115
FXUS61 KBOX 221721
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
121 PM EDT TUE JUL 22 2025
SYNOPSIS
ONE LAST COOLER DAY TODAY BEFORE THE UPWARD TREND FOR
TEMPERATURES AND HUMIDITY STARTS MIDWEEK EXTENDING INTO FRIDAY.
DANGEROUS HEAT IS POSSIBLE FOR FRIDAY AS HIGHS APPROACH THE
UPPER 90S AND HUMIDITY WILL BRING HEAT INDICES INTO THE LOWER
100S. HEAT AND HUMIDITY CONTINUE THROUGH THE WEEKEND, BUT AT A
LESSER DEGREE FOLLOWING A COLD FRONT FRIDAY. THE CHANCE FOR
SHOWERS AND STORMS RETURNS FRIDAY THROUGH THE WEEKEND.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGE:
* ANOTHER RELATIVELY COOLER DAY WITH TEMPERATURES IN THE 70S TO
AROUND 80.
DETAILS...
HIGH PRESSURE CONTINUES OVER THE REGION TODAY WITH THE HIGH PRESSURE
CENTER POSITIONED OVER QUEBEC. THE WEAK PRESSURE GRADIENT UNDER THE
HIGH WILL PROMOTE LIGHT N/NW WINDS WITH LOCALIZED SEA BREEZES ALONG
THE IMMEDIATE COASTLINE. 850MB TEMPERATURES HOVER AROUND 8-10C,
SIMILAR TO MONDAY, IF NOT SLIGHTLY COOLER. THIS WILL BRING ANOTHER
DAY OF RELATIVELY COOLER TEMPERATURES WITH HIGHS IN THE UPPER 70S TO
LOW 80S FOR THE INTERIOR. SEA BREEZES WILL KEEP IT A BIT COOLER FOR
THE IMMEDIATE COAST IN THE MID TO UPPER 70S. MAINLY SUNNY DAY
OVERALL WITH SOME SCATTERED DIURNAL CLOUDS DEVELOPING TOWARD THE
AFTERNOON.
SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/
KEY MESSAGES:
* WARMING TREND IN TEMPERATURES STARTS, DAYTIME HIGHS CLOSER TO
NORMAL.
DETAILS...
TONIGHT:
MINIMAL CLOUD COVER WILL RESULT IN ANOTHER COOLER NIGHT WITH THE
HELP OF RADIATIONAL COOLING. ALTHOUGH NOT AS COOL AS MONDAY NIGHT,
TEMPERATURES SHOULD DROP INTO THE UPPER 50S-LOW 60S CLOSER TO THE
COAST AND MID-UPPER 50S FOR THE INTERIOR.
WEDNESDAY:
AN UPPER LEVEL RIDGE SHIFTS FURTHER EAST OVER SOUTHERN NEW ENGLAND
ON WEDNESDAY WITH THE SURFACE PRESSURE CENTER SETTLED OFFSHORE. THIS
WILL MARK THE START OF AN UPWARD TREND IN TEMPERATURES AND HUMIDITY.
ALTHOUGH POSSIBLE BY THE END OF THE WEEK (SEE LONG TERM DISCUSSION),
IMPACTFUL HEAT ISN'T EXPECTED WEDNESDAY. 850MB TEMPERATURES WARM A
FEW DEGREES FROM TUESDAY BRINGING HIGHS BACK AROUND NORMAL FOR THIS
TIME OF YEAR IN THE UPPER 70S-LOW 80S FOR THE SOUTH COAST AND
CAPE/ISLANDS AND LOW-MID 80S FOR THE REMAINING AREAS. ALTHOUGH
HUMIDITY IS EXPECTED TO SLOWLY RISE, THE AIRMASS IS STILL DRY
OVERALL KEEPING IT DRY. SW WINDS AT 5-15 MPH.
LONG TERM /THURSDAY THROUGH TUESDAY/
KEY MESSAGES:
* WARMING TREND CONTINUES THURSDAY INTO FRIDAY ALONG WITH
INCREASING HUMIDITY.
* ELEVATED HEAT INDICES THURSDAY, POSSIBLY REACHING DANGEROUS LEVELS
BY FRIDAY. HEAT HEADLINES POSSIBLE.
* DRY THURSDAY BEFORE FRONT ARRIVES FRIDAY, BRINGING A CHANCE
FOR SHOWERS AND STORMS THAT MAY EXTEND INTO THE WEEKEND.
HOWEVER, UNCERTAINTY REMAINS.
DETAILS...
THE MAIN AXIS OF A 500MB RIDGE CONTINUES TO SHIFT ACROSS SOUTHERN
NEW ENGLAND THURSDAY, SHIFTING SOUTH AND EAST BY FRIDAY. THERE IS A
STRONG SIGNAL DISPLAYED BY ENSEMBLE GUIDANCE FOR ANOMALOUSLY
WARM TEMPERATURES WITH 850MB TEMPS 2-3 STANDARD DEVIATIONS
ABOVE NORMAL AS TEMPS PEAK AROUND 20C FRIDAY. 925MB
TEMPERATURES RANGE 24-28C AMONG MOST MODEL GUIDANCE, POTENTIALLY
AS HIGH AS 30C BASED ON SOME DETERMINISTIC SOLUTIONS FRIDAY.
SOUTHERLY FLOW WILL HELP ADVECT IN HIGHER AMOUNTS OF MOISTURE
INCREASING HUMIDITY. SO MORE HOT AND HUMID WEATHER INCOMING FOR
THURSDAY AND FRIDAY, POTENTIALLY AT DANGEROUS LEVELS.
HIGH TEMPERATURES THURSDAY WILL LIKELY RANGE IN THE UPPER 80S TO LOW
90S IN MOST PLACES. BREEZY SW FLOW SHOULD SHUT DOWN SEA BREEZES
ALONG THE WATERS OF THE NORTH AND SOUTH SHORES, AND BOSTON ON
THURSDAY KEEPING TEMPERATURES SIMILAR TO THE INTERIOR AREAS. THE
CAPE/ISLANDS AND SOUTH COAST SHOULD BE SLIGHTLY COOLER GIVEN THE
ONSHORE FLOW WITH HIGHS IN THE LOW TO MID 80S. WITH THE HUMIDITY
FACTORED IN, HEAT INDICES RISE INTO THE LOW TO MID 90S ON THURSDAY.
ENSEMBLES ARE IN AGREEMENT WITH THE HEAT PEAKING FRIDAY, ALIGNING
WITH THE WARMEST TEMPERATURES ALOFT POSITIONING OVER THE REGION.
MODEL SOUNDINGS SHOW SUFFICIENT MIXING BY THE AFTERNOON SUPPORTING A
HOT AND BREEZY DAY. THIS WILL BOOST HIGHS SEVERAL DEGREES FROM
THURSDAY WITH HIGHS IN THE LOW TO MID 90S AND HEAT INDICES IN THE
UPPER 90S TO LOW 100S. IT IS BECOMING MORE LIKELY THAT WE WILL NEED
HEAT HEADLINES, ESPECIALLY FOR FRIDAY. THE PRESENCE OF DEEPER
MOISTURE AND AN APPROACHING SHORTWAVE/COLD FRONT WILL INCREASE
CHANCES FOR SHOWERS AND THUNDERSTORMS FRIDAY. DETAILS STILL NEED TO
BE IRONED OUT, ESPECIALLY WITH THE TIMING OF THE FRONT AS THAT WILL
IMPACT THE CHANCES FOR SEVERE (PEAK HEATING/INSTABILITY LINING UP
WITH BEST FORCING). WITH GUIDANCE SHOWING AS LEAST MARGINAL
INSTABILITY ABOUT, WE'LL HAVE TO KEEP AN EYE ON THIS FOR SEVERE
POTENTIAL. CSU ML GUIDANCE HAS NUDGED THE REGION TO A 15-30%
PROBABILITY FOR SEVERE WEATHER ON FRIDAY, AND NSSL ML PROBS HAVE
SIMILAR PROBABILITIES FOR FRIDAY.
ENSEMBLE GUIDANCE INDICATES A TREND TOWARD A MORE UNSETTLED PATTERN
FOR THE WEEKEND WITH ZONAL FLOW ALOFT AND THE PASSAGE OF A WEAK
DISTURBANCE OR TWO. TEMPERATURES WILL BE COOLER THAN THEY WERE LATE
WEEK, BUT IT STAYS ON THE HUMID SIDE. CHANCES FOR SHOWERS AND
STORMS, ESPECIALLY FAVORED ALONG ANY RESIDUAL BOUNDARIES AROUND.
AVIATION /17Z TUESDAY THROUGH SATURDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
18Z TAF UPDATE:
TUESDAY...HIGH CONFIDENCE.
VFR. LIGHT N WINDS 5-10 KTS, EXCEPT SE ALONG THE COASTS UNDER
SEABREEZES. SEA BREEZES KICK OUT BETWEEN 03-05Z WITH WINDS
TURNING BACK S.
TUESDAY NIGHT: MODERATE CONFIDENCE.
VFR CONDITIONS. LIGHT S/SSW WINDS. POTENTIAL FOR AREAS OF
RADIATION FG/BR FOR BDL/BAF AND SE MA. LOWER CONFIDENCE ON THE
COVERAGE/EXTENT OF IT.
WEDNESDAY: HIGH CONFIDENCE.
VFR. SW/SSW WINDS 6-12 KTS.
WEDNESDAY NIGHT: HIGH CONFIDENCE.
VFR. SW WINDS 6-12 KTS BECOMING GUSTIER TOWARDS DAYBREAK.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY: VFR. BREEZY.
THURSDAY NIGHT: MAINLY VFR, WITH LOCAL IFR POSSIBLE. BREEZY.
FRIDAY: VFR. BREEZY. SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA.
FRIDAY NIGHT: MAINLY VFR, WITH AREAS IFR POSSIBLE. BREEZY.
SLIGHT CHANCE SHRA, SLIGHT CHANCE TSRA, PATCHY BR.
SATURDAY: MAINLY VFR, WITH LOCAL IFR POSSIBLE. SLIGHT CHANCE
SHRA, SLIGHT CHANCE TSRA.
SATURDAY NIGHT: MAINLY VFR, WITH AREAS IFR POSSIBLE. CHANCE
SHRA, SLIGHT CHANCE TSRA, PATCHY BR.
SUNDAY: CHANCE SHRA, SLIGHT CHANCE TSRA, PATCHY BR.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH WEDNESDAY NIGHT: HIGH CONFIDENCE.
S/SE WINDS TUESDAY AT 6-12 KTS. SEAS LESS THAN 3 FT. BREEZY
S/SSW WINDS ON WEDNESDAY AT 10-15 KTS. SEAS LESS THAN 3 FT.
WINDS BECOME GUSTIER NEAR 25 KTS AND SEAS BEGIN TO BUILD TO 3-4
FT ALONG THE FAR NORTHERN WATERS WEDNESDAY NIGHT. SCA MAY BE
NEEDED.
OUTLOOK /THURSDAY THROUGH SUNDAY/...
THURSDAY: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS UP
TO 30 KT.
THURSDAY NIGHT: LOW RISK FOR SMALL CRAFT ADVISORY WINDS WITH
GUSTS UP TO 30 KT. SEAS LOCALLY APPROACHING 5 FT. PATCHY FOG.
AREAS OF VISIBILITY 1 TO 3 NM.
FRIDAY: MODERATE RISK FOR SMALL CRAFT ADVISORY WINDS WITH GUSTS
UP TO 25 KT. AREAS OF SEAS APPROACHING 5 FT. PATCHY FOG.
VISIBILITY 1 TO 3 NM.
FRIDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. SLIGHT CHANCE OF RAIN SHOWERS, SLIGHT CHANCE OF
THUNDERSTORMS, PATCHY FOG. VISIBILITY 1 TO 3 NM.
SATURDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS,
PATCHY FOG. VISIBILITY 1 TO 3 NM.
SATURDAY NIGHT THROUGH SUNDAY: WINDS LESS THAN 25 KT. CHANCE OF
RAIN SHOWERS, PATCHY FOG. VISIBILITY 1 TO 3 NM.
BOX WATCHES/WARNINGS/ADVISORIES
CT...HEAT ADVISORY FROM 11 AM THURSDAY TO 8 PM EDT FRIDAY FOR
CTZ002>004.
MA...HEAT ADVISORY FROM 11 AM THURSDAY TO 8 PM EDT FRIDAY FOR
MAZ003>007-010>019-026.
RI...HEAT ADVISORY FROM 11 AM THURSDAY TO 8 PM EDT FRIDAY FOR
RIZ001>004.
MARINE...NONE.
SYNOPSIS...HRENCECIN/MCMINN
NEAR TERM...MCMINN
SHORT TERM...MCMINN
LONG TERM...HRENCECIN
AVIATION...MCMINN
MARINE...MCMINN
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