454
FXUS61 KBOX 040511
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
111 AM EDT SUN MAY 4 2025
SYNOPSIS
AN UNSETTLED WEATHER PATTERN WITH SHOWERS AT TIMES WILL PERSIST
FOR THE FIRST HALF OF THE UPCOMING WEEK WITH SOMEWHAT COOLER
CONDITIONS. DEPENDING ON HOW MUCH RAIN FALLS EARLY THIS WEEK, WE
COULD SEE RISES TO NEAR OR OVER BANKFULL ON LARGER RIVERS AND
SMALLER STREAMS IN INTERIOR SOUTHERN NEW ENGLAND.
NEAR TERM /THROUGH TODAY/
KEY MESSAGES...
* SCATTERED STRONG TO SEVERE THUNDERSTORMS THROUGH 10 PM
* SEVERE WEATHER THREAT REMAINS NW OF I-95, ESPECIALLY ACROSS
WESTERN/CENTRAL MA
* MAIN SEVERE WEATHER THREAT IS DAMAGING STRAIGHT-LINE WIND
GUSTS
* SECONDARY CONCERNS FOR HAIL AND HEAVY RAIN/URBAN STREET
FLOODING
* SCATTERED SHOWERS AT TIMES OVERNIGHT, BUT NOT A WASHOUT
SEVERE THUNDERSTORM WATCH IN EFFECT FOR ALL OF MA EXCEPT FOR
SOUTHEASTERN MA, AND PORTIONS OF NORTHERN CT UNTIL 8 PM.
LATEST SPC MESOANALYSIS SHOWED SURFACE-BASED CAPE VALUES STILL
IN THE 1,000-1,200 J/KG RANGE. HOWEVER, MIXED-LAYER CAPE VALUES
WERE ONLY ABOUT 250 J/KG. CUMULUS CLOUDS WERE MORE WIDESPREAD.
STILL EXPECTING SCATTERED STRONG TO SEVERE THUNDERSTORMS INTO
THIS EVENING, WITH STORMS WEAKENING AS WE HEAD TOWARDS SUNSET
AND AS STORM MOVE EAST TOWARDS THE COAST.
EFFECTIVE SHEAR WAS ALSO ON THE HIGHER SIDE FOR A TYPICAL SPRING
DAY IN SOUTHERN NEW ENGLAND, ABOUT 40-45 KT ACROSS THE WESTERN
HALF OF OUR REGION. THUS, THE MAIN CONCERN WILL BE DAMAGING
STRAIGHT-LINE WINDS, WITH A LOWER RISK FOR HAIL.
AS FOR TIMING, STILL REALLY LIKE THE LAST FEW RUNS OF THE HRRR
TO DEPICT THE GENERAL TIMING. MADE SOME MINOR CHANGES FROM THE
EARLIER FORECAST. INITIAL ROUND OF THUNDERSTORMS SHOULD DIMINISH
BY MIDNIGHT, WITH ANOTHER ROUND OF SHOWERS POSSIBLE ACROSS
NORTH CENTRAL AND WESTERN MA LATER TONIGHT. STILL NOT RAINING
THIS ENTIRE TIME.
MINOR TWEAKS TO BRING TEMPERATURES BACK IN LINE WITH LATEST
OBSERVATIONS.
BEYOND THE CONVECTION, THE OTHER ISSUE FOR TONIGHT WILL BE THE
EXTENT OF MARINE STRATUS WITH HUMID AIR MOVING OVER THE COOLER
WATERS. WITH MORE OF A SW FLOW OVERNIGHT, NOT THINKING THIS WILL
GET TOO FAR INLAND. THAT IS NOT TO SAY AREAS OF LOW CLOUDS AND
FOG WILL NOT DEVELOP ANYWAY, WILL JUST BE FROM A DIFFERENT
MECHANISM.
SHORT TERM /TONIGHT THROUGH 6 PM MONDAY/
KEY MESSAGES...
* SCATTERED SHOWERS AT TIMES SUNDAY, BUT NOT A WASHOUT
A PERSISTENT FRONT WILL MEANDER BACK AND FORTH ACROSS SOUTHERN
NEW ENGLAND SUNDAY AND SUNDAY NIGHT. THIS WILL KEEP A CHANCE OF
SHOWERS IN THE FORECAST THROUGH SUNDAY NIGHT. STILL NOT RAINING
THIS ENTIRE TIME. HAVE THE GREATEST CONFIDENCE IN RAINFALL FROM
WORCESTER COUNTY WEST IN MA AND ACROSS NORTHERN CT. RAINFALL
CHANCES STILL A LITTLE LESS TOWARDS SOUTHEAST MA. INSTABILITY
STILL APPEARS RATHER LIMITED, SO THINKING THE THREAT OF THUNDER
IS SILL TOO LOW TO INCLUDE IN THE FORECAST.
ABOVE NORMAL TEMPERATURES ANTICIPATED TO CONTINUE, BUT NOT QUITE
AS HIGH AS WHAT WE SAW TODAY DURING SUNDAY.
LONG TERM /MONDAY NIGHT THROUGH SATURDAY/
KEY MESSAGES:
* PROLONGED CLOUDY WEATHER, ONSHORE FLOW AND STEADY RAIN MON
NIGHT THRU TUE NIGHT, WITH EMBEDDED DOWNPOURS POSSIBLE.
HEAVIEST RAIN TOTALS LOOKING MORE LIKELY IN INTERIOR SOUTHERN
NEW ENGLAND.
* RISES ON LARGER RIVERS AND SMALLER STREAMS IN INTERIOR
SOUTHERN NEW ENGLAND POSSIBLE EARLY TO MID NEXT WEEK,
POSSIBLY TO FLOOD STAGE IF HIGHER RAINFALL TOTALS MATERIALIZE.
* FEW SHOWERS POSSIBLE WED BUT NOT AS WIDESPREAD AS MON- TUE.
* DRYING OUT THURS, BUT TURNING UNSETTLED AND QUITE A BIT COOLER
LATE WEEK/WEEKEND?
DETAILS:
MONDAY NIGHT THROUGH TUESDAY NIGHT:
ENSEMBLES CONTINUE TO POINT TO SOUTHERN NEW ENGLAND BEING
POSITIONED BETWEEN A SLOW-MOVING UPPER LOW OVER THE OHIO VALLEY
AND A 1030 MB SFC ANTICYCLONE OVER THE CANADIAN MARITIMES. AN
ENHANCED STREAM OF MOISTURE OF SUBTROPICAL ORIGIN IS PROGGED TO
BE ADVECTED NORTHWARD, ALONG WITH SOUTHEASTERLY ONSHORE.
ALTHOUGH THE TIMING OF RAIN PARTICULARLY IN EASTERN NEW ENGLAND
IS STILL A BIT UNCERTAIN, THE EXPECTED LARGE-SCALE PATTERN IS
ONE THAT FAVORS A PROLONGED PERIOD OF OVERCAST AND RAIN AND
COOLER THAN NORMAL HIGHS/MILDER THAN NORMAL LOWS. THOUGH IT MAY
NOT BE RAINING THE ENTIRE PERIOD OF TIME, CATEGORICAL POPS
REMAIN ADVERTISED GIVEN THIS FORECAST PATTERN, WHICH HAS STAYED
PRETTY CONSISTENT IN RECENT NWP RUNS.
BESIDES THE ABOVE, EVEN THOUGH IT HAS BEEN RATHER DRY, THIS
SLOW- MOVING NORTHERLY- ADVECTING STREAM OF SUBTROPICAL MOISTURE
INFUSING STEADY RAIN WITH EMBEDDED DOWNPOURS AT TIMES IS A
SYNOPTIC AND MESOSCALE ANALOG PATTERN WHICH COULD LEAD TO SOME
AREAS SEEING SOME FAIRLY GOOD HEAVY RAIN FOOTPRINTS FROM
TRAINING OF STEADY RAINS. WHILE THIS IS WELCOME, TOO MUCH OF IT
OVER A LONG PERIOD OF TIME COULD HOWEVER CAUSE HYDROLOGIC
CONCERNS. GREATEST FORECAST QPF IS OVER INTERIOR SOUTHERN NEW
ENGLAND NORTH AND WEST OF I-95, AND THERE ARE QUITE A FEW QPF
BULLSEYES INDICATING POSSIBLE EMBEDDED CONVECTIVE- ENHANCED RAIN
RATES. RIVER STAGE FORECASTS OFF THE MMEFS WEBSITE USING GEFS-
BASED QPF SHOWS SOME RIVERS IN THE CT BASIN RISING CLOSE TO
MINOR FLOOD STAGE EARLY TO MID NEXT WEEK. RISES ON SMALLER
CREEKS AND STREAMS COULD ALSO OCCUR. THOUGH IT'S FAR FROM A
CERTAINTY, IT IS SOMETHING THAT WILL NEED TO BE MONITORED AS WE
MOVE THROUGH EARLY NEXT WEEK.
HIGHS ON TUESDAY IN THE LOWER TO MID 60S, WITH LOWS MONDAY AND
TUESDAY NIGHTS IN THE 40S TO MID/UPPER 50S.
WEDNESDAY:
UPPER LOW THEN BEGINS TO FILL/WEAKEN AND PULL EASTWARD THROUGH
SOUTHERN NEW ENGLAND. THIS MAY BRING SHOWERS OF A MORE
INSTABILITY/COLD-POOL-ALOFT TYPE REGIME WHERE NOT EVERYONE MAY
SEE SHOWERS. TEMPS DO WARM BACK INTO THE UPPER 60S TO LOW 70S
DESPITE A COLD POCKET OF AIR ALOFT, SO THAT MAY ALSO BRING THE
RISK FOR EMBEDDED THUNDERSHOWERS BEFORE THE LOW PULLS FURTHER
EAST.
LATE NEXT WEEK INTO EARLY WEEKEND:
LOOKS AS THOUGH WE DO GET INTO BRIEF RIDGING ALOFT AND DRIER
WEATHER FOR THURSDAY. UNFORTUNATELY LATEST GUIDANCE INDICATES
THIS COULD BE SHORT-LIVED, AS ANOTHER DIGGING SHORTWAVE TROUGH
ALOFT FROM ONTARIO MOVES IN FOR FRI. SOME OF THE INTERNATIONAL
GUIDANCE SOLUTIONS CLOSE THIS LOW OFF INTO AN UPPER LOW WITH
RATHER ANOMALOUSLY COLD LOW LEVEL TEMPS (850 MB TEMPS DOWN TO -2
TO -4C!) FOR FRI INTO SAT. PRECIP CHANCES ARE STILL UNCERTAIN
AND WILL DEPEND ON THE EXACT PLACEMENT OF THIS UPPER FEATURE.
ALTHOUGH WE'VE NOW GONE A TOTAL OF 8 CONSECUTIVE WEEKENDS WITH
MEASURABLE RAIN AT LEAST IN THE BOSTON AREA, AND IT IS POSSIBLE
ANY SHOWERS REMAIN FAR ENOUGH OFFSHORE, IT'S THIS TYPE OF
PATTERN WHICH IS NOT WHAT YOU WANT TO SEE TO BREAK THAT STREAK.
AVIATION /04Z SUNDAY THROUGH THURSDAY/
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE:
THROUGH 12Z SUNDAY: LOW CONFIDENCE.
CEILINGS/VISBYS CURRENTLY ARE IN IFR RANGE IN THE INTERIOR
AFTER YESTERDAY'S THUNDERSTORMS WITH WEAK/CALM WINDS, WITH VFR
OVER THE SOUTHEAST TERMINALS. INTERIOR TERMINALS SHOULD REMAIN
MVFR-IFR THROUGH THE OVERNIGHT. CATEGORIES OVER THE CAPE AND
ISLANDS ARE NOW LESS CERTAIN AS GUID HAS BEEN STUBBORN IN
INDICATING STRATUS AND FOG THAT JUST HASN'T DEVELOPED. TRENDED
THINGS HERE MORE TOWARDS MVFR LEVELS AS WE MOVE THROUGH EARLY
SUN AM. WINDS TO BECOME SOUTHERLY AROUND 5-10 KT.
TODAY: MODERATE CONFIDENCE.
GRADUAL IMPROVEMENT IN CATEGORIES WITH MORE OF AN MVFR-VFR LOOK
IN THE INTERIOR. IF STRATUS DEVELOPS AS FORECAST OVER THE SOUTH
COAST/CAPE AND ISLANDS, WE SHOULD SEE MORE SLOWER/DELAYED
EROSION BUT IT MAY OTHERWISE STAY VFR. RAIN SHOULD HOLD OFF MOST
OF THE DAY, WITH HIT-OR-MISS SHOWERS OVER THE INTERIOR. WINDS
MAINLY SOUTHERLY AROUND 5-10 KT; IT'S A MORE DIFFICULT WIND
FORECAST FOR BOS AND BED WITH POTENTIAL FOR NE WINDS AROUND 5-10
KT TO DEVELOP AFTER 17Z.
TONIGHT AND MONDAY: MODERATE CONFIDENCE.
DETERIORATING CONDITIONS WITH VFR TRENDING TO MVFR-IFR WITH
PERIODS OF SHOWERS, STRATUS AND PERHAPS SOME MIST/FOG TONIGHT,
WITH NOT MUCH OPTIMISM FOR IMPROVEMENT INTO MONDAY. NE WINDS
5-10 KT, WITH SOUTHEAST WINDS AT SIMILAR SPEEDS SOUTHEAST NEW
ENGLAND.
KBOS TAF...MODERATE CONFIDENCE. IFR CEILINGS TO TREND VFR BY
EARLY SUNDAY MORNING. TOUGH WIND FORECAST WITH POSSIBLE PERIOD
OF NE WINDS DEVELOPING AFTER 17Z.
KBDL TAF...MODERATE CONFIDENCE.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY THROUGH MONDAY NIGHT: MVFR/IFR CONDITIONS POSSIBLE.
BREEZY. SHRA LIKELY.
TUESDAY: MAINLY MVFR, WITH AREAS IFR POSSIBLE. SHRA, ISOLATED
TSRA.
TUESDAY NIGHT: MVFR/IFR CONDITIONS POSSIBLE. SHRA, ISOLATED
TSRA.
WEDNESDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE SHRA,
ISOLATED TSRA.
WEDNESDAY NIGHT: VFR. SLIGHT CHANCE SHRA.
THURSDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE SHRA.
MARINE
FORECASTER CONFIDENCE LEVELS:
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
MODERATE CONFIDENCE.
A FRONT WILL REMAIN NEARLY STATIONARY NORTH AND WEST OF THE
WATERS INTO SUNDAY, THEN PERHAPS REACH THE EASTERN WATERS SUNDAY
NIGHT. THIS WILL MAINTAIN A RISK FOR SHOWERS INTO SUNDAY NIGHT.
GUSTY SW WINDS TODAY SHOULD DIMINISH TONIGHT, AND NOT BECOME AS
GUSTY SUNDAY. SMALL CRAFT ADVISORIES CONTINUE AS PREVIOUSLY
POSTED. AREAS OF FOG MAY RESULT IN POCKETS OF VISIBILITY LESS
THAN 1 NM FOR A TIME LATE TONIGHT INTO SUNDAY MORNING.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
CHANCE OF RAIN SHOWERS.
MONDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
TUESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. RAIN SHOWERS
LIKELY, ISOLATED THUNDERSTORMS.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. RAIN
SHOWERS, ISOLATED THUNDERSTORMS.
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. CHANCE OF
RAIN SHOWERS.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 11 AM EDT THIS MORNING FOR
ANZ254>256.
SYNOPSIS...BELK/FT
NEAR TERM...BELK
SHORT TERM...BELK
LONG TERM...LOCONTO
AVIATION...FRANK/LOCONTO
MARINE...BELK/FT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page