332
FXUS61 KBOX 300516
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
116 AM EDT THU APR 30 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES.
KEY MESSAGES
- COASTAL CLOUDS, DRIZZLE, AND FOG GIVE WAY TO WIDESPREAD
BENEFICIAL RAINFALL TONIGHT INTO THURSDAY.
- COOLER AND MAINLY DRY THIS WEEKEND THEN MILDER NEXT WEEK WITH
A FEW SHOWERS.
DISCUSSION
KEY MESSAGE 1...COASTAL CLOUDS, DRIZZLE, AND FOG GIVE WAY TO
WIDESPREAD BENEFICIAL RAINFALL TONIGHT INTO THURSDAY.
LOW CLOUD DECK FINALLY ERODED A BIT THANKS TO DAYTIME HEATING
AND WAS CONFINED TO AREAS NEAR THE IMMEDIATE COAST, ALTHOUGH
WE'RE SEEING SOME SUBSTANTIAL BREAKS IN CLOUD COVER ESPECIALLY
NEAR CAPE COD AND ISLANDS. CLOUD DECK SHOULD BEGIN TO EXPAND
WESTWARD AGAIN THIS EVENING AS WE LOSE DAYTIME HEATING AND
BOUNDARY LAYER COOLS, AND DEEPENING MARINE LAYER SHOULD PROMOTE
PATCHY FOG AND DRIZZLE ALONG COAST. FARTHER INLAND, MOSTLY CLEAR
SKIES WILL PERSIST WITH INCREASING MID AND HIGH CLOUDS EARLY
TONIGHT.
WE'RE STILL LOOKING AT TWO AREAS OF SHOWERS TONIGHT INTO THURSDAY.
FIRST IS LATER THIS AFTERNOON AND EVENING ACROSS EASTERN MA IN
ASSOCIATION WITH SURFACE TROUGH FROM OFFSHORE LOW. SHOWERS WILL THEN
BECOME MORE WIDESPREAD LATER TONIGHT INTO THURSDAY MORNING AS
WE COME UNDER BROAD LARGER SCALE LIFT AHEAD OF UPPER TROUGH (AS
SEEN IN MODEL Q-VECTOR FIELDS) AND PRIMARY LOW TRACKING THROUGH
THE ST. LAWRENCE VALLEY. SECONDARY LOW TRACKING FROM MID
ATLANTIC HAS TRENDED WEAKER SINCE YESTERDAY SO BETWEEN THAT AND
THE SPEED OF THE SYSTEM OVERALL RAINFALL WILL BE LESS, ON THE
ORDER OF AROUND 0.5" FOR MOST, BUT STILL MUCH NEEDED GIVEN
RECENT RAINFALL DEPARTURES.
GUIDANCE DOES SHOW SOME MARGINAL INSTABILITY ON THE EDGE OF THE DRY
SLOT THAT LIFTS THROUGH SOUTHERN NEW ENGLAND THURSDAY MORNING,
FOCUSED NEAR CAPE COD AND ISLANDS, BUT MORESO OFFSHORE. IT'S
POSSIBLE WE SEE SOME ADDITIONAL SHOWERS OR EVEN A THUNDERSTORM
POP UP IN THOSE AREAS BUT THAT IS CONDITIONAL ON SEEING BETTER
INSTABILITY.
KEY MESSAGE 2...COOLER AND MAINLY DRY THIS WEEKEND THEN TURNING
MILDER EARLY NEXT WEEK WITH A FEW SHOWERS.
AMPLIFIED PATTERN OVER THE WEEKEND SHOULD FEATURE A BUILDING RIDGE
OF HIGH PRESSURE OVER CENTRAL CANADA WHICH TRAPS A CLOSED UPPER LOW
OVER SOUTHERN ONTARIO. AS MENTIONED BEFORE, SOUTHERN NEW ENGLAND
SHOULD BE FAR ENOUGH REMOVED FROM COLDEST AIR ALOFT TO KEEP US
MOSTLY DRY, ESPECIALLY GIVEN W/NW FLOW, BUT PATTERN CERTAINLY FAVORS
DIURNAL CLOUDS AND PERHAPS A FEW AFTERNOON SPRINKLES OVER WEEKEND.
WE'RE ALSO WATCHING A WEAK LOW ALSO PASSING OFFSHORE THAT COULD COME
CLOSE ENOUGH TO BRING A FEW SHOWERS TO PARTS OF EASTERN MA AND RI
LATER SATURDAY INTO SUNDAY, BUT RIGHT NOW ANY RAINFALL LOOKS TO BE
FAIRLY LIGHT AND MAY END UP BEING MORE FOCUSED NEAR CAPE COD AND THE
ISLANDS OR EVEN OFFSHORE.
PATTERN RELAXES A BIT EARLY NEXT WEEK AS CLOSED LOW LIFTS FARTHER
NORTH, BUT WE REMAIN UNDER BROAD CYCLONIC FLOW ALOFT. EVENTUALLY
LONGER RANGE GUIDANCE SHOWS CLOSED LOW SETTING UP NEAR UPPER GREAT
LAKES, PUTTING US IN SW FLOW ALOFT. THIS COULD END UP BRINGING
MORE MOISTURE INTO REGION BY TUESDAY/WEDNESDAY AS WEAK FRONT
APPROACHES RESULTING IN SCATTERED SHOWERS. TEMPERATURES SHOULD
RETURN TO MORE TYPICAL LEVELS FOR EARLY MAY HOWEVER.
AVIATION /06Z THURSDAY THROUGH MONDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE: MODERATE CONFIDENCE DUE TO TIMING OF FLIGHT
CATEGORIES.
WIDESPREAD -SHRA THRU 14Z WITH IFR CEILINGS/VISIBILITIES.
SHOWERS COME TO AN END AROUND MIDDAY TODAY WITH GRADUAL
IMPROVEMENT TO MVFR CEILINGS, AND POSSIBLY VFR LATER IN DAY WITH
THE EXCEPTION OF CAPE COD AND ISLANDS.
KBOS TERMINAL...MODERATE CONFIDENCE. REDUCED CONFIDENCE IN THE
END TIME OF IFR/LIFR THIS AFTERNOON.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /FRIDAY THROUGH MONDAY/...
FRIDAY: VFR. BREEZY.
FRIDAY NIGHT: VFR.
SATURDAY: VFR. SLIGHT CHANCE SHRA.
SATURDAY NIGHT: VFR. CHANCE SHRA.
SUNDAY: VFR. BREEZY. SLIGHT CHANCE SHRA.
SUNDAY NIGHT: VFR.
MONDAY: VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
HIGH CONFIDENCE THROUGH THE END OF THE WEEK.
PRESSURE GRADIENT BETWEEN SLOW-MOVING LOW PRESSURE SE OF THE 40/70
BENCHMARK AND HIGH PRESSURE OVER THE CANADIAN MARITIMES KEEPS E/NE
WINDS IN PLAY THROUGH THE END OF THE WEEK.
MAIN ISSUE WILL BE THE LONG FETCH OF NE WINDS RESULTING IN ROUGH
SEAS OF 5 TO 8 FEET ON OUTER WATERS THROUGH THU WHERE SCA REMAINS
POSTED. AREAS OF FOG WILL PERSIST THROUGH THU ALONG WITH SHOWERS,
ESPECIALLY LATER TONIGHT THROUGH EARLY THU AFTERNOON.
OUTLOOK /FRIDAY THROUGH MONDAY/...
FRIDAY THROUGH FRIDAY NIGHT: WINDS LESS THAN 25 KT. SEAS UP TO
5 FT.
SATURDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
SUNDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
SLIGHT CHANCE OF RAIN SHOWERS.
SUNDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT.
MONDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 AM EDT FRIDAY FOR ANZ250.
SMALL CRAFT ADVISORY UNTIL 8 PM EDT FRIDAY FOR ANZ254>256.
DISCUSSION...JWD
AVIATION...FT
MARINE...JWD
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