069
FXUS61 KBOX 210637
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
237 AM EDT MON JUL 21 2025
SYNOPSIS
IT WILL TURN COOLER AND MUCH LESS HUMID MONDAY AND TUESDAY.
A WARMING TREND BEGINS WEDNESDAY, WITH HEAT AND HUMIDITY
RETURNING FOR THURSDAY AND ESPECIALLY FRIDAY WHEN HIGHS MAY
REACH 95 TO 100 DEGREES RESULTING IN DANGEROUS HEAT INDICES.
SUMMER HEAT AND HUMIDITY MAY PERSIST INTO NEXT WEEKEND...ALTHOUGH
PROBABLY NOT TO THE MAGNITUDE OF WHAT WE ARE EXPECTING FOR
FRIDAY. DRY WEATHER FOR MUCH OF THE WORK WEEK, BUT THE RISK FOR
A FEW SHOWERS AND THUNDERSTORMS BEGINS FRIDAY AND CONTINUES INTO
NEXT WEEKEND.
NEAR TERM /THROUGH TODAY/
230 AM UPDATE:
KEY MESSAGE:
* SUNNY, A LITTLE BREEZY AND MUCH LESS HUMID. HIGHS 70S TO LOW 80S.
DETAILS:
SURFACE COLD FRONT HAS PASSED INTO THE SOUTHEAST OFFSHORE WATERS,
WITH NORTHERLY WINDS IN PLACE AND DEWPOINTS BEGINNING TO FALL INTO
THE 60S. THE REAL AIRMASS CHANGE IS STILL WORKING ITS WAY SOUTH
THROUGH CENTRAL VT/CENTRAL NH, WHERE DEWPOINT TEMPS ARE COMMONLY IN
THE MID 50S.
REALLY NICE DAY SHAPING UP FOR SOUTHERN NEW ENGLAND AS RIDGING
ASSOCIATED WITH A 1020 MB SFC CANADIAN-ORIGIN ANTICYCLONE BUILDS
INTO THE REGION. THIS WILL SUPPLY A FEW FAIR WEATHER CLOUDINESS BUT
FULL SUN AND MUCH LOWER HUMIDITY LEVELS AS DEWPOINTS PLUMMETT INTO
THE 50S AND EVEN SOME UPPER 40S TOWARD LATER IN THE DAY. UNTIL THEN,
COMBO OF RATHER DEEP MIXING TO 800 MB AND 3-HOURLY PRESSURE RISES
AROUND 3-4 MB WILL SUPPORT NORTHERLY BREEZES, WITH SPEEDS 10-15 MPH
AND DEVELOPING GUSTS UP TO 25 MPH PICKING UP AROUND MID TO LATE
MORNING. OVERALL A MOSTLY SUNNY, BREEZY AND MUCH LESS HUMID DAY
IDEAL FOR OUTDOOR PLANS, WITH HIGHS IN THE 70S TO NEAR 80.
SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/
230 AM UPDATE:
KEY MESSAGES:
* CLEAR SKIES/LIGHT WINDS TONIGHT AND AGAIN ON TUE NIGHT,
COOLER LOWS UPPER 40S - MID 50S.
* SUNNY TUE, COOLER SEABREEZES NEAR COASTS, HIGHS MID 70S-LOW 80S.
DETAILS:
1020 MB HIGH PRESSURE CONTINUES TO BUILD SOUTHWARD INTO NEW ENGLAND
TONIGHT. CLEAR SKIES AND A DECOUPLING BOUNDARY LAYER AFTER SUNDOWN
TONIGHT SHOULD FAVOR STRONG RADIATIONAL COOLING, WITH 925 MB TEMPS
DROPPING TO A SEASONABLY-COOL +11-13C. TONIGHT IS WITHOUT QUESTION
ONE OF THOSE NIGHTS WHERE YOU CAN GIVE YOUR A/C OR CENTRAL AIR UNITS
A BREAK AND OPEN THOSE WINDOWS. MOS GUIDANCE SHOULD DO PRETTY WELL
TONIGHT, WITH LOWS IN THE UPPER 40S TO THE MID 50S (URBAN AND
COASTAL AREAS). COOLEST LOWS IN THE LOCATIONS WHICH TYPICALLY
RADIATE WELL.
COOLER START FOR A TYPICAL LATE-JULY DAY ON TUESDAY, ALTHOUGH TEMPS
SHOULD RECOVER PRETTY WELL UNDER FULL SUN WITH COMFORTABLE
HUMIDITIES. STILL SHOULD SEE HIGHS RECOVER BACK INTO THE 70S TO LOW
80S, THOUGH A SEABREEZE ON BOTH EASTERN AND SOUTHERN COASTS
OCCURRING PRETTY EARLY IN THE DAY SHOULD KEEP HIGHS IN THE MID 70S.
FOR TUESDAY EVENING...STILL ANOTHER STRONG RADIATIONAL COOLING NIGHT
AS HIGH PRESSURE SLIDES OFFSHORE. BUT AS IT DOES SO, DEWPOINTS START
TO RISE INTO THE LOWER TO MID 50S. COULD LEAD TO PATCHY FOG AS
COOLING TEMPS THRU RADIATIONAL EFFECTS ARE MET WITH RISING DEWPOINTS
BUT CONFIDENCE IS LOW ON DEVELOPMENT. LOWS IN THE 50S, STILL A
PRETTY NICE EVENING OVERALL.
LONG TERM /WEDNESDAY THROUGH SUNDAY/
KEY MESSAGES:
* TURNING WARMER AND INCREASINGLY MORE HUMID WED THRU FRI.
* ELEVATED HEAT INDICES THU (MID 90S), WITH DANGEROUS HEAT INDICES
(100-105+) BY FRI. HEAT HEADLINES POSSIBLE.
* DRY WEATHER THRU THURS, BUT A COLD FRONT FRI SUPPORTS A POTENTIAL
FOR THUNDERSTORMS, ALTHOUGH IT IS UNCLEAR ON HOW STRONG ANY STORMS
MAY BECOME.
* HUMID WEEKEND WITH STALLED FRONTAL BOUNDARY AROUND, WHICH COULD
FAVOR OPPORTUNIES FOR SHOWERS/STORMS BUT TEMPS COULD BE A TOUCH
COOLER THAN ON FRI.
DETAILS:
WEDNESDAY THROUGH FRIDAY:
HIGH PRESSURE WHICH SETTLED OVER THE SOUTHERN WATERS WILL CONTINUE
TO SHIFT SOUTHWARD ON WED, WHICH WILL HERALD THE START OF A WARMING
TREND TO TEMPERATURES AND ALSO ALLOW FOR INCREASINGLY-RISING LEVELS
OF HUMIDITY. INCREASING HEAT AND HUMIDITY ARE EXPECTED BY THURS WITH
HEAT INDICES IN THE MID TO UPPER 90S; THE PEAK OF THE HEAT AND
HUMIDITY STILL LOOKS TO BE ON FRI, WITH THE POTENTIAL FOR DANGEROUS
HEAT INDICES AROUND 100-105 DEGREES OR PERHAPS GREATER, AS 850 MB
TEMPS RISE INTO THE LOW-20S C. SWLY FLOW LOOKS STRONG ENOUGH THROUGH
THIS PERIOD TO MITIGATE SEABREEZES, THUS VERY WARM TEMPS ARE
EXPECTED TO REACH INTO COASTAL AREAS. HEAT HEADLINES WILL PROBABLY
BE NEEDED AT SOME POINT FOR THE LATE-WEEK PERIOD; HEAT INDICES ARE
BORDERLINE THU BUT ARE MORE SOLID FOR FRI.
WED AND THURS LOOK TO FEATURE DRY WEATHER DESPITE BUILDING WARM
TEMPS AND RISING DEWPOINTS, WITH SUBSIDENCE AND LACK OF SUFFICIENT
FORCING MECHANISMS OFFSETTING A MODERATE DEGREE OF INSTABILITY. BY
FRIDAY, A WEAK COOL FRONT WILL BE WORKING ITS WAY SOUTHWARD, WHICH
WILL ALSO COINCIDE WITH THE PEAK OF THE HEAT AND HUMIDITY. WILL HAVE
TO SEE IF THIS FRONT LINES UP WITH PEAK HEATING TO FAVOR POTENTIAL
FOR STRONGER STORMS; CURRENTLY MACHINE-LEARNING SEVERE WEATHER PROGS
FROM COLORADO STATE SHOW LOW (5%) PROBS FOR SEVERE WEATHER FOR FRI.
THE WEEKEND:
THE COLD FRONT FROM FRIDAY THEN LOOKS TO STALL AND WEAKEN OVER OR
JUST SOUTH OF SOUTHERN NEW ENGLAND, IN A REGIME OF WEAK TROUGHING
PER ENSEMBLE MEANS. THIS IS A PATTERN WHICH WOULD KEEP OUR WEATHER
PATTERN UNSETTLED WITH PERIODS OF SHOWERS AND STORMS AROUND IN AND
NEAR THE REMNANT FRONTAL BOUNDARY, ALTHOUGH THE PLACEMENT OF IT WILL
BE KEY IN DETERMINING WHERE SHOWERS/STORMS WOULD BE MORE FAVORED.
FOR NOW KEPT POPS PRETTY GENERIC AT A 15-25% RANGE BUT THESE WILL
NEED TO BE BETTER REFINED AS WE MOVE THROUGH THE WORKWEEK.
IT IS POSSIBLE THAT HEAT AND HUMIDITY COULD LEAD TO ELEVATED HEAT
INDICES THIS WEEKEND, BUT LOCATION OF THE FRONT AND POTENTIAL FOR
CONSIDERABLE CLOUDINESS CASTS MORE UNCERTAINTY ON THOSE VALUES.
HIGHS IN THE MID TO UPPER 80S WITH HEAT INDICES IN THE LOWER TO MID
90S ARE CURRENTLY FORECAST, BUT THESE COULD NEED ADJUSTING EITHER UP
OR DOWN ONCE CONFIDENCE GROWS IN THE EXACT PLACEMENT OF THE
REMNANT FRONTAL BOUNDARY.
AVIATION /07Z 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 TUESDAY: HIGH CONFIDENCE.
VFR. NW WINDS PICK UP TO AROUND 10-15 KT, WITH GUSTS 20-25 KT
STARTING 13-15Z THRU SUNDOWN. WINDS THEN SLACKEN TO 5-10 KT
TONIGHT, HIGHER EASTERN TERMINALS.
TUESDAY: HIGH CONFIDENCE.
VFR CONTINUES WITH LIGHT NORTH WINDS; SEABREEZES ON BOTH COASTS
WHICH COULD DEVELOP ON THE EARLIER END OF SEABREEZE CLIMO, AROUND
14Z.
TUESDAY NIGHT: HIGH CONFIDENCE.
VFR, WITH LIGHT S WINDS. RADIATION FOG FOR SOUTHERN/SOUTHWEST
AIRPORTS IS POSSIBLE.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF
KBDL TERMINAL...HIGH CONFIDENCE IN TAF
OUTLOOK /WEDNESDAY THROUGH FRIDAY/...
WEDNESDAY THROUGH THURSDAY NIGHT: VFR. BREEZY.
FRIDAY: VFR. BREEZY. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH TUESDAY NIGHT: HIGH CONFIDENCE.
N/NW WINDS COULD GUST TO NEAR-SCA LEVELS (AROUND 20 KT) AROUND
EARLY TO MID MONDAY MORNING UNTIL MIDAFTERNOON, THOUGH I DIDN'T
THINK GUSTS OF 25+ KTS WOULD BE PERSISTENT ENOUGH FOR SCA
HEADLINES. NW WINDS THEN SUBSIDE TO LIGHT LEVELS TONIGHT, WHICH
REMAIN LIGHT NORTHERLY ON TUE (NEARSHORE SEABREEZES). WINDS THEN
BECOME S/SW AROUND 5-10 KT TUE NIGHT. SEAS MAINLY 3 FT OR LESS
THROUGH THE PERIOD, EXCEPT NEARING 4 FT EARLY THIS MORNING. NO
OBSTRUCTIONS TO VISIBILITY EXPECTED THRU TUE NIGHT.
OUTLOOK /WEDNESDAY THROUGH FRIDAY/...
WEDNESDAY THROUGH WEDNESDAY NIGHT: WINDS LESS THAN 25 KT.
THURSDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH LOCAL
GUSTS UP TO 30 KT. SEAS LOCALLY APPROACHING 5 FT.
THURSDAY NIGHT: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS
WITH AREAS OF GUSTS UP TO 30 KT. SEAS UP TO 5 FT.
FRIDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. SLIGHT CHANCE OF
RAIN SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...LOCONTO
NEAR TERM...LOCONTO
SHORT TERM...LOCONTO
LONG TERM...LOCONTO
AVIATION...LOCONTO
MARINE...LOCONTO
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