259
FXUS61 KBOX 132347
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
747 PM EDT MON JUL 13 2026
WHAT HAS CHANGED
NO MAJOR CHANGES TO THE CURRENT FORECAST.
KEY MESSAGES
- HIGH HEAT AND HUMIDITY RETURN TUESDAY AND WEDNESDAY. HEAT
ADVISORIES IN EFFECT TUESDAY MORNING THROUGH WEDNESDAY
MORNING. GUSTY SOUTHWEST WINDS TUESDAY AND TUESDAY NIGHT.
- PERIODS OF UNSETTLED WEATHER POSSIBLE LATER THIS
WEEK.
DISCUSSION
KEY MESSAGE 1...HIGH HEAT AND HUMIDITY RETURN TUESDAY AND WEDNESDAY.
HEAT ADVISORIES IN EFFECT TUESDAY MORNING THROUGH WEDNESDAY MORNING.
GUSTY SOUTHWEST WINDS TUESDAY AND TUESDAY NIGHT.
MARGINAL INSTABILITY AND DAYTIME HEATING HAVE ALLOWING A FEW
ISOLATED SHOWERS TO DEVELOP ACROSS WESTERN MA THIS AFTERNOON. EXPECT
A FEW SPOT SHOWERS OR PERHAPS A WEAK STORM THROUGH THE EVENING.
AN STRONG RIDGE ALOFT WILL ADVECT HIGHER HEIGHTS AND ANOMALOUSLY
WARM TEMPERATURES ALOFT INTO THE REGION TUESDAY INTO WEDNESDAY. 925
MB TEMPERATURES RISE TO +26-28C AND WITH EFFICIENTLY MIXED GUSTY
SOUTHWESTERLY TO WESTERLY WINDS. THIS WILL ALLOW TEMPERATURES TO
RISE WELL INTO THE 90S BOTH DAYS FOR MUCH OF SOUTHERN NEW ENGLAND.
SOUTHWESTERLY FLOW WILL ALSO HELP ADVECT IN A PLUME OF HIGHER
DEWPOINT AIR WITH VALUES IN THE UPPER 60S TO NEAR 70. THE ADDED
HUMIDITY FACTOR WILL MAKE TEMPERATURES FEEL MORE LIKE UPPER 90S AND
LOW 100S. RELIEF FROM THE HEAT WILL BE MINIMAL WITH OVERNIGHT
TEMPERATURES IN THE MID 70S TO NEAR 80 TUESDAY NIGHT INTO WEDNESDAY
AM. THIS HAS ELEVATED HEATRISK INTO THE MAJOR CATEGORY LIKELY DUE TO
TWO DAYS OF ABNORMAL HEAT AND HUMIDITY WITH LITTLE OVERNIGHT RELIEF.
THIS CAN IMPACT A LARGER POPULATION OF PEOPLE INCLUDING THOSE WHO
ARE HEAT SENSITIVE AND ALSO THOSE WHO DO NOT USE CAUTION WITH THE
HEAT. ON TUESDAY, THE CT VALLEY AND EASTERN MA HAVE THE HIGHER
PROBABILITY FOR TEMPERATURES IN THE UPPER 90S/HEAT INDEX IN LOW
100S. AS A TROUGH SHIFTS SOUTH INTO WEDNESDAY THE HEAT SHIFTS TOWARD
THE SOUTH COAST WHILE STILL REMAINING HOT ACROSS OTHER PARTS OF
SOUTHERN NEW ENGLAND. HEAT ADVISORIES WILL BE IN EFFECT TUESDAY
THROUGH WEDNESDAY MORNING FOR MUCH OF SOUTHERN NEW ENGLAND WITH THE
EXCEPTION OF THE CAPE AND ISLANDS AND BERKSHIRES. CAPE COD WAS
BORDERLINE FOR WEDNESDAY, BUT KEPT THEM OUT DUE TO THE LOWER
CONFIDENCE IN HOW MANY LOCATIONS WILL HIT 90 AND ONSHORE SW WINDS.
IF CONFIDENCE INCREASES THEY MAY BE ADDED TO THE EXISTING ADVISORY.
THIS IS A GROWING RISK FOR GUSTY SOUTHWESTERLY WINDS TUESDAY INTO
TUESDAY NIGHT. MODEL SOUNDINGS SHOW SUFFICIENT MIXING DOWN OF HIGHER
WINDS ALOFT; HOWEVER, THERE IS UNCERTAINTY IN HOW STRONG THE WINDS
ARE ALOFT AND TO WHAT DEGREE THEY GET MIXED TO THE SURFACE. IT IS
LIKELY WE WILL SEE GUSTS INCREASE LATE AFTERNOON WITH GUSTS 20-30
MPH. IT CAN'T BE RULED OUT FOR LOCALIZED HIGHER GUSTS 35-40 MPH
ACROSS THE SOUTH SHORE AND CAPE/ISLANDS, LATE AFTERNOON THROUGH
TUESDAY NIGHT AS A LLJ STRENGTHENS OVER THE REGION.
KEY MESSAGE 2...PERIODS OF UNSETTLED WEATHER POSSIBLE LATER THIS
WEEK.
THE PERIOD OF ELEVATED HEAT COMES TO AN END FOR THE LATTER HALF OF
THE WEEK AS THE UPPER LEVEL RIDGE STARTS TO SAG MORE SOUTH OF THE
REGION. 850 MB TEMPERATURES START TO FALL BACK BELOW 20C AND BY
FRIDAY FALL TO BETWEEN 10-15C ACROSS SOUTHERN NEW ENGLAND. WITH THE
RIDGE'S INFLUENCE OVER THE REGION WEAKENING, A STRENGTHENING UPPER
LEVEL TROUGH MOVING ACROSS QUEBEC WILL MOVE IN DURING THIS PERIOD AS
WELL. GUIDANCE HAS CONTINUED TO SHOW THE POSSIBILITY OF SHORTWAVES
MOVING ALONG THE BASE OF THE TROUGH OVER SOUTHERN NEW ENGLAND
STARTING AS EARLY AS WEDNESDAY NIGHT, CONTINUING INTO THE WEEKEND.
THESE COULD BRING THE RISK FOR MORE UNSETTLED CONDITIONS TO ROUND
OUT THE WEEK, ESPECIALLY FOR THE WEEKEND.
CSU ML PROBS ARE HINTING AT THE RISK FOR DAMAGING WINDS AND POSSIBLE
SEVERE HAIL FOR WEDNESDAY INTO THURSDAY, HOWEVER, THESE
PROBABILITIES REMAIN LOW AT THIS TIME. THIS WOULD BE ASSOCIATED WITH
AN INCOMING COLD FRONT THAT MAY BRING AN INCREASED RISK OF SHOWERS
AND STORMS, THOUGH COVERAGE IS LOOKING MORE ISOLATED BASED ON THE
LATEST GUIDANCE.
AVIATION /00Z TUESDAY THROUGH SATURDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT...HIGH CONFIDENCE IN TRENDS.
VFR. GUSTY SW WINDS TO 20-25 KT MAY CONTINUE INTO THE EARLY PART
OF THE OVERNIGHT PERIOD FOR SOME TERMINALS. THERE IS STILL A
CHANCE THAT SOME AREAS MAY NOT DECOUPLE OVERNIGHT AND WINDS MAY
REMAIN GUSTY. LATEST GUIDANCE IS MORE SUPPORTIVE OF THIS OUTCOME
TOWARDS CAPE AND ISLAND TERMINALS. OTHER TERMINALS ARE EXPECTED
TO BE BREEZY OVERNIGHT WITH WINDS GENERALLY AROUND 10 KT
SUSTAINED (WITH THE EXCEPTION OF BDL). CONFIDENCE IN LLWS
OCCURRING TONIGHT REMAINS QUITE LOW AT THIS TIME.
TUESDAY...HIGH CONFIDENCE.
VFR. SW WINDS 10-20 KTS WITH GUSTS 20-30 KTS.
TUESDAY NIGHT...HIGH CONFIDENCE.
VFR. CONTINUED SW WINDS AT 10-15 KT, GUSTING BETWEEN 20-30 KT
ESPECIALLY PRIOR TO 06Z. GUIDANCE IS FAVORING THE DEVELOPMENT OF
A LLJ TOWARDS THE SOUTH COAST, INCLUDING THE CAPE AND ISLANDS IN
THE EVENING HOURS TUESDAY, WITH SOME SHOWING WINDS REACHING 45-50
KT AT 950 MB BY 00Z. GIVEN THE PRESENCE OF THIS JET, LLWS WILL
LIKELY BE AN ISSUE HEADING INTO THE EVENING/OVERNIGHT PERIOD FOR
CAPE AND ISLAND TERMINALS.
KBOS TERMINAL...HIGH CONFIDENCE.
KBDL TERMINAL...HIGH CONFIDENCE.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY: VFR. BREEZY.
WEDNESDAY NIGHT: VFR.
THURSDAY THROUGH FRIDAY: VFR. BREEZY.
FRIDAY NIGHT: VFR. SLIGHT CHANCE SHRA.
SATURDAY: 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 WEDNESDAY...HIGH CONFIDENCE.
GUSTY SOUTHWEST WINDS EXPECTED TUESDAY AND TUESDAY NIGHT. SCA
HAVE BEEN ISSUED TUESDAY, WITH GUSTY SOUTHWEST WINDS 25-30 KTS
ACROSS THE SOUTHERN AND EASTERN WATERS. A SCA HAS NOW BEEN ADDED
FOR BOSTON HARBOR AND MASS BAY FOR A PERIOD OF GUSTS 25 KTS LATE
TUESDAY AFTERNOON THROUGH THE EVENING. SEAS WILL BE QUITE
CHOPPY TUESDAY INTO WEDNESDAY MORNING WITH WAVE HEIGHTS 5-8 FT
POSSIBLE ACROSS THE SOUTHERN OCEAN WATERS AND 3-5 FT ALONG THE
COASTAL WATERS, INCLUDING VINEYARD AND NANTUCKET SOUNDS.
AGITATED SEAS WILL RAISE THE RISK TO "MODERATE" FOR RIP
CURRENTS TUESDAY AND WEDNESDAY. THE SOUTH COAST AND SOUTH-
FACING BEACHES OF MARTHA'S VINEYARD AND NANTUCKET HAVE THE
HIGHER RISK FOR DUE TO PROLONGED GUSTY SOUTHWESTERLY FLOW.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 25 KT. LOCAL ROUGH SEAS.
WEDNESDAY NIGHT THROUGH FRIDAY: WINDS LESS THAN 25 KT. SEAS
LOCALLY APPROACHING 5 FT.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS.
SATURDAY: WINDS LESS THAN 25 KT. CHANCE OF RAIN SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...HEAT ADVISORY FROM 11 AM TUESDAY TO 8 PM EDT WEDNESDAY FOR
CTZ002>004.
MA...HEAT ADVISORY FROM 11 AM TUESDAY TO 8 PM EDT WEDNESDAY FOR
MAZ003>007-010>021-026.
AIR QUALITY ALERT FROM 11 AM TO 11 PM EDT TUESDAY FOR
MAZ017>024.
RI...HEAT ADVISORY FROM 11 AM TUESDAY TO 8 PM EDT WEDNESDAY FOR
RIZ001>007.
AIR QUALITY ALERT FROM 11 AM TO 11 PM EDT TUESDAY FOR
RIZ001>008.
MARINE...SMALL CRAFT ADVISORY FROM 4 PM TO 11 PM EDT TUESDAY FOR ANZ230-
231-250-251.
SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 11 AM EDT WEDNESDAY
FOR ANZ232-233-235-237-254>256.
SMALL CRAFT ADVISORY FROM NOON TUESDAY TO 5 AM EDT WEDNESDAY
FOR ANZ234.
DISCUSSION...HRENCECIN/MENSCH
AVIATION...HRENCECIN/MENSCH
MARINE...HRENCECIN/MENSCH
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page