266
FXUS61 KBOX 292257
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
657 PM EDT MON JUN 29 2026
WHAT HAS CHANGED
THE EXTREME HEAT WATCH HAS BEEN EXTENDED INTO THE FOURTH OF
JULY.
KEY MESSAGES
- DANGEROUSLY HIGH HEAT INDICES ARE LOOKING LIKELY WEDNESDAY
THROUGH FRIDAY AND POSSIBLY LINGERING INTO THE FOURTH OF JULY.
- SHOWERS AND THUNDERSTORMS POSSIBLE LATER THIS WEEK.
DISCUSSION
KEY MESSAGE 1...DANGEROUSLY HIGH HEAT INDICES ARE LOOKING LIKELY
WEDNESDAY THROUGH FRIDAY AND POSSIBLY LINGERING INTO THE FOURTH
OF JULY.
AN ANOMALOUSLY STRONG UPPER LEVEL RIDGE WILL BE CENTERED OVER
THE LOWER OHIO VALLEY THROUGH THE NORTHERN MID-ATLANTIC THROUGH
THE REST OF THE WORKWEEK, THEN BEGINNING TO FLATTEN INTO THE
FOURTH OF JULY HOLIDAY. THE PRESENCE OF THIS RIDGE WILL ADVECT
THE WARMEST AIRMASS WE'VE SEEN TO THIS POINT IN THE SUMMER BY A
LARGE MARGIN, WITH 850 MB TEMPS RUNNING AROUND +22 TO +24C
WEDNESDAY THROUGH FRIDAY. THESE VALUES ARE SIMILAR/ONLY SLIGHTLY
COOLER ON THE FOURTH OF JULY, RUNNING AROUND +18 TO +21C.
WE'VE OPTED TO EXTEND THE EXTREME HEAT WATCH INTO THE FOURTH OF
JULY WITH THIS FORECAST PACKAGE. THIS IS NOT WITHOUT UNCERTAINTY
THOUGH, AS THE RIDGE STARTS TO FLATTEN ON THE FOURTH OF JULY,
WHICH OPENS THE DOOR FOR CLOUD COVER AND POSSIBLE THUNDERSTORM
OPPORTUNITIES TO COOL US DOWN. STILL, WITH A NUMBER OF OUTDOOR
ACTIVITIES AHEAD GIVEN THE HOLIDAY, WE DIDN'T WANT TO GIVE THE
IMPRESSION THAT THE DANGEROUSLY HIGH HEAT INDICES ARE TOTALLY
OUT OF THE QUESTION. LATEST ENSEMBLES SEEM TO BE TILTING IN
FAVOR OF A CONTINUATION OF HIGH HEAT AND HUMIDITY ON THE FOURTH
OF JULY.
PEAK OF THE HEAT AND HUMIDITY FALLS ON WEDNESDAY THROUGH FRIDAY,
AND THE MOST OPPRESSIVE OF THE DAYS CURRENTLY LOOKS TO BE
THURSDAY. AIR TEMPERATURES IN THE MID 90S TO AROUND 100 WITH
ELEVATED DEWPOINTS LEADING TO HIGH HUMIDITY LEVELS, WILL FAVOR
HEAT INDICES IN THE 105 TO 110 DEGREE RANGE WITH POTENTIAL FOR
EVEN HIGHER VALUES. WHAT IS IMPORTANT TO KEEP IN MIND IS THAT
THIS ISN'T JUST FOR ONE DAY: THAT WE'LL BE DEALING WITH THIS
LEVEL OF HEAT AND HUMIDITY FOR 3 TO POTENTIALLY AS MANY AS 4
DAYS, WITH MUGGY NIGHTTIME LOWS IN THE MID 70S ADDING TO THE
ACCUMULATION OF HEAT STRESS JUSTIFIES THE WATCH. EVEN IF HEAT
INDICES FALL SHORT OF EXTREME HEAT WARNING CRITERION ON THE
FOURTH OF JULY, HEAT INDICES SHOULD STILL BE ENOUGH TO CAUSE
POTENTIAL FOR HEAT- RELATED ILLNESSES.
KEY MESSAGE 2...SHOWERS AND THUNDERSTORMS POSSIBLE LATER THIS
WEEK.
SOUTHERN NEW ENGLAND IS EXPECTED TO REMAIN EAST OF A MID LEVEL
RIDGE AXIS INTO THE MIDDLE PART OF THIS WEEK. THIS WILL KEEP US
IN A RELATIVE NORTHWEST FLOW ALOFT. MEANWHILE, THE INCREASING
HEAT AND HUMIDITY CLOSER TO THE GROUND WILL RESULT IN SOME
MODEST POTENTIAL FOR SHOWERS AND THUNDERSTORMS AT TIMES.
CURRENT THINKING FOR TUESDAY IS THAT SHOWERS AND THUNDERSTORMS
SHOULD ARRIVE FROM THE NORTHWEST LATE IN THE DAY. THIS COULD BE
CLOSE TO SUNSET, WHICH WILL DAMPEN THE RISK FOR STRONGER
THUNDERSTORMS. MOST UNSTABLE CAPE VALUES OF 500-800 J/KG ARE
ANTICIPATED WITH 40+ KT OF EFFECTIVE SHEAR. THUS, THINKING THE
GREATEST RISK FOR THE STRONGEST CONVECTION WILL BE TO OUR
NORTHWEST.
ANY SHOWERS SHOULD MOVE OFF TO OUR EAST OR NORTH BY WEDNESDAY AS
A WARM FRONT MOVES INTO NORTHERN NEW ENGLAND AND A HIGH
PRESSURE OVER THE CENTRAL APPALACHIANS TAKES MORE CONTROL OF OUR
WEATHER. CANNOT DISMISS THE IDEA OF A FEW POP-UP AFTERNOON OR
EVENING SHOWERS AND THUNDERSTORMS WEDNESDAY THROUGH FRIDAY, BUT
MOST OF THIS TIME SHOULD BE DRY. A FRONT SAGGING SOUTH LATER
FRIDAY INTO SATURDAY SHOULD BE OUR NEXT CHANCE FOR SHOWERS AND
THUNDERSTORMS. THOSE DETAILS WILL COME INTO BETTER FOCUS WITH
LATER FORECASTS THIS WEEK.
AVIATION /00Z TUESDAY THROUGH SATURDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
00Z TAF UPDATE:
TONIGHT: HIGH CONFIDENCE.
VFR FOR MOST, ALTHOUGH IFR-LIFR MIST/STRATUS DEVELOPS ALONG THE
SOUTH COASTAL WATERS BY AROUND 03Z AND SPREADS NORTHWARD INTO
CAPE COD, THE ISLANDS AND PERHAPS AS FAR NORTH AS PVD. LIGHT
SE/S WINDS, BUT BECOMING CALM AT TIMES OVERNIGHT.
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.
TUESDAY NIGHT...HIGH CONFIDENCE.
VFR. LIGHT SOUTHWEST WINDS.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF. POTENTIAL FOR SEABREEZE
BY 15Z IF SW WINDS REMAIN LIGHT ENOUGH, BUT WOULD PROBABLY TURN
SW BY LATE IN THE DAY.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY THROUGH THURSDAY NIGHT: VFR. BREEZY.
FRIDAY: VFR. BREEZY. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.
FRIDAY NIGHT: VFR. SLIGHT CHANCE SHRA.
INDEPENDENCE DAY: VFR. CHANCE SHRA, CHANCE TSRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH TUESDAY NIGHT: HIGH CONFIDENCE.
RELATIVELY LIGHT WINDS AND SEAS EXPECTED THROUGH AT LEAST
TUESDAY MORNING. INCREASING SOUTHWEST WINDS AHEAD OF A COLD
FRONT COULD RESULT IN SOME GUSTS NEAR 25 KT TUESDAY AFTERNOON
INTO TUESDAY NIGHT. AREAS OF FOG RETURN TONIGHT, RESULTING IN
POOR VISIBILITY LESS THAN 1 MILE AT TIMES.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. SEAS UP TO 5 FT.
WEDNESDAY NIGHT: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS
WITH GUSTS UP TO 25 KT. SEAS UP TO 5 FT. CHANCE OF RAIN
SHOWERS.
THURSDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 25 KT. SEAS UP TO 5 FT.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. AREAS OF SEAS
APPROACHING 5 FT.
FRIDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
INDEPENDENCE DAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...AIR QUALITY ALERT FROM 11 AM TO 11 PM EDT TUESDAY FOR CTZ002.
EXTREME HEAT WATCH FROM WEDNESDAY MORNING THROUGH SATURDAY
EVENING FOR CTZ002>004.
MA...EXTREME HEAT WATCH FROM WEDNESDAY MORNING THROUGH SATURDAY
EVENING FOR MAZ002>021-026.
RI...EXTREME HEAT WATCH FROM WEDNESDAY MORNING THROUGH SATURDAY
EVENING FOR RIZ001>007.
MARINE...NONE.
DISCUSSION...BELK/LOCONTO
AVIATION...BELK/LOCONTO
MARINE...BELK/LOCONTO
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