293
FXUS61 KBOX 091130
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
730 AM EDT SAT MAY 9 2026
WHAT HAS CHANGED
TRENDS HAVE SHIFTED THE MAIN RAIN AXIS FATHER SOUTH, SO WIDESPREAD
RAINFALL SUNDAY NIGHT INTO MONDAY NOW LOOKS LESS LIKELY THAN
BEFORE.
KEY MESSAGES
- MOTHER’S DAY WEEKEND LOOKS SPLIT, WITH WIDESPREAD SHOWERS AND
COOLER TEMPERATURES TODAY FOLLOWED BY SOMEWHAT WARMER AND
MAINLY DRIER CONDITIONS SUNDAY.
- NOTABLE CHANGES TO THE RAINFALL FORECAST SUNDAY NIGHT INTO
MONDAY, WIDESPREAD RAINFALL IS LOOKING LESS LIKELY.
- BRIEFLY DRY TUESDAY, PERHAPS TURNING UNSETTLED WEDNESDAY INTO
THURSDAY.
DISCUSSION
KEY MESSAGE 1...MOTHER’S DAY WEEKEND LOOKS SPLIT, WITH WIDESPREAD
SHOWERS AND COOLER TEMPERATURES TODAY FOLLOWED BY SOMEWHAT WARMER
AND MAINLY DRIER CONDITIONS SUNDAY.
AS AN UPPER TROUGH DIGS INTO THE GREAT LAKES, A WARM FRONT LIFTS
NORTH OF SOUTHERN NEW ENGLAND THIS MORNING. INCREASING LARGE-SCALE
FORCING COMBINED WITH A STRENGTHENING SOUTHERLY LOW-LEVEL JET WILL
SUPPORT SCATTERED SHOWERS DEVELOPING DURING THE MORNING HOURS,
BECOMING WIDESPREAD FROM WEST TO EAST DURING THE AFTERNOON AND EARLY
EVENING AS THE MAIN SHORTWAVE AND PRE-FRONTAL TROUGH APPROACH THE
REGION. THIS IS CAPTURED WELL BY THE 00Z SUITE OF HIGH-RES CAMS AND
ALIGNS WELL WITH NBM POPS FOR THIS MORNING AND EVENING.
AS A MOISTENING AIRMASS OVERSPREADS THE REGION, A STRENGTHENING
SOUTHERLY LOW-LEVEL JET DEVELOPS THIS AFTERNOON INTO SATURDAY
EVENING, ENHANCING LIFT AND FOCUSING MOISTURE TRANSPORT ACROSS
SOUTHERN NEW ENGLAND. NEAR THE NOSE OF THE LLJ, MAINLY ACROSS RI AND
SOUTHEAST MA, MODEST ELEVATED INSTABILITY MAY SUPPORT BRIEF HEAVY
DOWNPOURS AND AN ISOLATED EMBEDDED THUNDERSTORM; HOWEVER, WIDESPREAD
THUNDER IS NOT EXPECTED. PWATS INCREASE TO AROUND 0.8–1.0 INCHES PER
THE 00Z HREF, NEAR CLIMATOLOGICAL NORMALS FOR EARLY MAY. ENSEMBLE
GUIDANCE CONTINUES TO SHOW A MODERATE CHANCE OF A BENEFICIAL WETTING
RAIN, WITH GEFS PROBABILITIES AROUND 40–50 PERCENT FOR AMOUNTS OVER
0.50 INCHES AND ECMWF ENSEMBLE PROBABILITIES OF 70–90 PERCENT ACROSS
COASTAL RI AND SOUTHEAST MA. THIS SUPPORTS RAINFALL AMOUNTS OF
0.30–0.60 INCHES, WITH LOCALLY HIGHER AMOUNTS POSSIBLE IN HEAVIER
SHOWERS OR ANY EMBEDDED CONVECTION. FLOODING CONCERNS REMAIN LOW
GIVEN RECENT DRY CONDITIONS. CLOUDS, ONSHORE FLOW, AND RAINFALL WILL
KEEP TEMPERATURES COOL, WITH HIGHS MAINLY IN THE MID 50S TO LOWER
60S. MILD AND SOMEWHAT HUMID CONDITIONS PERSIST TONIGHT WITH LOWS
ONLY FALLING INTO THE UPPER 40S TO LOWER 50S AMID CONTINUED LOW
CLOUDS AND AREAS OF FOG.
CONDITIONS IMPROVE HEADING INTO SUNDAY AS SUBTLE MID-LEVEL HEIGHT
RISES SUPPORT QUIETER AND MILDER WEATHER FOR MOTHER’S DAY. WHILE
SOUTHWEST TO WEST-SOUTHWEST FLOW PERSISTS, A NOTABLY DRIER AIRMASS
IS NOT EXPECTED TO MOVE INTO SOUTHERN NEW ENGLAND. IN FACT,
DEWPOINTS CLIMB INTO THE LOW TO MID 50S, MAKING IT FEEL SOMEWHAT
MORE HUMID COMPARED TO THE MUCH DRIER CONDITIONS OBSERVED LATE THIS
WEEK. GIVEN LINGERING MOISTURE, EMBEDDED SHORTWAVE ENERGY WITHIN THE
FLOW, AND AN APPROACHING COLD FRONT, CANNOT COMPLETELY RULE OUT A
PASSING AFTERNOON SHOWER OR THUNDERSTORM, AS A FEW HUNDRED J/KG OF
CAPE MAY DEVELOP. THAT SAID, SUNDAY DOES NOT APPEAR TO BE A WASHOUT,
THOUGH THOSE WITH OUTDOOR PLANS SHOULD REMAIN WEATHER AWARE.
AFTERNOON HIGHS HAVE TRENDED A FEW DEGREES LOWER, MAINLY DUE TO THE
AMOUNT OF CLOUD COVER; NEVERTHELESS, HIGHS REMAIN COMFORTABLE IN THE
UPPER 60S TO LOWER 70S.
KEY MESSAGE 2...NOTABLE CHANGES TO THE RAINFALL FORECAST SUNDAY
NIGHT INTO MONDAY, WIDESPREAD RAINFALL IS LOOKING LESS LIKELY.
THERE IS A NOTABLE CHANGE TO THE FORECAST AS THE PREVIOUSLY
ADVERTISED SECOND ROUND OF BENEFICIAL RAINFALL LATE SUNDAY NIGHT
INTO MONDAY IS LOOKING LESS LIKELY. A MID-LEVEL TROUGH AND EMBEDDED
SHORTWAVE MOVE INTO THE NORTHEAST, WITH THE BEST FORCING NOW
SHIFTING SOUTH OF SOUTHERN NEW ENGLAND. A SURFACE LOW IS EXPECTED TO
DEVELOP SOUTHEAST OF THE BENCHMARK (40N, 70W) BEFORE TRACKING INTO
THE NORTH ATLANTIC.
MODEL GUIDANCE OVER THE PAST 24 HOURS HAS SHOWN A NOTABLE SOUTHWARD
SHIFT IN THE AXIS OF PRECIPITATION, MAINLY OFFSHORE OF SOUTHERN NEW
ENGLAND, THOUGH AREAS FROM NEW HAVEN TO WOONSOCKET TO BOSTON AND
POINTS SOUTHEAST HAVE THE GREATEST POTENTIAL FOR RAINFALL, ALBEIT
LESS THAN PREVIOUSLY EXPECTED. GEFS AND ECMWF ENSEMBLE GUIDANCE ARE
IN FAIRLY GOOD AGREEMENT, WITH PROBABILITIES OF 24-HOUR RAINFALL
GREATER THAN 0.50 INCHES NOW BELOW 30 PERCENT. NANTUCKET AND OUTER
CAPE COD MAINTAIN HIGHER PROBABILITIES IN THE 50–60 PERCENT RANGE.
ONE OUTLIER REMAINS THE NAM 12 KM, WHICH CONTINUES TO DEPICT A MORE
WIDESPREAD RAINFALL SOLUTION.
THAT SAID, THERE REMAIN LOW CHANCES OF PRECIPITATION ACROSS INTERIOR
SOUTHERN NEW ENGLAND, WITH ANY ACTIVITY MORE LIKELY IN THE FORM OF
DIURNALLY DRIVEN SHOWERS RATHER THAN A WIDESPREAD STRATIFORM RAIN
EVENT. TEMPERATURES MONDAY AFTERNOON TREND 8–12 DEGREES COOLER THAN
SUNDAY, RESULTING IN A NOTICEABLY COOLER FEEL.
KEY MESSAGE 3...BRIEFLY DRY TUESDAY, PERHAPS TURNING UNSETTLED
WEDNESDAY INTO THURSDAY.
THE MID-LEVEL TROUGH SHIFTS OFFSHORE ON TUESDAY, WITH MID-LEVEL
RIDGING DEVELOPING IN ITS WAKE. FLOW ALOFT TURNS NORTH-NORTHWEST,
ADVECTING LOWER HUMIDITY AND COOLER TEMPERATURES INTO THE REGION,
LEADING TO A COOL BUT SUNNY DAY.
THIS IS SHORT-LIVED, AS UNSETTLED CONDITIONS MAY RETURN BY WEDNESDAY
AND CONTINUE INTO THURSDAY AS ANOTHER MID-LEVEL TROUGH AND EMBEDDED
SHORTWAVE MOVE THROUGH THE NORTHEAST, THOUGH CONFIDENCE IN TIMING
AND IMPACTS REMAINS LOW GIVEN THE LONGER FORECAST RANGE. HIGH
TEMPERATURES REMAIN NEAR TO SLIGHTLY BELOW CLIMATOLOGICAL NORMALS
FOR MID-MAY, MODERATING INTO THE UPPER 50S TO LOWER 60S TUESDAY
THROUGH THURSDAY.
AVIATION /12Z SATURDAY THROUGH WEDNESDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
12Z TAF UPDATE:
THROUGH TONIGHT: MODERATE CONFIDENCE.
VFR CEILINGS/VISBYS WITH INITIAL -SHRA 13-15Z SAT, WHICH TENDS
TO LIFT N/NE. PERIOD OF RELATIVELY DRY WEATHER (WOULDN'T RULE
OUT A SPOT -SHRA ESPECIALLY NORTH OF BED, BUT GENERALLY DRY)
THRU 17Z. THEN A PERIOD OF WIDESPREAD STEADY RAINS WITH MVFR-
IFR CEILINGS/VISBYS SPREADS EASTWARD BETWEEN 17Z-22Z. TEMPO'D IN
POTENTIAL FOR SOME HEAVIER DOWNPOURS OR A RUMBLE/TWO OF THUNDER
FROM BDL-PVD SOUTH AND EAST. STEADIER RAIN COMES TO AND END
00-03Z WEST TO EAST, BUT TRAPPED MOISTURE SUPPORTS WIDESPREAD
IFR CEILINGS WITH POSSIBLE MIST/FOG INTO THE EVENING/OVERNIGHT.
WINDS START OFF LIGHT ESE TO S WINDS, BUT SPEEDS WILL BE PICKING
UP TO AROUND 8-12 KT BY THIS AFTERNOON, WITH S/SW WINDS UNDER 10
KT BY TONIGHT. POSSIBLE AREAS OF LOW-LEVEL WIND SHEAR ALONG THE
SOUTH COAST/CAPE AND ISLANDS ONCE RAIN ENDS AND SOUTHERLY
WINDSPEEDS EASE SOME.
SUNDAY...MODERATE CONFIDENCE.
LOW-END VFR. CHANCE OF A POP-UP SHOWER DURING THE AFTERNOON. SW
WINDS 8-12 KT WITH SOME GUST TO 20 KT.
KBOS TERMINAL...MODERATE CONFIDENCE IN TAF. VFR UNRESTRICTED
LIGHT -SHRA THRU 14Z, THEN GENERALLY DRY THRU AT LEAST 19Z.
THEN A PERIOD OF MVFR SHRA 19-20Z THRU 02Z, RUMBLE OF THUNDER
POSSIBLE BUT NOT AS LIKELY AS SOUTHEAST MA. CEILINGS THEN DROP
TO IFR LEVELS ONCE RAIN ENDS. WINDS START OFF LIGHT ESE BUT
SPEEDS INCREASE TO AROUND 10-12 KT THIS AFTERNOON, THEN BECOMING
LIGHT SOUTH AS RAIN ENDS.
KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. VFR UNRESTRICTED
LIGHT -SHRA THRU 13Z, THEN GENERALLY DRY THRU AT LEAST 17Z.
THEN A PERIOD OF MVFR SHRA 17-18Z THRU 00Z, RUMBLE OF THUNDER
POSSIBLE. CEILINGS THEN DROP TO IFR LEVELS ONCE RAIN ENDS.
WINDS START OFF LIGHT NORTHERLY, THEN FLIP TO SE BY MID-
MORNING WITH INCREASE TO AROUND 10-12 KT THIS AFTERNOON, THEN
BECOMING LIGHT SOUTH AS RAIN ENDS.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT THROUGH MONDAY: VFR. CHANCE SHRA.
MONDAY NIGHT THROUGH TUESDAY NIGHT: VFR.
WEDNESDAY: VFR. SLIGHT CHANCE SHRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH SUNDAY...HIGH CONFIDENCE.
AN AREA OF LOW PRESSURE TRACKS WELL INLAND ON SATURDAY, A WARM FRONT
LIFTING NORTH DURING THE DAY AND PERIODS OF RAIN AND EMBEDDED
THUNDERSTORMS. A WIND SHIFT TO THE S-SSE AND INCREASING WIND SPEEDS
15 TO 20 KT AND GUST 25+ KT. SEAS INCREASING FROM S TO N AS WELL
THROUGHOUT THE DAY 4 TO 7 FT LEADING TO A SMALL CRAFT ADVISORY TODAY
INTO EARLY SUNDAY. SW TO S WIND SUNDAY WITH GUSTS LESS THAN 20 KT
AND SEAS BELOW 5 FT.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
MONDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
RAIN SHOWERS LIKELY.
MONDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
TUESDAY THROUGH TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS
LOCALLY APPROACHING 5 FT.
WEDNESDAY: WINDS LESS THAN 25 KT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY FROM NOON TODAY TO 2 AM EDT SUNDAY FOR
ANZ231>235-237-251.
SMALL CRAFT ADVISORY FROM NOON TODAY TO 8 AM EDT SUNDAY FOR
ANZ250-254>256.
DISCUSSION...DOOLEY
AVIATION...LOCONTO/DOOLEY
MARINE...DOOLEY
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