228
FXUS61 KBOX 290550
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
150 AM EDT MON JUN 29 2026
WHAT HAS CHANGED
AN EXTREME HEAT WATCH HAS BEEN ISSUED FOR MOST OF SOUTHERN NEW
ENGLAND FROM 10 AM WEDNESDAY THROUGH 8 PM FRIDAY. 06Z AVIATION
DISCUSSION UPDATED.
KEY MESSAGES
- SCATTERED SHOWERS AND A ROGUE THUNDERSTORM OR TWO IN INTERIOR
SOUTHERN NEW ENGLAND DISSIPATE BY SUNDOWN. FOG AND LOW CLOUDS
RETURN TONIGHT INTO EARLY MONDAY MORNING, BUT GIVING WAY TO
MOSTLY SUNNY CONDITIONS AND SUMMERLIKE TEMPERATURES FOR MONDAY
AWAY FROM THE COASTS.
- WARMING TREND THIS WEEK WITH A PERIOD OF DANGEROUS HEAT
LIKELY BY MID TO LATE WEEK.
- ROUNDS OF SHOWERS AND STORMS POSSIBLE MID TO LATE WEEK.
DISCUSSION
KEY MESSAGE 1...SCATTERED SHOWERS AND A ROGUE THUNDERSTORM OR TWO IN
INTERIOR SOUTHERN NEW ENGLAND DISSIPATE BY SUNDOWN. FOG AND LOW
CLOUDS RETURN TONIGHT INTO EARLY MONDAY MORNING, BUT GIVING WAY TO
MOSTLY SUNNY CONDITIONS AND SUMMERLIKE TEMPERATURES FOR MONDAY AWAY
FROM THE COASTS.
WEAK HIGH PRESSURE NEAR THE EASTERN MA COAST WILL CONTINUE TO DRIVE
OUR WEATHER PATTERN THROUGH MONDAY. STARTING TO SEE SCATTERED POP-UP
SHOWERS DEVELOP IN A WEAKLY-UNSTABLE AIRMASS MAINLY IN INTERIOR
SOUTHERN NEW ENGLAND AND ALONG THE SEABREEZE FRONTAL BOUNDARY IN
EASTERN MA AS OF SUNDAY AFTERNOON. WIND FIELDS ALOFT ARE ON THE WEAK
SIDE AND STEERING FLOW LOOKS RATHER ERRATIC/SLOW; WHILE SOME OF
THESE SHOWERS COULD GROW TO PRODUCE A COUPLE LIGHTNING STRIKES, THE
RISK FOR STORMS RISING TO SEVERE WEATHER POTENTIAL IS NIL. THE SLOW-
MOVING, ERRATIC NATURE TO THE SHOWERS MEANS THAT THOSE WHO
EXPERIENCE A DIRECT HIT COULD SEE LOCALLY HEAVY DOWNPOURS. IN
GENERAL THE BEST CHANCE IS ACROSS NORTHERN CT, WESTERN AND CENTRAL
MA AND INTO RI, BUT THERE WILL BE SEVERAL HRS OF DRY WEATHER IN
BETWEEN. EXPECTATION IS THAT THESE SHOWERS/WEAK THUNDERSHOWERS WILL
TEND TO DIMINISH IN COVERAGE AND STRENGTH BY SUNSET.
THE NEXT ITEM TO WATCH FOR IS FOR RE-DEVELOPING LOW CLOUDS AND FOG
TO AGAIN WORK THEIR WAY BACK LANDWARD OVERNIGHT. DAYTIME SATELLITE
IMAGERY SHOWS A CONTINUED MARINE MOIST LAYER IN THE EASTERN MA
WATERS, AND THOUGH THIS HAS TRIED TO RETURN LANDWARD AS WAS THE CASE
YESTERDAY, IT'S BEEN STRUGGLING TO DO SO. IT SEEMS MORE LIKELY THAT
ONCE THE SUN GOES DOWN AND THE BOUNDARY LAYER STARTS TO COOL OFF AND
DECOUPLE THAT FOG AND LOW CLOUDS END UP RETURNING. IT'S A LITTLE
UNCERTAIN EXACTLY WHEN THIS COMES BACK IN, BUT THE ODDS START TO
INCREASE AFTER SUNDOWN AND ESPECIALLY LATE TONIGHT. SO THE POTENTIAL
EXISTS FOR SOME AREAS OF REDUCED VISIBILITY FOR EARLY MONDAY MORNING
COMMUTERS. OTHERWISE, MONDAY ITSELF TURNS OUT TO BE A DRY DAY WITH
FOG DISSIPATING BY MID MORNING AND SEABREEZES KEEPING COASTAL MA
COOLER (LOWER 70S) COMPARED TO MID 80S AWAY FROM THE COAST.
KEY MESSAGE 2... WARMING TREND THIS WEEK WITH A PERIOD OF DANGEROUS
HEAT LIKELY BY MID TO LATE WEEK.
CONFIDENCE CONTINUES TO INCREASE FOR A PERIOD OF EXTREME HEAT MID TO
LATE WEEK. AS A RESULT, AN EXTREME HEAT WATCH HAS BEEN ISSUED FROM
10AM WEDNESDAY TO 8PM FRIDAY.
OVERALL, THE METEOROLOGICAL PICTURE FOR NEXT WEEK IS FAIRLY CLEAR; A
SPRAWLING RIDGE OF HIGH PRESSURE OVER THE TENNESSEE VALLEY MOVES E
OVER THE NORTHEAST BY LATE WEEK. THERE IS LOWER CONFIDENCE IN THE
EVENTUAL TRACK/STRENGTH OF SHORTWAVES RIDING AROUND THE PERIPHERY OF
THE RIDGE BUT THIS WILL BE ADDRESSED IN THE THIRD KEY MESSAGE.
ENSEMBLES CONTINUE TO HIGHLIGHT A BROAD AREA FOR 95+ DEGREE
TEMPERATURES AND HAVE INCREASED THE CHANCES OF >100 TEMPERATURES
GREATEST SIGNAL FOR EXTREME HEAT CONTINUES TO BE IN THE CT AND
MERRIMACK RIVER VALLEYS. HERE, CHANCES FOR HIGHS ABOVE 100 DEGREES
HAVE SURGED TO 50-60 PERCENT WEDNESDAY THROUGH FRIDAY. WEDNESDAY
WILL FEATURE THE LEAST EXTREME ACTUAL AIR TEMPERATURES WITH CLOUD
COVER FROM LINGERING STORMS. EVEN SO, LINGERING BOUNDARY LAYER
MOISTURE SHOULD HELP KEEP DEW POINT TEMPS ABOVE 65 DEGREES, AND WITH
HIGHS IN THE UPPER 90'S APPARENT TEMPERATURES LIKELY SOAR INTO THE
105-110 RANGE FOR MUCH OF THE CWA. THURSDAY AND FRIDAY WILL BE
DOWNRIGHT HOT WITH 925MB TEMPS SOARING TO +30C AS THE CENTER OF THE
RIDGE CRESTS OVER THE NORTHEAST CONUS. WHILE THE INCREASED HEAT MAY
RESULT IN BETTER MIXING AND SLIGHTLY LOWER DEW POINT TEMPERATURES,
APPARENT TEMPERATURES WITH DEW POINTS IN THE LOWER TO MID 60S
COMBINED WITH AIR TEMPERATURES BETWEEN 98 AND 103 DEGREES WILL HAVE
NO ISSUE EXCEEDING HIGH HEAT WARNING CRITERIA IN THE HOTTEST
LOCATIONS. THESE VALUES CONTINUE TO PUSH HEATRISK VALUES TO A MAJOR
(3/4) LEVEL FOR MOST OF THE CWA. IN URBAN AREAS, THE MERRIMACK
VALLEY, AND THE CT RIVER VALLEY FORECAST IMPACTS ARE STILL EXTREME
(4/4), ESPECIALLY THURSDAY AND FRIDAY.
TO REITERATE FROM THE PREVIOUS FORECAST UPDATE, THIS HEAT EVENT WILL
FEATURE EXTREMELY HIGH OVERNIGHT TEMPERATURES OFFERING VERY LITTLE
IN THE WAY OF RELIEF FROM THE EXTREME HEAT. THOSE WITHOUT ACCESS TO
ADEQUATE COOLING AND HYDRATION WILL BE ESPECIALLY VULNERABLE TO
THESE ELEVATED NIGHTTIME TEMPERATURES.
SOME RELIEF MAY ARRIVE BY NEXT WEEKEND AS THE RIDGE ALOFT BREAKS
DOWN. STILL, THE NBM SHOWS TEMPERATURES IN THE LOWER TO MID 90S WITH
850 MB TEMPERATURES AROUND +20C SO HEAT STATEMENTS MAY BE NEEDED
EVEN THROUGH NEXT WEEKEND.
KEY MESSAGE 3...ROUNDS OF SHOWERS AND STORMS POSSIBLE MID TO LATE
WEEK.
DISTURBANCE OVER CENTRAL CANADA WILL ACT AS A RESERVOIR FOR
SHORTWAVES AS THEY MAKE THEIR WAY UP AND OVER THE EXPANSIVE
SUBTROPICAL RIDGE THAT DEVELOPS OVER THE EASTERN CONUS. AS ONE OF
THE SHORTWAVES MOVES INTO NEW ENGLAND TUESDAY NIGHT THERE COULD BE
SOME SHOWERS AND STORMS WITH PERHAPS A MORE ORGANIZED MCS
ORIGINATING FROM SOUTHERN CANADA. CONFIDENCE IS ADMITTEDLY LOW, BUT
INCREASING OVERNIGHT INSTABILITY WOULD PROVIDE PLENTY OF FUEL FOR
ANY STORMS THAT FORM. ONCE THE RIDGE HAS BUILT UP INTO SOUTHERN NEW
ENGLAND FOR WEDNESDAY AND THURSDAY, CHANCES FOR SHOWERS AND STORMS
DROP SIGNIFICANTLY. CHANCES INCREASE FOR THE END OF THE WEEK AS THE
RIDGE BREAKS DOWN. MORE REFINED DETAILS WILL COME INTO THE PICTURE
AS WE GET CLOSER TO BOTH EVENTS. COULD SEE SEVERE WEATHER CLOSER TO
THE END OF THE WEEK AS GUIDANCE SHOWS AN ELEVATED MIXED LAYER
ADVECTING OVER THE REGION THURSDAY NIGHT THROUGH FRIDAY NIGHT. BEST
CHANCE OF SEVERE WEATHER WOULD LIKELY BE AS THE RIDGE BREAKS DOWN
LATER FRIDAY.
AVIATION /06Z MONDAY THROUGH FRIDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE:
THROUGH 12Z...MODERATE CONFIDENCE TOWARDS SOUTH COAST, RI
TERMINALS.
WINDS AT BOS AND TERMINALS INLAND OUTSIDE OF VALLEY AREAS HAVE
MOSTLY SEEN CLEAR SKIES TONIGHT ALONG WITH SW WINDS. THESE WINDS
ARE UNFAVORABLE IN THESE AREAS FOR FOG DEVELOPMENT, AND GIVEN
LATEST SATELLITE AND WEBCAM IMAGERY, CONFIDENCE IN THE
DEVELOPMENT OF IFR/LIFR OVER THESE AREAS HAS DROPPED. GREATEST
RISK FOR IFR/LIFR THIS MORNING APPEARS MOSTLY CONSTRAINED TO THE
IMMEDIATE SOUTH COAST, INCLUDING PARTS OF THE CAPE, AND IN
TYPICAL RADIATIONAL AREAS AND VALLEYS. LIGHT S/SW WINDS, CALM
AT TIMES.
TODAY...HIGH CONFIDENCE.
ANY IFR-LIFR STRATUS AND FOG DISPERSE 12-13Z TO VFR CONDITIONS
THEREAFTER. LIGHT WINDS, WITH SEABREEZES DEVELOPING AT BOS BY
15Z AND PVD BY 16-18Z. THOUGH, BOS COULD SEE ONSHORE WINDS AS
EARLY AS 12Z.
TONIGHT...HIGH CONFIDENCE.
IFR LIKELY TO RETURN WITH FOG OVERNIGHT ACROSS SE MA, RI, CT,
AND THE CAPE AND ISLANDS. WINDS MOSTLY S, REMAINING LIGHT AND
GOING CALM FROM TIME TO TIME.
TUESDAY...HIGH CONFIDENCE.
VFR. WINDS PICK UP IN THE AFTERNOON FROM THE SSW, GUSTING TO 20
KT ACROSS MUCH OF SE MA, RI, AND CT. SHOWERS POSSIBLE TOWARDS
THE LATE EVENING HOURS.
KBOS TERMINAL...MODERATE TO LOW CONFIDENCE IN TAF THROUGH 12Z.
FOG MAY STILL DEVELOP OFFSHORE OF BOS, HOWEVER, IF MORE W WINDS
PREVAIL THROUGH TONIGHT (AS THEY HAVE BEEN), IT COULD BE ENOUGH
TO KEEP IT AT BAY AND OUT OF THE TERMINAL AREA. WENT WITH VFR
THROUGH THE NIGHT DUE TO LOW CONFIDENCE IN SEEING CATEGORY
REDUCTIONS.
KBDL TERMINAL...MODERATE CONFIDENCE IN TAF. RISK FOR MVFR FOG
DEVELOPING BETWEEN 08-09Z.
OUTLOOK /TUESDAY THROUGH FRIDAY/...
TUESDAY THROUGH TUESDAY NIGHT: VFR. BREEZY. CHANCE SHRA, SLIGHT
CHANCE TSRA.
WEDNESDAY: VFR. BREEZY. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.
WEDNESDAY NIGHT THROUGH THURSDAY: VFR. BREEZY.
THURSDAY NIGHT: VFR.
FRIDAY: VFR. BREEZY. SLIGHT 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 NIGHT: HIGH CONFIDENCE.
WINDS AND SEAS REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS,
WITH LIGHT EAST/SOUTHEAST WINDS THROUGH MONDAY NIGHT AND SEAS 3
FT OR LESS ALL WATERS. WINDS NEAR SHORE/PORT ON MONDAY COULD
TURN EAST AROUND 10 KT DUE TO SEA/BAY BREEZES. MAIN ISSUE FOR
MARINERS TONIGHT INTO MONDAY IS FOG AND MIST, WHICH COULD REDUCE
VISIBILITY TO LESS THAN 1 MILE; IT IS LESS CERTAIN IF MIST/FOG
DEVELOPS AGAIN MONDAY EVENING.
OUTLOOK /TUESDAY THROUGH FRIDAY/...
TUESDAY: WINDS LESS THAN 25 KT.
TUESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. SEAS LOCALLY APPROACHING 5 FT. CHANCE OF
RAIN SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
WEDNESDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. SEAS UP TO 5 FT. SLIGHT CHANCE OF RAIN
SHOWERS.
WEDNESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. SEAS UP TO 5 FT. SLIGHT CHANCE OF RAIN
SHOWERS.
THURSDAY: WINDS LESS THAN 25 KT. SEAS UP TO 5 FT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT.
FRIDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...EXTREME HEAT WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY
EVENING FOR CTZ002>004.
MA...EXTREME HEAT WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY
EVENING FOR MAZ002>021-026.
RI...EXTREME HEAT WATCH FROM WEDNESDAY MORNING THROUGH FRIDAY
EVENING FOR RIZ001>007.
MARINE...NONE.
DISCUSSION...LOCONTO/FT
AVIATION...LOCONTO/HRENCECIN/FT
MARINE...LOCONTO/FT
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