A COLD FRONT WILL SWEEP THROUGH THE COASTAL WATERS ON SUNDAY INTO
MONDAY. THE PASSING COLD FRONT WILL BRING SCATTERED SHOWERS AND
GUSTY NORTHERLY WINDS TO THE REGION. THE GUSTY WINDS WILL RESULT
IN STEEPER WIND WAVES AND LOCALLY HAZARDOUS CONDITIONS. SEAS ARE
EXPECTED TO PEAK BETWEEN 10 TO 15 FEET BEFORE SUBSIDING SLOWLY
DURING THE EARLY WORK WEEK. WINDS WILL REMAIN GUSTY THROUGH
MIDWEEK.
BEACHES
ISSUED AT 856 AM PST SUN NOV 17 2024
KING TIDE SEASON IS HERE AND WILL BRING HIGH TIDES UP TO 1-1.5 FT
ABOVE NORMAL TODAY - MONDAY. THE LATE MORNING TIDE CYCLE WILL BE
THE ONE TO WATCH, ESPECIALLY FOR EXPOSED OCEAN BEACHES WHEN HIGH
SURF COMBINES WITH THE KING TIDE. AREAS THAT TYPICALLY FLOOD DURING
KING TIDES WILL VERY LIKELY FLOOD WITHIN A COUPLE HOURS BEFORE TO
A COUPLE HOURS AFTER THE DAILY HIGHEST TIDES. THE NEXT HIGH TIDE
AT SAN FRANCISCO IS EXPECTED ON SUNDAY AT 11:26 AM, WITH A HEIGHT
OF 6.89 FEET.
MTR WATCHES/WARNINGS/ADVISORIES
CA...COASTAL FLOOD ADVISORY UNTIL 4 PM PST MONDAY FOR CAZ006-506-508.
PZ...SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 3 AM PST MONDAY
FOR SF BAY N OF BAY BRIDGE.
SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 9 PM PST MONDAY
FOR PIGEON PT TO PT PINOS 10-60 NM-PT ARENA TO PT REYES 0-
10 NM-PT ARENA TO PT REYES 10-60 NM-PT REYES TO PIGEON PT 0-
10 NM.
SMALL CRAFT ADVISORY FROM 9 PM THIS EVENING TO 9 PM PST MONDAY
FOR PIGEON PT TO PT PINOS 0-10 NM-PT PINOS TO PT PIEDRAS
BLANCAS 0-10 NM.
SHORT TERM...BEHRINGER
LONG TERM....BEHRINGER
AVIATION...RGASS
MARINE...MM
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