505
FXUS61 KBOX 291117
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
717 AM EDT MON JUN 29 2026
WHAT HAS CHANGED
NO SIGNIFICANT CHANGES.
KEY MESSAGES
- WARMING TREND TAKES HOLD. CONFIDENCE CONTINUES TO INCREASE IN
DANGEROUS HEAT WEDNESDAY THROUGH FRIDAY.
- SHOWERS AND THUNDERSTORMS POSSIBLE MID TO LATE WEEK.
DISCUSSION
KEY MESSAGE 1...WARMING TREND TAKES HOLD. CONFIDENCE CONTINUES TO
INCREASE IN DANGEROUS HEAT WEDNESDAY THROUGH FRIDAY.
MORNING FOG THAT DEVELOPED ALONG THE SOUTH COAST AND PARTS OF THE
CAPE (PLUS MARTHA'S VINEYARD) SHOULD ERODE AWAY AFTER SUNRISE THIS
MORNING. HIGH PRESSURE CONTINUES TO EXERT ITS INFLUENCE OVER THE
REGION AHEAD OF A STRENGTHENING UPPER LEVEL RIDGE TO OUR WEST. HIGHS
TODAY CLIMB INTO THE MID TO UPPER 80S FOR MOST, STAYING A BIT COOLER
TOWARDS THE COASTS AND OVER THE CAPE AND ISLANDS.
NOT MUCH HAS CHANGED IN THE OVERALL TRENDS OF THE FORECAST
OVERNIGHT. A STRONG UPPER LEVEL RIDGE CONTINUES BUILDING IN FROM THE
WEST, SHIFTING OVER THE NORTHEAST CONUS LATE THIS WEEK. ENSEMBLES
REMAIN IN STRONG AGREEMENT THAT WE WILL SEE TEMPERATURES OVER 90-95
STARTING WEDNESDAY AND CONTINUING THROUGH THE REST OF THE WEEK. THE
HIGHEST PROBABILITIES OF TEMPERATURES REACHING AND/OR EXCEEDING 100F
OVER URBAN AREAS AND THE RIVER VALLEYS, ESPECIALLY ON THURSDAY, ALSO
CONTINUE TO INCREASE. GEFS PROBABILITIES OF 100F+ FOR THURSDAY
AFTERNOON RANGE NOW REACH UP TO 60-70 PERCENT WITH CANADIAN ENSEMBLE
PROBABILITIES PEAKING SLIGHTLY HIGHER AT UP TO 80 PERCENT. ALL
ENSEMBLES ARE IN PRETTY GOOD AGREEMENT HAVING THE HIGHEST
PROBABILITIES IN THE CT VALLEY AND TOWARDS THE BOSTON METRO UP INTO
THE MERRIMACK VALLEY. THE CONTINUED OVERALL CONSENSUS ACROSS THE
DIFFERENT GUIDANCE SUITE AIDS IN INCREASING CONFIDENCE IN THE RISK
FOR THIS DANGEROUS HEAT OVERALL. MEAN 850 MB TEMPERATURES ACROSS THE
ENSEMBLES CONTINUE TO REACH 20-24C DURING THIS STRETCH, AND 925 MB
TEMPERATURES IN THE DETERMINISTIC GUIDANCE CONTINUE TO KEY IN ON 25C
TEMPERATURES AND HIGHER, EVEN TO 30C. NOTABLY, THE GFS HAS THE
HIGHEST 925 MB TEMPERATURES CENTERED OVER CT AND EASTERN MA. THIS IS
ALL BEFORE DEW POINTS AND OVERALL MOISTURE ARE BEING TAKEN INTO
ACCOUNT. CONSIDERING DEW POINTS ARE EXPECTED TO BE IN THE UPPER 60S
AND EVEN INTO THE LOW 70S, HEAT INDICES TO 110F ARE NOT OUT OF THE
QUESTION FOR SOME AREAS. AN EXTREME HEAT WATCH WILL BE IN EFFECT
FROM WEDNESDAY MORNING THROUGH FRIDAY EVENING FOR THIS REASON, ALONG
WITH LIMITED OVERNIGHT TEMPERATURE RECOVERY. MAJOR (3/4) TO EXTREME
(4/4) HEATRISK IMPACTS ARE VERY POSSIBLE, WITH THE EXTREME IMPACTS
MORE LIKELY OVER URBAN AREAS AND IN RIVER VALLEYS.
AS BRIEFLY HIGHLIGHTED ABOVE, ANOTHER ISSUE WITH THESE HIGH DAYTIME
TEMPERATURES IS THAT NOT MUCH RELIEF IS EXPECTED OVERNIGHT. NBM HAS
LOW PROBABILITIES FOR TEMPERATURES GETTING BELOW 70F OVERNIGHT
BETWEEN WEDNESDAY AND FRIDAY, GENERALLY BELOW 10 PERCENT ACROSS MUCH
OF SOUTHERN NEW ENGLAND. IT ALSO HAS PROBABILITIES BETWEEN 75-90
PERCENT FOR EARLY THURSDAY MORNING AND EARLY FRIDAY MORNING
TEMPERATURES IN EASTERN MA (ESPECIALLY BOSTON) REMAINING ABOVE 75F
FROM OVERNIGHT. THE OTHER ENSEMBLES ARE EQUALLY PESSIMISTIC WITH
RECOVERY; GEFS, ECMWF ENS, AND THE CANADIAN ENSEMBLE ARE ALL
ESSENTIALLY SHOWING MAXIMUM PROBABILITIES THAT THE REGION STAYS AT
OR ABOVE 70F OVERNIGHT BETWEEN WEDNESDAY AND FRIDAY NIGHT.
KEY MESSAGE 2...SHOWERS AND THUNDERSTORMS POSSIBLE MID TO LATE WEEK.
SHORTWAVES ORIGINATING FROM A DISTURBANCE IN CENTRAL CANADA WILL
TRACK EASTWARD AND MAY IMPACT SOUTHERN NEW ENGLAND BEFORE THE UPPER
LEVEL RIDGE FULLY BUILDS UP OVER THE REGION. THESE WAVES WILL TRACK
ALONG THE EASTERN PERIPHERY, WITH ONE LIKELY ARRIVING TUESDAY NIGHT
AND ANOTHER ARRIVING ONCE THE RIDGE STARTS BREAKING DOWN TOWARDS THE
END OF THE WEEK. SHOWERS AND STORMS ARE A POSSIBILITY TUESDAY NIGHT,
AND SOME GUIDANCE IS HINTING AT INCREASED INSTABILITY OVERNIGHT THAT
COULD FUEL ANY STORMS THAT DO DEVELOP. CSU ML PROBS AND OTHER
GUIDANCE AREN'T SHOWING MUCH IN THE WAY OF A SEVERE SIGNAL AT THIS
TIME, BUT WE WILL CONTINUE TO MONITOR FOR ANY RISK THAT COULD
DEVELOP. WITH THE RIDGE FULLY BUILD UP OVER THE REGION WEDNESDAY AND
THURSDAY, CHANCES FOR ANY SHOWERS OR STORMS DROP SIGNIFICANTLY.
CHANCES RETURN AS THE RIDGE BREAKS DOWN TOWARDS THE END OF THE WEEK,
AND THE RISK FOR SEVERE WEATHER COULD BE HIGHER TOWARDS FRIDAY AND
SATURDAY. CIPS ANALOGS ARE HINTING AT IT PARTICULARLY FOR WESTERN
AND CENTRAL MA. MORE REFINED DETAILS WILL COME INTO THE PICTURE AS
WE GET CLOSER TO BOTH EVENTS.
AVIATION /12Z MONDAY THROUGH FRIDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
12Z TAF UPDATE:
TODAY...HIGH CONFIDENCE.
MOST AREAS HAVE LIFTED TO VFR, WITH SOME SCATTERED AREAS OF
BCFG LINGERING THRU 13Z ALONG THE SOUTH COAST/CAPE/ISLAND
TERMINALS. LIGHT WINDS, WITH SEABREEZES DEVELOPING AT BOS BY 15Z
AND PVD BY 16-18Z. THOUGH, BOS COULD SEE ONSHORE WINDS AS EARLY
AS 12-13Z.
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...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY NIGHT: VFR. BREEZY. CHANCE SHRA.
WEDNESDAY THROUGH WEDNESDAY NIGHT: VFR. BREEZY. SLIGHT CHANCE
SHRA.
THURSDAY THROUGH THURSDAY NIGHT: VFR. BREEZY.
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 TUESDAY: HIGH CONFIDENCE.
WINDS AND SEAS REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS,
WITH LIGHT EAST/SOUTHEAST WINDS THROUGH TONIGHT AND SEAS 3 FT
OR LESS ALL WATERS. WINDS NEAR SHORE/PORT TODAY COULD TURN EAST
AROUND 10 KT DUE TO SEA/BAY BREEZES. FOG THAT ERODES THROUGH THE
DAY TODAY MAY MAKE A RETURN TONIGHT. WINDS TUESDAY COULD GUST TO
25 KT OCCASIONALLY IN THE AFTERNOON OVER THE SOUTHERN COASTAL
AND EASTERN OUTER WATERS.
OUTLOOK /TUESDAY NIGHT THROUGH FRIDAY/...
TUESDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. CHANCE OF
RAIN SHOWERS.
WEDNESDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. SEAS UP TO 5 FT. SLIGHT CHANCE OF RAIN
SHOWERS.
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 20 KT. AREAS OF SEAS APPROACHING 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.
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...HRENCECIN
AVIATION...MCMINN
MARINE...HRENCECIN
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page