862
FXUS61 KBOX 060528
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
ISSUED BY NATIONAL WEATHER SERVICE GRAY ME
128 AM EDT TUE MAY 6 2025
SYNOPSIS
UNSETTLED WEATHER WILL CONTINUE MUCH OF THIS WEEK WITH
SHOWERS AND ISOLATED THUNDERSTORMS THAT WILL PRODUCE HEAVY
RAINFALL AT TIMES. A FLOOD WATCH IS IN EFFECT STARTING TONIGHT
INTO TUESDAY FOR INTERIOR SOUTHERN NEW ENGLAND. APPEARS WE MAY
BRIEFLY DRY OUT BY THURSDAY, BEFORE MORE RAIN ARRIVES FRIDAY
INTO SATURDAY.
NEAR TERM /THROUGH TODAY/
KEY MESSAGES:
* STEADY RAINS WITH EMBEDDED DOWNPOURS MOVES INTO THE INTERIOR
TONIGHT AND OVERNIGHT THEN MOVES EAST INTO EASTERN MA/RI
OVERNIGHT TO EARLY TUE. STREET FLOODING POSSIBLE.
* FLOOD WATCH IN EFFECT TONIGHT THROUGH 8 PM TUESDAY FOR ALL OF
NORTHERN CT AND WESTERN/CENTRAL MASSSCHUSETTS.
* LITTLE TO NO CHANGE IN TEMPS TONIGHT.
DETAILS...
OTHER THAN SOME PARTIAL CLEARING OVER THE CAPE AND ISLANDS, IT'S
OTHERWISE BEEN AN OVERCAST, DREARY, MISTY AND RAW MONDAY ACROSS
THE MAJORITY OF SOUTHERN NEW ENGLAND WITH NORTHEAST WINDS AND
TEMPS IN THE 50S. OUR WEATHER PATTERN IS BEING GOVERNED BY A
SLOW-MOVING AND WOUND-UP UPPER LEVEL LOW OVER THE OHIO VALLEY
AND A STRONG 1030+ MB RIDGE OF HIGH PRESSURE OVER NORTHEAST ME.
SOUTHEAST FLOW IS EXPECTED TO INCREASE QUITE A BIT TONIGHT,
TAPPING INTO A MOISTURE FEED OF SUBTROPICAL ORIGIN WHICH WILL
CAUSE PRECIPITABLE WATER VALUES TO RISE TO AROUND 1.4 TO 1.6"
PER THE LATEST SREF GUIDANCE. AN INITIAL BAND OF PASSING SHOWERS
WAS MOVING INTO WESTERN NEW ENGLAND, HOWEVER WE EXPECT THE FIRST
OF AT LEAST A COUPLE PERIODS OF FOCUSED RAINS AND EMBEDDED
DOWNPOURS TO PROGRESS NNW FROM THE OCEAN IN THE PREVAILING SE
FLOW. WE EXPECT THIS INITIAL ROUND OF RAIN TO BE ENHANCED BY AN
ELEMENT OF UPSLOPE FLOW AGAINST THE BERKSHIRES, LITCHFIELD AND
TOLLAND HILLS AND HILLS IN WORCESTER COUNTY. RAINS WITH EMBEDDED
DOWNPOURS WILL INITIALLY BEGIN IN WESTERN NEW ENGLAND, THEN
GRADUALLY SHIFT EASTWARD INTO CENTRAL AND EASTERN MA AND RI
TOWARD OVERNIGHT TO EARLY TUESDAY MORNING. AREAL-AVERAGED RAIN
TOTALS OF 1-1.5" ARE POSSIBLE IN INTERIOR SOUTHERN NEW ENGLAND
THROUGH TUESDAY MORNING, AND AROUND A HALF INCH OR LESS FOR
EASTERN MA AND MOST OF RI.
WE'VE ISSUED A FLOOD WATCH FOR ALL OF NORTHERN CT AND WESTERN
AND CENTRAL MA STARTING TONIGHT, WHICH CARRIES OVER INTO
TUESDAY. MORE DETAILS ON THE METEOROLOGY AND HYDROLOGY CAN BE
FOUND IN THE BELOW HYDROLOGY SECTION, BUT WE COULD SEE SCATTERED
INSTANCES OF STREET FLOODING IN URBAN AND POOR DRAINAGE AREAS
AS WELL AS RISES ON STREAMS AND CREEKS.
TEMPS ARE UNLIKELY TO GO VERY FAR FROM CURRENT VALUES IN THE
50S GIVEN THE COOLER ONSHORE NE FLOW IN PREVAILING SE/S WARM
ADVECTION PATTERN.
SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/
KEY MESSAGES:
* BRIEF BREAK IN RAINS TUE MORNING, BUT ANOTHER ROUND OF STEADY
RAIN AND EMBEDDED DOWNPOURS FOR THE AFTERNOON. STREET FLOODING
COULD BE POSSIBLE. FLOOD WATCH IN EFFECT.
* TRENDING "DRIER" TUE NIGHT BUT HAVE TO WATCH FOR POSSIBLE
PATCHY FOG.
DETAILS:
TUESDAY:
THE INITIAL SLUG OF HEAVIER RAINS FOR TONIGHT INTO EARLY ON TUE
THEN MOVES OFFSHORE DURING THE EARLY TO MID-MORNING TUE HOURS.
STILL OVERCAST AND DREARY, BUT AT LEAST INTO MID-MORNING, IT IS
SOMETHING OF A RELATIVE BREAK.
THEN INTO THE LATE MORNING HOURS, A SECOND ROUND OF STEADIER
RAINS LOOKS TO RE-DEVELOP AND MOVE ENE, FOLLOWING THE SLOW-
EASTWARD PASSAGE OF THE RICH SUBTROPICAL MOISTURE PLUME. THERE
COULD BE SOME ISOLATED RUMBLES OF THUNDER WITH THIS SECOND ROUND
AND COVERAGE PROBABLY TURNS MORE WIDESPREAD. BUT WITH THE
RICHER MOISTURE AXIS MOVING MORE OFFSHORE, RAIN TOTALS ARE (1) A
LITTLE LIGHTER AND (2) MORE FOCUSED INTO CENTRAL AND EASTERN MA
AND RI. RAIN TOTALS OF AROUND 0.75 TO 1" IN EASTERN MA/RI, WITH
TOTALS AROUND A HALF TO THREE QUARTERS OF AN INCH IN INTERIOR
SOUTHERN NEW ENGLAND. FLOOD WATCH WAS EXTENDED INTO THIS
FORECAST PERIOD AS WELL. SHOWER COVERAGE SHOULD BE DIMINISHING
INTO THE INTERIOR LATE IN THE DAY, BUT MAY STILL BE CONTINUING
IN EASTERN AREAS.
SOME GUARDED OPTIMISM HIGHS COULD REACH INTO THE LOWER TO MID
60S BUT IT WILL STILL BE FAR FROM AN IDEAL MAY DAY.
TUESDAY NIGHT:
CHANCES FOR RAINS THEN START TO DIMINISH TUE NIGHT AS THE UPPER
LEVEL LOW BEGINS TO FILL/WEAKEN AND STARTS TO SHIFT EASTWARD
INTO THE NORTHERN MID-ATLANTIC REGION. WILL HAVE A PERIOD OF
925-700 MB COOL ADVECTION ON WSW WINDS AND WE COULD BEGIN TO
SHAKE FREE OF CLOUDINESS; WHAT WE'LL HAVE TO WATCH IF WE DO LOSE
THE CLOUD COVER IS PATCHY FOG. LOWS STILL QUITE MILD IN THE MID
50S.
LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/
KEY POINTS
* SCATTERED SHOWERS/POSSIBLE T-STORMS WITH SMALL HAIL POSSIBLE
WED.
* BRIEF DRY AND MILD WEATHER FOR A CHANGE THURS
* LOOKING UNSETTLED WITH RAIN LIKELY, ALTHOUGH THE DETAILS STILL
ARE UNCERTAIN.
WEDNESDAY:
UPPER LOW CONTINUES TO DEAMPLIFY AND ITS COLD POCKET OF AIR
ALOFT COMBINED WITH SOME AREAS OF CLEARING/HEATING COULD HELP
TO BLOSSOM SCATTERED SHOWERS AND THUNDERSTORMS. COMPARED TO
STEADIER RAINS TONIGHT AND TUE, THIS WOULD BE MORE OF THE HIT OR
MISS/SHOWERY TYPE OF RAIN CHARACTER. DUE TO THE COLD POCKET OF
AIR ALOFT, FREEZING LEVELS ARE LOWER THAN NORMAL FOR MID MAY AT
AROUND 7.5-8KFT AND MID-LEVEL LAPSE RATES ARE RATHER STEEP AT
AROUND 7 C/KM. MUCAPE VALUES ARE PROGGED TO BE AROUND 1000 J/KG,
ALTHOUGH SHEAR PROFILES DO NOT LOOK NECESSARILY IMPRESSIVE. ANY
THUNDERSTORMS WHICH DO DEVELOP COULD POSE A RISK FOR SMALL SUB-
SEVERE HAIL OR GRAUPEL, BUT SEVERE WEATHER ISN'T ANTICIPATED.
DRYING OUT FOR WEDNESDAY NIGHT, BUT WE COULD HAVE TO WATCH FOR
PATCHY NIGHTTIME FOG GIVEN THE LIKELY DAMP SOILS.
THURSDAY:
THURS LOOKS TO BE THE ONLY RELATIVELY DRY DAY IN THE WORKWEEK,
WITH WEAK SFC RIDGING AND MOSTLY SUNNY TO PARTLY CLOUDY
CONDITIONS. HIGHS COULD REACH MORE SEASONABLE LEVELS IN THE MID
60S TO MID 70S, HOWEVER CLOUDS THEN START TO INCREASE AGAIN FOR
THURS NIGHT.
FRIDAY INTO THE WEEKEND:
PREDICTABILITY IN THE DETAILS THEN DWINDLES WITH PRETTY LARGE
DIFFERENCES IN THE GUIDANCE STILL CONTINUING. WHAT'S REASONABLY
AGREED UPON IS ANOTHER TROUGH OR UPPER LEVEL LOW AGAIN LEADING
TO ANOTHER PERIOD OF UNSETTLED WEATHER, BUT IT REMAINS UNCERTAIN
WHERE SURFACE LOW PRESSURE SETS UP RELATIVE TO SOUTHERN NEW
ENGLAND, EITHER THROUGH THE INTERIOR OR OFFSHORE. IT STANDS TO
BE AGAIN QUITE UNSETTLED, BUT UNTIL THERE'S A BIT MORE
CONSISTENCY, IT'S DIFFICULT TO REALLY PINPOINT MORE SPECIFICS
SHORT OF IT BEING A LIKELY WET WEATHER PATTERN WITH COOLER THAN
NORMAL TEMPS.
AVIATION /05Z TUESDAY THROUGH SATURDAY/
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE:
REST OF TONIGHT: MODERATE CONFIDENCE
IFR/LIFR CONDITIONS ACROSS THE REGION WITH PERIODS OF LIGHT TO
MODERATE SHOWERS. WINDS AT THE SURFACE REMAIN RELATIVELY LIGHT,
HOWEVER, 2KFT WINDS REMAIN AROUND 30-40 KNOTS FROM THE SW, THUS
WIND SHEAR IS LIKELY TONIGHT.
TODAY: MODERATE CONFIDENCE
IFR/LIFR TO START, BUT THERE COULD BE POCKETS OF MVFR
ESPECIALLY LATE IN THE DAY WHEN WINDS TURN MORE SSW. LIGHT TO
MODERATE RAIN EXPECTED MUCH OF THE DAY, TAPERING OFF IN THE LATE
AFTERNOON TO EARLY EVENING. SURFACE WINDS PICK UP SLIGHTLY FROM
THE S TO 10-20 KNOTS WHILE 2KFT WIND DIMINISH TO 20-30 KNOTS
FROM THE S.
TONIGHT: MODERATE CONFIDENCE
IFR/MVFR, EXCEPT ALONG THE SOUTH COAST WHERE LIFR IS POSSIBLE.
RAIN BEGINS TO MOVE OFF SHORE FROM WEST TO EAST WITH ONLY
LINGERING SHOWERS AND DRIZZLE/MIST. WINDS TURN LIGHT SSW.
KBOS TAF...MODERATE CONFIDENCE.
LIFR THROUGH 12Z. SHOULD SEE IMPROVEMENTS TO IFR AFTER 12Z.
THERE COULD BE IMPROVEMENTS TO MVFR LATE IN THE DAY, BUT
CONFIDENCE IS MODERATE AND WILL LIKELY DEPEND ON IF THE WIND
TURNS MORE SOUTHERLY VS SE. PERIODS OF LIGHT TO MODERATE RAIN
EXPECTED THROUGH THE ENTIRE DAY, TAPERING OFF THIS EVENING
KBDL TAF...MODERATE CONFIDENCE.
IFR/LIFR POSSIBLY IMPROVING TO MVFR THIS AFTERNOON. LIGHT TO
MODERATE RAIN EXPECTED THROUGH THE DAY.
OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...
WEDNESDAY: MVFR/IFR CONDITIONS POSSIBLE. CHANCE SHRA.
WEDNESDAY NIGHT: VFR. CHANCE SHRA.
THURSDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. SLIGHT CHANCE
SHRA.
THURSDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE
SHRA.
FRIDAY: MVFR/IFR CONDITIONS POSSIBLE. CHANCE SHRA.
FRIDAY NIGHT: MAINLY VFR, WITH AREAS IFR POSSIBLE. CHANCE SHRA.
SATURDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE SHRA.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT THROUGH TUESDAY NIGHT: HIGH CONFIDENCE.
ENE WINDS THIS AFTERNOON AND TONIGHT WILL GRADUALLY SHIFT TO
MORE OF AN ESE DIRECTION ON TUE. THIS A RESULT OF AN ANOMALOUS
CLOSED UPPER OVER THE OHIO VALLEY GRADUALLY MOVING INTO WESTERN
PA OVER THE NEXT 36 HOURS. WHILE SOME 20+ KNOT WIND GUSTS WILL
BE POSSIBLE AT TIMES, WINDS/SEAS WILL GENERALLY REMAIN BELOW
SMALL CRAFT ADVISORY THRESHOLDS. HOWEVER...PERIODS OF SHOWERS
AND AREAS OF FOG WILL REDUCE VSBYS FOR MARINERS. WINDS TO THEN
TURN SOUTHERLY WITH DECREASING RAIN CHANCES AS WE MOVE INTO
TUESDAY NIGHT.
OUTLOOK /WEDNESDAY NIGHT THROUGH SATURDAY/...
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF
RAIN SHOWERS.
WEDNESDAY NIGHT THROUGH THURSDAY: WINDS LESS THAN 25 KT. SEAS
UP TO 5 FT. SLIGHT CHANCE OF RAIN SHOWERS.
THURSDAY NIGHT THROUGH SATURDAY: WINDS LESS THAN 25 KT. SEAS UP
TO 5 FT. CHANCE OF RAIN SHOWERS.
HYDROLOGY
235 PM UPDATE:
FLOOD WATCH NOW IN EFFECT FOR INTERIOR SOUTHERN NEW ENGLAND
TONIGHT THROUGH TUESDAY. IT MAY NEED TO BE EXPANDED EASTWARD
INTO EASTERN MA/RI IF HIGHER RAINFALL TOTALS MATERIALIZE.
ENTERING INTO A PROLONGED SOGGY WEATHER PATTERN, AS AN UPPER
LEVEL LOW PRESSURE OVER THE OHIO VALLEY DRAWS IN A STREAM OF
RICH SUBTROPICAL MOISTURE NORTHWARD INTO THE MID-ATLANTIC AND
INTO SOUTHERN NEW ENGLAND TONIGHT INTO AT LEAST TUESDAY. THIS
WILL LEAD TO AN ENHANCED PERIOD OF INTEGRATED WATER VAPOR
TRANSPORT AND THE POTENTIAL FOR SLOW-MOVING "TRAINING" RAINFALL
AREAS, WITH UPSLOPE ENHANCEMENT FAVORING HIGHER RAIN TOTALS IN
WESTERN NEW ENGLAND. TWO PERIODS OF STEADY RAIN WITH EMBEDDED
DOWNPOURS ARE EXPECTED: (1) TONIGHT INTO EARLY ON TUESDAY, BEING
MORE FOCUSED INTO WESTERN AND CENTRAL MA AND INTO ALL OF
NORTHERN CT THROUGH THE FIRST HALF OF THE OVERNIGHT, THEN
GRADUALLY SHIFTING EASTWARD INTO EASTERN MA AND RI AS WE MOVE
INTO THE TUESDAY MORNING HOURS. HEAVIEST RAIN TOTALS IN THIS
INITIAL ROUND. (2) TUESDAY LATE- MORNING TO THE AFTERNOON ACROSS
MOST OF SOUTHERN NEW ENGLAND, ALTHOUGH WITH LESSER RAIN TOTALS
THAN THE FIRST ROUND.
THE EXACT AMOUNT OF RAINFALL WE MAY SEE IS STILL A BIT
UNCERTAIN, ALTHOUGH RECENT TRENDS IN HREF LOCALIZED PMM GUIDANCE
AND CMC/ECMWF ENSEMBLE QPF PROBS SUGGEST RAIN TOTALS COULD BE AS
HIGH AS 4 INCHES THRU TUESDAY WHERE SLOW-MOVING HEAVY RAIN
BANDS MATERIALIZE. THE PLACEMENT IS SOMEWHAT MORE CONFIDENT, TO
BE FOCUSED OVER WESTERN MA AND CT, WITH LESSER RAINFALL TOTALS
IN EASTERN MA AND RI. OFFICIAL FORECAST CALLS FOR RAIN TOTALS OF
UP TO 1.5 INCHES THROUGH TUESDAY EARLY EVENING IN EASTERN
MA/RI, WITH 1.75 TO 2.5 INCHES IN LOCATIONS COVERED BY THE FLOOD
WATCH.
INSTANCES OF URBAN AND POOR DRAINAGE STREET FLOODING COULD
DEVELOP IN RESPONSE TO THIS RAIN, ALTHOUGH WE DO NOT EXPECT
FLOODING TO RISE TO SIGNIFICANT LEVELS. RISES ON MOST SMALLER
CREEKS AND LARGER MAINSTEM RIVERS ALSO ARE LIKELY. ALTHOUGH
LATEST RIVER STAGE FORECASTS FROM THE NERFC INDICATE RISES TO
ACTION STAGE, IF HIGHER RAINFALL TOTALS DO DEVELOP, PORTIONS OF
THE CT RIVER COULD SEE RISES TO MINOR FLOOD STAGE PER MMEFS
WATER GUIDANCE OUTPUT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...FLOOD WATCH THROUGH THIS EVENING FOR CTZ002>004.
MA...FLOOD WATCH THROUGH THIS EVENING FOR MAZ002>004-008>012.
RI...NONE.
MARINE...NONE.
SYNOPSIS...LOCONTO
NEAR TERM...LOCONTO
SHORT TERM...LOCONTO
LONG TERM...LOCONTO
AVIATION...KP
MARINE...LOCONTO
HYDROLOGY...LOCONTO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page