871
FXUS61 KBOX 300649
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
249 AM EDT SUN AUG 30 2026
WHAT HAS CHANGED
GAINING CONFIDENCE IN THE TIMING DETAILS FOR RAINFALL TONIGHT
INTO MONDAY.
KEY MESSAGES
- WARMER WITH INCREASING CLOUDS. RAIN CHANCES RETURN LATE TODAY
INTO TONIGHT FOR CT, RI AND SOUTHEAST MA.
- BACKDOOR COLD FRONT MONDAY BRINGS ONSHORE FLOW, DECREASED
CLOUD COVER AND LOWER TEMPERATURES.
- UNSETTLED TUESDAY THROUGH THURSDAY WITH SEVERAL OPPORTUNITIES
FOR SHOWERS AND THUNDERSTORMS, WITH A CHANCE FOR SOME TO
BECOME STRONG IN WESTERN MA AND CT. TIMING WHICH DAYS MAY HAVE
BETTER STORM CHANCES IS STILL UNCERTAIN.
DISCUSSION
KEY MESSAGE 1...WARMER WITH INCREASING CLOUDS. RAIN CHANCES
RETURN LATE TODAY INTO TONIGHT FOR CT, RI AND SOUTHEAST MA.
LATEST GUIDANCE CONTINUED TO INDICATED A WEAK LOW PRESSURE
MOVING CLOSE TO THE REGION, EMPHASIZING RAINFALL CHANCES
GENERALLY SOUTH OF I-90 TONIGHT. IT'S WORTH NOTING, THOUGH,
THAT SHOWERS DO REMAIN POSSIBLE ACROSS ALL OF SOUTHERN NEW
ENGLAND STARTING IN THE LATE EVENING HOURS. THERE'S A LOW CHANCE
FOR SOME EMBEDDED THUNDER, BUT THAT IS GENERALLY RELEGATED TO
THE SOUTH COAST AND THE SOUTHERN WATERS. NOT ANTICIPATING A
WASHOUT. HIGHER CONFIDENCE THAT SHOWERY CONDITIONS CONTINUE
OVERNIGHT SUNDAY TOWARDS THE SOUTH COAST, CLEARING OUT HEADING
INTO MONDAY MORNING.
KEY MESSAGE 2...BACKDOOR COLD FRONT MONDAY BRINGS ONSHORE FLOW,
DECREASED CLOUD COVER AND LOWER TEMPERATURES.
STILL SOME QUESTION AS TO HOW QUICKLY A BACKDOOR FRONT WILL MAKE
IT ACROSS SOUTHERN NEW ENGLAND LATE TONIGHT INTO MONDAY. LATEST
GUIDANCE SUITE CONTINUED TO FAVOR A FASTER TIMING, LEAVING
SOUTHERN NEW ENGLAND ON THE DRIER, ALBEIT COOLER, SIDE. MAY NOT
BE QUITE AS MUCH OF A TEMPERATURE DIFFERENCE WELL AWAY FROM
EASTERN MA
CLOUD COVER THEN INCREASES MONDAY NIGHT WITH RAINFALL CHANCES
INCREASING FROM WEST TO EAST, ESPECIALLY AFTER MIDNIGHT.
KEY MESSAGE 3...UNSETTLED TUESDAY THROUGH THURSDAY WITH SEVERAL
OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS, WITH A CHANCE FOR
SOME TO BECOME STRONG IN WESTERN MA AND CT. TIMING WHICH DAYS
MAY HAVE BETTER STORM CHANCES IS STILL UNCERTAIN.
TUESDAY THROUGH THURSDAY LOOKS MORE ACTIVE/UNSETTLED, AS THE
BACKDOOR FRONTAL BOUNDARY STALLS FROM SW TO NE THROUGH NY STATE
AND THE NORTHEAST FRINGE OF A SUBSTANTIAL HEAT RIDGE CENTERED
OVER THE OHIO VALLEY BY TUESDAY TRIES TO BUILD INTO THE
NORTHERN MID ATLANTIC AND PERHAPS INTO A SMALL PORTION OF
SOUTHERN NEW ENGLAND. THIS PLACES SOUTHERN NEW ENGLAND BETWEEN
A MORE STABLE AND SEASONABLE AIRMASS TO THE NORTHEAST AND A
WARM/HOT, HUMID AND CONDITIONALLY UNSTABLE AIRMASS TO OUR
SOUTHWEST.
ABOVE THIS STALLED SURFACE BOUNDARY LIES A BELT OF STRONG NW
FLOW ALOFT (E.G. 300 MB WINDS APPROACHING 100 KT), WHICH TENDS
TO FAVOR SHORTWAVE ENERGY IMPULSES MOVING SE ALONG THE STALLED
FRONT. SEVERAL OPPORTUNITIES FOR SHOWERS AND THUNDERSTORMS SEEM
LIKELY DURING THIS PERIOD, BUT THE DETAILS OF WHICH ARE
UNCERTAIN. THOSE HINGE ON THE EXACT PLACEMENT/EVOLUTION OF THE
FRONTAL BOUNDARY, IF WE CAN TAP INTO THE MORE UNSTABLE AIR TO
OUR SOUTHWEST, AND THE TIMING OF SHORTWAVES IN THE STRONG NW
FLOW ALOFT.
MACHINE-LEARNING GUIDANCE FROM THE GEFS AND COLORADO STATE SHOW
SOME SEVERE WEATHER POTENTIAL FOR OUR WESTERN/SOUTHWEST COUNTIES
IN THIS PERIOD, AND SPC HIGHLIGHTS A SMALL SLIVER OF WESTERN
HAMPDEN COUNTY AND WESTERN/CENTRAL HARTFORD COUNTY IN A 15%
PROBABILITY FOR SEVERE WEATHER FOR WEDNESDAY, UNCOMMON FOR WHAT
IS A DAY-5 FORECAST. AM SKEPTICAL WE GET ENTRENCHED INTO THE
MORE UNSTABLE AIR TO OUR SOUTHWEST BUT THE BEST POTENTIAL FOR
DOING SO WOULD MORE LIKELY BE SOUTH AND WEST OF WORCESTER.
SOMETHING THAT WE'LL NEED TO MONITOR AS WE GET INTO THE
MESOSCALE MODEL RANGE.
GAINING CONFIDENCE IN A PERIOD OF SHOWERS LATE MONDAY NIGHT INTO
TUESDAY EVENING. THERE COULD BE A BRIEF BREAK LATE TUESDAY
NIGHT INTO EARLY WEDNESDAY. ANOTHER ROUND OF SHOWERS IS POSSIBLE
FROM WEDNESDAY AFTERNOON INTO THURSDAY. WILL HAVE TO SEE IF THIS
TIMING PERSISTS WITH LATER FORECASTS, BUT THIS IS THE BEST
ESTIMATE AT THIS TIME.
AVIATION /06Z SUNDAY THROUGH THURSDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TODAY...HIGH CONFIDENCE.
WINDS SHIFT TO THE SW EARLY THIS MORNING, THEN INCREASE TO
AROUND 10 KT. SOME OCCASIONAL GUSTS LOOK POSSIBLE THIS
AFTERNOON, PARTICULARLY TOWARDS THE CAPE AND ISLAND TERMINALS.
TONIGHT...MODERATE CONFIDENCE.
VFR, THOUGH SHOWERS ARE POSSIBLE ACROSS CT/RI/SE MA AND INTO THE
CAPE AND ISLANDS. PERIODS OF MVFR VISIBILITIES IN ANY SHRA THAT
DEVELOP ARE POSSIBLE, THOUGH CONFIDENCE IN TIMING AND LOCATION IS
LOW AT THIS TIME. WINDS SHIFT MORE NW HEADING INTO MONDAY
MORNING, THOUGH REMAIN LIGHT.
MONDAY...HIGH CONFIDENCE.
VFR. LIGHT N TO NE WINDS.
KBOS TERMINAL...HIGH CONFIDENCE.
KBDL TERMINAL...HIGH CONFIDENCE.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY NIGHT: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. CHANCE
SHRA.
TUESDAY: MVFR/IFR CONDITIONS POSSIBLE. SHRA, SLIGHT CHANCE
TSRA.
TUESDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE
SHRA, SLIGHT CHANCE TSRA.
WEDNESDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE SHRA.
WEDNESDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SHRA
LIKELY, SLIGHT CHANCE TSRA.
THURSDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. CHANCE SHRA,
SLIGHT CHANCE TSRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH MONDAY...HIGH CONFIDENCE.
HIGH PRESSURE CONTINUES TO MOVE OFFSHORE TODAY, RESULTING IN SW
WINDS ACROSS THE WATERS. COULD SEE A FEW GUSTS UP TO 25 KT. AT
THIS TIME, NOT THINKING THIS WILL BE PERSISTENT OR WIDESPREAD
ENOUGH TO WARRANT ANY SMALL CRAFT ADVISORIES, BUT WILL NEED TO
MONITOR THIS ASPECT OF THE FORECAST, PARTICULARLY ACROSS THE
SOUTHERN COASTAL BAYS AND SOUNDS.
DRY TODAY, WITH A RISK FOR SOME SHOWERS AND POSSIBLE
THUNDERSTORMS TONIGHT. A BACKDOOR FRONT SHOULD CROSS THE WATERS
FROM N TO S TONIGHT INTO MONDAY MORNING.
OUTLOOK /MONDAY NIGHT THROUGH THURSDAY/...
MONDAY NIGHT THROUGH TUESDAY: WINDS LESS THAN 25 KT. CHANCE OF
RAIN SHOWERS.
TUESDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF RAIN SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
WEDNESDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT. SLIGHT
CHANCE OF RAIN SHOWERS.
WEDNESDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS
APPROACHING 5 FT. CHANCE OF RAIN SHOWERS.
THURSDAY: WINDS LESS THAN 25 KT. AREAS OF SEAS APPROACHING
5 FT. CHANCE OF RAIN SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
DISCUSSION...BELK/LOCONTO
AVIATION...BELK/LOCONTO
MARINE...BELK/LOCONTO
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