477
FXUS61 KBOX 231106
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
706 AM EDT SAT SEP 23 2023
SYNOPSIS
A PATTERN CHANGE THIS WEEKEND, WITH PERIODS OF RAIN, GUSTY NORTHEAST
WINDS AND COOLER THAN NORMAL TEMPERATURES, AS MOISTURE FROM OPHELIA
STREAMS NORTHWARD INTO SOUTHERN NEW ENGLAND. RAIN EXITS SOMETIME
MONDAY MORNING, FOLLOWED BY A DRYING TREND THE REST OF NEXT WEEK, AS
LARGE SPRAWLING HIGH PRESSURE BUILDS FROM QUEBEC INTO NEW ENGLAND.
THIS HIGH WILL INITIALLY BE ACCOMPANIED BY AN OCTOBER-LIKE AIRMASS,
WITH HIGHS ONLY 60-65 AND LOWS IN THE 40S EARLY NEXT WEEK. THIS
AIRMASS SLOWLY MODIFIES WITH HIGHS REBOUNDING TO NEAR 70 LATE NEXT
WEEK.
NEAR TERM /UNTIL 6 PM THIS EVENING/
7 AM UPDATE...
TOUGH FORECAST TODAY, WITH LOTS OF DRY AIR OVER SNE IN RESPONSE
TO CONFLUENT FLOW AND SUBSIDENCE ACROSS MAINE. THIS AREA OF MID
LEVEL CONFLUENT FLOW DOESN'T MOVE MUCH TODAY, HENCE, DRY AIR
WILL BE TOUGH TO ERODE. AS RAIN SHIELD ADVANCES NORTH IT WILL
BECOME FRAGMENT AS DRY AIR ERODES PRECIP. THEREFORE, WE FOLLOWED
THE DRIER/MORE SUPPRESSED SOLUTIONS FOR TODAY'S FORECAST. THIS
TRANSLATES TO STEADY RAINS ACROSS CT/RI AND SOUTHEAST MA THIS
AFTERNOON, SOUTH OF THE MASS PIKE, WITH HEAVIEST RAINS OVER
SOUTHEAST MA, CAPE COD AND THE ISLANDS. NORTH OF THE MASS PIKE,
VERY LIGHT RAIN THIS AFTERNOON. IN FACT, ALONG THE NH/MA, MA/VT
BORDER, THERE MAY NOT BE MUCH RAIN AT ALL TODAY. AGAIN,
CHALLENGING FORECAST. OTHERWISE, PREVIOUS FORECASTS AND
DISCUSSION BELOW HAVE A GOOD HANDLE ON CURRENT CONDITIONS.
HENCE, NO MAJOR CHANGES WITH THIS UPDATE. EARLIER DISCUSSION
BELOW.
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SURGE OF HIGHER PWATS OVERSPREADING THE REGION FROM THE SOUTH WILL
BRING RAIN NORTHWARD INTO SNE TODAY. BIGGEST FORECAST CHALLENGE IS
DETERMINING NORTHWARD EXTENT OF RAINFALL AS WELL AS RAINFALL
AMOUNTS. CONFLUENT FLOW TO THE NORTH WILL MAINTAIN HIGH PRES AND
AREA OF LOW-MID LEVEL DRY AIR WHICH EXTENDS SOUTH INTO SNE TO START
THE DAY. THIS WILL INITIALLY ERODE NORTHERN EXTENT OF RAINFALL AS IT
LIFTS NORTHWARD AND RESULT IN A TIGHT QPF GRADIENT ACROSS SNE.
DEEPEST MOISTURE AND BEST FORCING ASSOCD WITH EASTERLY LOW LEVEL JET
LIFTING NORTH INTO THE REGION WILL BE FOCUSED ALONG THE SOUTH COAST
AND ESPECIALLY THE ISLANDS WHERE HEAVIEST RAINFALL WILL OCCUR,
ESPECIALLY DURING THE AFTERNOON. RAINFALL COVERAGE AND AMOUNTS MORE
UNCERTAIN FURTHER N ACROSS SNE. RAIN OVERSPREADS RI, SE MA AND
PORTIONS OF NORTHERN CT THIS MORNING, AND NORTHERN EXTENT OF
RAIN SHOULD REACH THE MASS PIKE IN THE AFTERNOON. HOWEVER, GIVEN
THAT THE COLUMN NEVER TRULY SATURATES IN NORTHERN MA, THINK IT
WILL BE A STRUGGLE TO GET RAIN MUCH FURTHER N THAN ROUTE 2
CORRIDOR FOR MUCH OF THE DAY WITH JUST SOME SPOTTY LIGHT RAIN
POSSIBLE HERE LATER IN THE DAY. POPS TODAY WILL RANGE FROM 100
PERCENT NEAR THE SOUTH COAST TO 20-30 PERCENT IN FAR NORTHERN
MA.
A PERIOD OF HEAVY RAIN IS LIKELY THIS AFTERNOON, ESPECIALLY
CAPE/ISLANDS POSSIBLY EXTENDING NORTH TO THE SOUTH COAST AS LOW
LEVEL JET ENHANCES ISENTROPIC LIFT/FGEN. ALSO, LOW RISK FOR
ISOLATED THUNDER OVER THE ISLANDS WITH SOME ELEVATED INSTABILITY
DEVELOPING OVER THE OCEAN. RAINFALL AMOUNTS THROUGH TODAY UP TO
AN INCH POSSIBLE NEAR THE SOUTH COAST AND 1-2 INCHES OVER THE
ISLANDS, DECREASING TO LESS THAN 0.10" FAR NORTHERN MA.
HIGHS WILL RANGE FROM THE UPPER 50S HIGHER TERRAIN TO 60-65
ELSEWHERE. BECOMING WINDY THIS AFTERNOON OVER THE ISLANDS AND
IMMEDIATE SOUTH COAST WITH NE GUSTS 25-35 MPH AS A MODEST LOW
LEVEL JET LIFTS INTO THE REGION.
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/
TONIGHT...
INTENSITY OF RAINFALL OVER THE CAPE/ISLANDS SHOULD DIMINISH THIS
EVENING AS THE LOW LEVEL JET WEAKENS, BUT PERIODS OF RAIN OR DRIZZLE
ARE EXPECTED TONIGHT AS DEEP MOISTURE PLUME REMAINS ACROSS THE
REGION WHILE LIFTING NORTH. GUSTY SOUTH COASTAL WINDS WILL DIMINISH
OVERNIGHT WITH LOWS MOSTLY IN THE 50S.
SUNDAY...
REMNANTS OF OPHELIA WILL BE LIFTING NORTH ALONG THE MID ATLC COAST
WHICH WILL BRING ANOTHER ROUND OF RAIN/SHOWERS INTO SNE. STILL SOME
UNCERTAINTY WITH TIMING AND RAINFALL COVERAGE/AMOUNTS WITH THIS
SECOND ROUND OF RAINFALL GIVEN THE VARIANCE IN THE MODEL GUIDANCE.
BUT POTENTIAL FOR AT LEAST LIGHT TO MODERATE RAINFALL, ESPECIALLY IN
THE AFTERNOON IN CT/RI AS MOISTURE MOVES IN FROM THE SW. HIGHS WILL
BE IN THE 60S WITH NE WINDS 10-20 MPH.
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
HIGHLIGHTS:
* RAIN SUNDAY NIGHT SPILLS INTO EARLY MONDAY, BUT THEN EXITS
YIELDING A DRY FINISH TO THE DAY MONDAY
* COOL, OCTOBER-LIKE AIRMASS ARRIVES MON NIGHT INTO TUE AND IS
ACCOMPANIED BY GUSTY NE WINDS, ESPECIALLY ACROSS SOUTHEAST MA
* LARGE SPRAWLING 1035 MB HIGH PRESSURE BUILDS FROM QUEBEC SOUTHWARD
INTO NEW ENGLAND NEXT WEEK, YIELDING DRY BUT COOL WEATHER. CORE OF
COOL AIR IS MON NGT/TUE, THEN SLOWLY REBOUNDING MID TO LATE WEEK.
DETAILS:
SUNDAY NIGHT AND MONDAY:
REMNANT LOW FROM OPHELIA AND ITS TROPICAL MOISTURE PLUME WILL STREAM
ACROSS SNE SUNDAY NIGHT, YIELDING A STEADY LIGHT TO MODERATE RAIN,
POSSIBLY HEAVY AT TIMES. MOST OF THE GUIDANCE, INCLUDING EC AND CMC
ENSEMBLES AND DETERMINISTIC OUTPUT, INCLUDING UKMET SUGGEST DEEPEST
MOISTURE AND BEST FORCING FOR ASCENT IS ACROSS CT-RI AND POSSIBLY UP
TO THE MASS PIKE. GFS AND ITS ENSEMBLES OFFER A MORE SUPPRESSED
SOLUTION WITH RAIN CHANCES CONFINED TO THE SOUTH COAST. WE WILL
FOLLOW MODEL CONSENSUS/NON-GFS SOLUTION HERE AND GO WITH THE WETTER
OUTCOME FOR CT-RI AND ALONG/SOUTH OF THE MASS PIKE. WITH CONFLUENT
FLOW JUST TO THE NORTH OF SNE, THERE SHOULD BE A SHARP CUTOFF IN QPF
FROM SOUTH TO NORTH. THIS IS SOMETHING WE WILL HAVE TO WATCH AND IS
WHAT THE GFS AND ITS ENSEMBLES HAVE LATCHED ONTO. UPSTREAM MID
LEVEL TROUGH KICKS REMNANT OPHELIA LOW SEAWARD LATER MONDAY. THUS,
MONDAY BEGINS WET BUT PROBABLY ENDS DRY FROM N TO S. COOL, BREEZY
AND RAW WITH ONSHORE NE WINDS. HIGHS ONLY IN THE MID TO UPPER 60S,
BUT WILL FEEL COOLER GIVEN THE GUSTY NORTHEAST WINDS, ESPECIALLY
ACROSS SOUTHEAST MA.
TUESDAY THROUGH FRIDAY:
THIS PORTION OF THE FORECAST PERIOD WILL BE DOMINATED BY A POSITIVE
HEIGHT ANOMALY DRIFTING ACROSS ONTARIO AND EVENTUALLY INTO QUEBEC.
AT THE SURFACE, THIS FEATURE IS ACCOMPANIED BY 1030+ MB ANTICYCLONE
THAT ADVECTS SOUTHWARD FROM QUEBEC INTO SOUTHERN NEW ENGLAND. THIS
INITIALLY WILL BE ACCOMPANIED BY A CHILLY AIRMASS, WITH CORE OF COOL
AIR (+8C) AT 925 MB MON NIGHT INTO TUE. THIS WILL LIMIT HIGHS
TUESDAY TO 60-65, FOLLOWED BY TUE NIGHT MINS IN THE 40S. GIVEN THE
GUSTY NE WINDS, DEFINITELY FEELING MORE LIKE OCTOBER THAN SEP. THIS
DEEP LAYER RIDGE WILL ALSO PROVIDE DRY WEATHER MUCH OF NEXT WEEK.
THE AIRMASS SLOWLY MODIFIES WITH HIGHS REBOUNDING TO AROUND 70 BY
THU/FRI.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
FORECAST CONFIDENCE
LEVELS:
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
11Z TAF UPDATE: NO CHANGES. RAIN SHIELD WILL STRUGGLE TO MOVE
NORTHWARD AND WILL BECOME FRAGMENTED AS DRY AIR ERODES LEADING
EDGE OF PRECIP.
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THROUGH 12Z...
PATCHY MVFR CIGS FROM SOUTH COAST TO SE MA, OTHERWISE VFR.
TODAY...MODERATE CONFIDENCE.
MVFR CIGS EXPANDING NORTHWARD TO NEAR THE MASS PIKE IN THE
AFTERNOON, WITH IFR DEVELOPING ACROSS RI/SE MA. MAINLY VFR CIGS
INTERIOR NORTHERN AND WESTERN MA. RAIN LIFTS NORTH FROM THE
SOUTH COAST IN THE MORNING, REACHING MASS PIKE REGION IN THE
AFTERNOON, BUT UNCERTAIN HOW FAR NORTH INTO NORTHERN MA RAIN
GETS. LOCALLY HEAVY RAINFALL POSSIBLE CAPE/ISLANDS THIS
AFTERNOON. NE GUSTS TO 25 KT DEVELOPING ALONG THE SOUTH COAST
IN THE AFTERNOON, UP TO 30 KT OVER THE ISLANDS.
TONIGHT...MODERATE CONFIDENCE
MVFR/IFR CONDITIONS WITH AREAS OF RAIN AND DRIZZLE. NE GUSTS
20-25 KT SOUTH COAST AND 25-30 KT OVER THE ISLANDS IN THE
EVENING, THEN DIMINISHING OVERNIGHT.
SUNDAY...MODERATE CONFIDENCE.
MAINLY MVFR CONDITIONS WITH AREAS OF IFR. ANOTHER ROUND OF
RAIN/SHOWERS LIKELY OVERSPREADING THE REGION FROM SW.
KBOS TAF...HIGH CONFIDENCE IN TRENDS, MODERATE ON TIMING.
SHOULD REMAIN VFR THROUGH THE MORNING, THEN LOWERING TO MVFR IN
THE AFTERNOON AS RAIN OVERSPREADS THE REGION. UNCERTAINTY ON
NORTHERN EXTENT OF IFR CIGS BUT KEPT THESE LOWER CIGS TO THE
SOUTH.
KBDL TAF...HIGH CONFIDENCE IN TRENDS, MODERATE ON TIMING. VFR IN
THE MORNING LOWERING TO MVFR IN THE AFTERNOON AS RAIN
OVERSPREADS THE REGION.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY.
CHANCE SHRA.
MONDAY: VFR. WINDY WITH LOCAL GUSTS UP TO 30 KT. SLIGHT CHANCE
SHRA.
MONDAY NIGHT THROUGH TUESDAY: VFR. WINDY WITH LOCAL GUSTS UP TO
30 KT.
TUESDAY NIGHT THROUGH WEDNESDAY: VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
GALE WARNINGS WILL REMAIN IN PLACE FOR MUCH OF THE SOUTH COASTAL
WATERS FOR A PERIOD OF MARGINAL GALE FORCE NE WINDS WITH GUSTS 30-35
KT THIS AFTERNOON AND EVENING. BEST CHANCE OF GALES WILL BE ACROSS
RI COASTAL WATERS TO WATERS SOUTH OF NANTUCKET. WINDS GRADUALLY
DIMINISH TONIGHT INTO SUNDAY. ROUGH SEAS PEAKING LATE AFTERNOON AND
EVENING, UP TO 10-12 FT SOUTHERN WATERS, THEN SLOWLY SUBSIDING
THROUGH SUNDAY. HEAVY RAIN AND ISOLATED THUNDER OVER SOUTH COASTAL
WATERS TODAY WITH REDUCED VSBYS. PERIOD OF RAIN/SHOWERS AND
PATCHY FOG CONTINUE TONIGHT INTO SUNDAY.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF
RAIN SHOWERS.
MONDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 30 KT. SEAS UP TO 5 FT. SLIGHT CHANCE OF RAIN SHOWERS.
MONDAY NIGHT: STRONG WINDS WITH GUSTS UP TO 35 KT. ROUGH SEAS
UP TO 7 FT.
TUESDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. SEAS UP TO 5 FT.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
WEDNESDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...HIGH RISK FOR RIP CURRENTS THROUGH THIS EVENING FOR MAZ020-022>024.
RI...HIGH RISK FOR RIP CURRENTS THROUGH THIS EVENING FOR RIZ006>008.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT SUNDAY FOR ANZ231-236.
GALE WARNING FROM 2 PM THIS AFTERNOON TO 2 AM EDT SUNDAY FOR
ANZ232>235-237.
SMALL CRAFT ADVISORY FROM 2 PM THIS AFTERNOON TO 8 PM EDT
SUNDAY FOR ANZ250.
SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 8 PM EDT SUNDAY
FOR ANZ251.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT SUNDAY FOR ANZ254.
GALE WARNING FROM 11 AM THIS MORNING TO 2 AM EDT SUNDAY FOR
ANZ255-256.
SYNOPSIS...KJC/NOCERA
NEAR TERM...KJC/NOCERA
SHORT TERM...KJC
LONG TERM...NOCERA
AVIATION...KJC/NOCERA
MARINE...KJC/NOCERA
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