028
FXUS61 KBOX 042319
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
719 PM EDT TUE AUG 4 2026
WHAT HAS CHANGED
CONFIDENCE CONTINUES TO INCREASE FOR THE REGION TO SEE A STRETCH
OF WARM AND HUMID CONDITIONS FOR LATE WEEK INTO THE WEEKEND.
KEY MESSAGES
- WEAK LOW PRESSURE BRINGS SOME CLOUDS AND A LOW RISK FOR A
SHOWER EARLY WEDNESDAY ACROSS MARTHA'S VINEYARD AND NANTUCKET
- INCREASING HEAT AND HUMIDITY ACROSS MUCH OF SOUTHERN NEW
ENGLAND, ALONG WITH DAILY AFTERNOON POP-UP THUNDERSTORMS FROM
THURSDAY THROUGH THIS WEEKEND. A WIDESPREAD WASHOUT IS NOT
ANTICIPATED AT THIS TIME.
DISCUSSION
KEY MESSAGE 1...WEAK LOW PRESSURE BRINGS SOME CLOUDS AND A LOW
RISK FOR A SHOWER EARLY WEDNESDAY ACROSS MARTHA'S VINEYARD AND
NANTUCKET
OVERALL A PRETTY QUIET NIGHT, WEATHER-WISE, IS EXPECTED FOR MOST
OF THE REGION. WEAK HIGH PRESSURE OVER CT AND WESTERN MA WILL
RESULT IN MOSTLY CLEAR SKIES WITH SOME PATCHY VALLEY FOG PERHAPS
FORMING. LOW TEMPERATURES WILL BE SEASONABLE, GENERALLY THE
LOWER 60S. THE ONLY OTHER FEATURE ON THE WEATHER MAP IS A VERY
WEAK LOW PRESSURE SEVERAL HUNDRED MILES OF SOUTHERN NEW ENGLAND.
THIS WILL TRACK NORTHEAST, AND ALTHOUGH IT WILL PASS SOUTH OF
NANTUCKET LATE TONITE/EARLY WEDNESDAY MORNING, MOISTURE AROUND
THE LOW MAY BE ENOUGH TO PRODUCE A PERIOD OF LOW CLOUDS AS FAR
NORTH AS CAPE COD. LOW (LESS THAN 25%) CHANCE OF A LIGHT SHOWER
IS ALSO POSSIBLE ACROSS MARTHA'S VINEYARD AND NANTUCKET BETWEEN
ROUGHLY 4A-8A.
KEY MESSAGE 2...INCREASING HEAT AND HUMIDITY ACROSS MUCH OF SOUTHERN
NEW ENGLAND, ALONG WITH DAILY AFTERNOON POP-UP THUNDERSTORMS
FROM THURSDAY THROUGH THIS WEEKEND. A WIDESPREAD WASHOUT IS NOT
ANTICIPATED AT THIS TIME.
THERE IS INCREASING CONFIDENCE IN A PROLONGED PERIOD OF MIDSUMMER
WARMTH AND HUMIDITY, ALONG WITH DAILY CHANCES FOR AFTERNOON POP-UP
THUNDERSTORMS FROM THURSDAY THROUGH THE UPCOMING WEEKEND. HOWEVER, A
WIDESPREAD WASHOUT IS NOT ANTICIPATED. GIVEN THE ABUNDANT RAINFALL
EARLIER THIS WEEK, ANY STORMS CAPABLE OF PRODUCING HEAVY DOWNPOURS
COULD LEAD TO LOCALIZED INSTANCES OF FLASH FLOODING. THIS IS
REFLECTED IN THE WPC MARGINAL RISK (LEVEL 1 OF 4) FOR EXCESSIVE
RAINFALL ACROSS WESTERN NEW ENGLAND ON THURSDAY AND ALL OF SOUTHERN
NEW ENGLAND ON FRIDAY.
BERMUDA HIGH PRESSURE DEVELOPS THIS WEEK AND REMAINS ANCHORED OVER
THE WESTERN ATLANTIC THROUGH THE REMAINDER OF THE FORECAST PERIOD.
WITH PERSISTENT SOUTHWESTERLY FLOW, EXPECT ABOVE-NORMAL TEMPERATURES
ALONG WITH INCREASING HUMIDITY. WHILE TEMPERATURES WILL BE ABOVE
CLIMATOLOGICAL NORMALS, THEY ARE NOT PARTICULARLY UNUSUAL FOR EARLY
AUGUST. HIGH TEMPERATURES FROM THURSDAY THROUGH SUNDAY SHOULD CLIMB
WELL INTO THE UPPER 80S AND LOWER 90S, WHILE DEWPOINTS RISE INTO THE
LOWER TO MIDDLE 70S. THIS COMBINATION WILL RESULT IN HEAT INDEX
VALUES OF 95 TO 100 DEGREES. IF CURRENT TRENDS CONTINUE, HEAT
ADVISORIES MAY BE NEEDED FOR PORTIONS OF THE REGION THURSDAY AND
FRIDAY, AND PERHAPS SATURDAY AS WELL. ONE UNCERTAINTY IS THE DEGREE
OF AFTERNOON CLOUD COVER AND THUNDERSTORM DEVELOPMENT, WHICH COULD
TEMPER TEMPERATURES SOMEWHAT. THIS WILL BE MONITORED OVER THE COMING
DAYS.
REGARDING THUNDERSTORM CHANCES, THE OVERALL SYNOPTIC PATTERN
FEATURES THE BERMUDA HIGH OVER THE WESTERN ATLANTIC WITH A MID-LEVEL
RIDGE EXTENDING ACROSS THE NORTHEAST. EMBEDDED SHORTWAVE
DISTURBANCES RIDING THROUGH THE FLOW SHOULD PROVIDE ENOUGH LIFT TO
INITIATE SCATTERED AFTERNOON AND EVENING THUNDERSTORMS FROM THURSDAY
THROUGH SUNDAY. ALTHOUGH DEEP-LAYER SHEAR REMAINS WEAK, INSTABILITY
WILL BE PLENTIFUL, WITH FORECAST CAPE VALUES GENERALLY BETWEEN 1,500
AND 2,000 J/KG. AS A RESULT, STORMS SHOULD REMAIN LARGELY PULSE-TYPE
AND DISORGANIZED RATHER THAN ORGANIZED SEVERE CONVECTION. BUFKIT
SOUNDINGS DEPICT TALL, SKINNY CAPE PROFILES, SUGGESTING EFFICIENT
WARM-RAIN PROCESSES AND THE POTENTIAL FOR LOCALLY HEAVY RAINFALL.
PWAT VALUES AROUND 1.7 INCHES FURTHER SUPPORT THE THREAT OF
TORRENTIAL DOWNPOURS. IN ADDITION TO LOCALIZED FLOODING, GUSTY WINDS
AND FREQUENT LIGHTNING WILL BE THE PRIMARY HAZARDS.
THAT SAID, NOT EVERY COMMUNITY WILL EXPERIENCE THUNDERSTORMS EACH
DAY. MANY LOCATIONS WILL REMAIN DRY, SO THERE IS NO REASON TO CANCEL
OUTDOOR PLANS AT THIS POINT. THE DETAILS REGARDING STORM COVERAGE
AND PLACEMENT WILL BECOME CLEARER ONCE THE CONVECTION-ALLOWING
GUIDANCE COMES INTO RANGE OVER THE NEXT COUPLE OF DAYS.
AVIATION /00Z WEDNESDAY THROUGH SUNDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
00Z TAF UPDATE:
HIGH CONFIDENCE.
WEAK HIGH PRESSURE OVERHEAD TONIGHT WILL RESULT IN GENERALLY
CLEAR SKIES AND LIGHT WINDS FOR MOST OF THE REGION. COULD SEE
SOME PATCHY VALLEY FOG, BUT NOT EXPECTING ANY AT TAF LOCATIONS.
SLIGHTLY DIFFERENT OUTLOOK FOR THE CAPE AND ISLANDS. WEAK LOW
PRESSURE WILL PASS SOUTH OF ACK LATE TONIGHT, BUT COULD BE CLOSE
ENOUGH TO RESULT IN SOME LOWER CEILINGS. HAVE SOME MVFR FOR FMH
AND HYA, AND IFR AT ACK. COULD EVEN SEE -SHRA AT ACK EARLY IN
THE MORNING. ANY LOW CEILINGS SHOULD CLEAR OUT BY 14Z.
OTHERWISE WEDNESDAY WILL FEATURE VFR. BELIEVE A SEA BREEZE WILL
AGAIN FORM. ALTHOUGH AN ISOLATED SHOWER CAN'T BE RULED OUT
ACROSS THE WESTERN INTERIOR. INCREASING MOISTURE WEDNESDAY NIGHT
SHOULD RESULT IN MVFR/IFR CONDITIONS AS LOW CLOUDS, ESPECIALLY
ACROSS THE SOUTHERN COASTAL AREAS. MAY ALSO SEE A FEW -SHRA
DEVELOP PRIOR TO 12Z THURSDAY ACROSS CT.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. CHANCE
SHRA, CHANCE TSRA.
THURSDAY NIGHT: VFR.
FRIDAY: VFR. BREEZY. CHANCE SHRA, SLIGHT CHANCE TSRA.
FRIDAY NIGHT: VFR. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.
SATURDAY: VFR. BREEZY. CHANCE SHRA, CHANCE TSRA.
SATURDAY NIGHT THROUGH SUNDAY: VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THE NEED FOR A SMALL CRAFT ADVISORY ACROSS THE OUTER SOUTHERN
WATERS WILL COME TO AN END BY EARLY THIS EVENING AS SEAS SLOWLY
SUBSIDE TO BELOW 5FT. OTHERWISE A "BERMUDA HIGH" WILL BECOME
FIRMLY ENTRENCHED OFF THE EASTERN SEA BOARD RESULTING IN AN
EXTENDED PERIOD OF SW WINDS.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY: WINDS LESS THAN 25 KT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT.
FRIDAY: WINDS LESS THAN 25 KT.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. SLIGHT CHANCE OF RAIN SHOWERS.
SATURDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS.
SUNDAY: WINDS LESS THAN 25 KT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...HIGH RISK FOR RIP CURRENTS UNTIL 9 PM EDT THIS EVENING FOR MAZ020-
023-024.
RI...HIGH RISK FOR RIP CURRENTS UNTIL 9 PM EDT THIS EVENING FOR
RIZ006>008.
MARINE...NONE.
DISCUSSION...DOOLEY/NASH
AVIATION...DOOLEY/NASH
MARINE...DOOLEY/NASH
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