224
FXUS61 KBOX 190651
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
251 AM EDT SAT JUL 19 2025
SYNOPSIS
DRY AND PLEASANT WEATHER WITH COMFORTABLE HUMIDITY LEVELS CONTINUES
TODAY. ANOTHER COLD FRONT MAY BRING SCATTERED SHOWERS AND A FEW
THUNDERSTORMS WITH HEAVY RAINFALL LATE TONIGHT AND SUNDAY MORNING,
WITH PERHAPS ANOTHER ROUND OF SCATTERED STRONG TO SEVERE STORMS
SOMETIME SUNDAY AFTERNOON INTO SUNDAY EVENING. MUCH LESS HUMID ALONG
WITH COOLER THAN NORMAL TEMPERATURES AND DRY WEATHER FOR EARLY NEXT
WEEK. WARMING TREND THEN BEGINS AROUND THE MIDDLE OF NEXT WEEK, WITH
HEAT AND HUMIDITY RETURNING FOR THURSDAY AND ESPECIALLY FRIDAY.
NEAR TERM /UNTIL 6 PM THIS EVENING/
KEY MESSAGES:
* MOSTLY SUNNY AND WARM TODAY WITH COMFORTABLE HUMIDITY
HIGH PRES REMAINS IN CONTROL TODAY WITH SUNSHINE AND WARM TEMPS.
SUNSHINE IN THE MORNING WILL MIX WITH HIGH CLOUDS AND SOME
DEVELOPING STRATO-CU IN THE AFTERNOON, BUT OVERALL MOSTLY SUNNY
SKIES WILL PREVAIL. THE HIGH SHIFTS TO THE EAST THIS AFTERNOON
ALLOWING SOUTHERLY FLOW TO DEVELOP WITH WARMING LOW LEVEL TEMPS.
HIGHS WILL BE IN THE LOW-MID 80S WITH SOME UPPER 80S IN THE CT
VALLEY AND PORTIONS OF NE MA. HOWEVER, DEVELOPING SEA-BREEZES WILL
KEEP THE IMMEDIATE COAST A FEW DEGREES COOLER. HUMIDITY LEVELS WILL
BE MANAGEABLE FOR MOST OF THE DAY WITH DEWPOINTS IN THE 50S, BUT
PWATS ARE INCREASING AND DEWPOINTS WILL RISE INTO THE 60S TOWARD
EVENING.
SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/
KEY MESSAGES:
* INCREASING HUMIDITY TONIGHT WITH A FEW SHOWERS AND T-STORMS
POSSIBLE LATE TONIGHT INTO SUN MORNING. LOCALLY HEAVY RAINFALL
POSSIBLE
* A SECOND ROUND OF SCATTERED STRONG TO SEVERE T-STORMS POSSIBLE
LATE SUN AFTERNOON AND EVENING
DRY WEATHER WILL LAST THROUGH THIS EVENING, THEN FORCING FOR ASCENT
WILL BEGIN TO INCREASE OVERNIGHT AHEAD OF AN APPROACHING MID LEVEL
SHORTWAVE. IN ADDITION, INSTABILITY AND MOISTURE WILL BE INCREASING
AHEAD OF AN APPROACHING WARM FRONT AS HIGHER THETA-E AIR PLUME MOVES
INTO SNE ALONG WITH HIGHER PWATS. EXPECT A FEW SHOWERS AND T-STORMS
TO DEVELOP LATE TONIGHT INTO SUN MORNING AS THE SHORTWAVE MOVES
THROUGH, WITH BEST CHANCE ACROSS CT, RI AND SE MA IN VICINITY OF THE
APPROACHING WARM FRONT. PWATS INCREASE TO 1.5 TO 2 INCHES SO THERE
IS A RISK OF HEAVY RAINFALL AND HREF IS INDICATING LOW PROBS OF 3+
INCHES OF RAIN IN 3 HOURS FOCUSED ON THE SOUTH COAST WHICH WOULD
BRING A LOCALIZED FLASH FLOOD THREAT SUN MORNING IF THIS
MATERIALIZES. HOWEVER, FORECAST CONFIDENCE IN HEAVY RAIN IS LOW AS
HEAVY RAIN THREAT IS MUTED ON GLOBAL GUIDANCE, AND THERE IS
UNCERTAINTY WITH LOCATION OF MAIN CONVECTION WHICH COULD END UP TO
THE SOUTH. IT WILL BE A MILD NIGHT WITH INCREASING HUMIDITY AS
DEWPOINTS APPROACH 70 BY SUN MORNING.
THE SHORTWAVE MOVES TO THE EAST BY LATE MORNING WITH SUBSIDENCE
BRINGING A PERIOD OF DRY CONDITIONS. THEN A COLD FRONT WILL BE
DROPPING SOUTH FROM NORTHERN NEW ENG WITH LATEST GUIDANCE PUSHING
THE FRONT THROUGH SNE FROM NW TO SE DURING THE AFTERNOON AND
EVENING. WARM AND HUMID AIRMASS WILL CONTRIBUTE TO MODERATE
INSTABILITY DEVELOPING IN THE AFTERNOON WITH A SECOND ROUND OF
SCATTERED SHOWERS AND T-STORMS POSSIBLE, WITH A RISK OF SEVERE
WEATHER. COVERAGE OF STORMS WILL DEPEND ON EXTENT OF ANY CLEARING
BEHIND MORNING SHORTWAVE WHICH ADDS AN ELEMENT OF UNCERTAINTY WITH
HOW QUICKLY THE ENVIRONMENT WILL RECOVER AND EXTENT OF SUBSEQUENT
CONVECTION ALONG THE COLD FRONT. MODERATELY SHEARED ENVIRONMENT
DEVELOPS AHEAD OF A MID LEVEL TROUGH WITH 30-40 KT 0-6KM SHEAR AND
FORECAST CAPES ARE 1000-2000 J/KG. ASSUMING WE GET ENOUGH AFTERNOON
SUNSHINE THIS ENVIRONMENT WILL BE SUPPORTIVE OF SCATTERED STRONG TO
SEVERE T-STORMS. THE MAIN LIMITING FACTOR IS POOR MID LEVEL LAPSE
RATES BUT THIS MAY BE OVERCOME BY FAVORABLE INSTABILITY/SHEAR
PARAMETERS AND FAVORABLE TIMING OF COLD FRONT PASSAGE WITH DECENT
FORCING FOR ASCENT WHICH IS REFLECTED BY INCREASING UPDRAFT HELICITY
SWATHS FROM HREF. MOST OF THE CAMS ALSO SHOWING A FAIRLY ACTIVE
CONVECTIVE ENVIRONMENT ALONG THE COLD FRONT AND MACHINE LEARNING
PROBS HAVE INCREASED SEVERE WEATHER THREAT FOR SUNDAY, WITH DAMAGING
WIND THE PRIMARY THREAT. SPC HAS UPGRADED SNE TO A SLIGHT RISK.
LOCALLY HEAVY RAINFALL WILL BE A SECONDARY THREAT GIVEN HIGH PWAT
AIRMASS. EXPECTED TIMING OF STORMS WILL BE 2-8 PM AND WHILE THE BEST
CHANCE WILL BE IN THE INTERIOR, STORMS COULD MAKE IT TO THE SOUTH
COAST LATE SUN OR SUN EVENING GIVEN FAVORABLE SHEAR.
IT WILL BE A VERY WARM AND HUMID DAY WITH HIGHS MID-UPPER 80S AND
DEWPOINTS INTO THE LOWER 70S. HEAT INDICES ARE EXPECTED TO REACH 90-
95 IN THE CT VALLEY AND PORTIONS OF RI AND EASTERN MA.
LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/
KEY MESSAGES:
* COOLER WITH LOW HUMIDITY AND BELOW NORMAL TEMPS MON AND TUE
* WARMING TREND MID TO LATE NEXT WEEK, WITH HEAT AND HUMIDITY
RETURNING THU AND ESPECIALLY FRI. CHANCES FOR SHOWERS/STORMS
INCREASE FRI.
SCATTERED SHOWERS AND STORMS WILL MOVE OFF THE COAST SUN EVENING AS
FRONT MOVES OFFSHORE, FOLLOWED BY A PERIOD OF GUSTY NW WINDS INTO
EARLY MON. DECENT SURGE OF COOLER AIR MOVES IN EARLY NEXT WEEK IN
POST-FRONTAL AIRMASS AS 850 MB TEMPS BOTTOM OUT AROUND 6-8C TUE
MORNING. BELOW NORMAL TEMPS EXPECTED MON AND TUE WITH LOW HUMIDITY.
HIGHS GENERALLY 75-80 WITH TUE LIKELY THE COOLER DAY AFTER A COOL
NIGHT MON NIGHT. WINDS EXPECTED TO DIMINISH MON AFTERNOON WITH LIGHT
WINDS TUE.
UPPER TROUGH LIFTS OUT AFTER TUE WITH RISING HEIGHTS AS SUBTROPICAL
RIDGE BUILDS OVER THE MIDWEST AND OHIO VALLEY WITH SNE ON THE NE
PERIPHERY OF THE RIDGE. WARMING TREND BEGINS WED AND IT APPEARS
INCREASING HEAT AND HUMIDITY RETURN THU AND ESPECIALLY FRI WHEN 850
MB TEMPS MAY APPROACH +20C. GEFS AND EPS SHOWING MODERATE TO HIGH
PROBS OF 90+ BY FRI WITH POTENTIAL FOR HEAT ADVISORY CRITERIA BEING
MET. BEST CHANCE FOR DIURNAL SHOWERS AND T-STORMS WILL BE FRI AS AS
MORE ACTIVE NORTHERN STREAM DESCENDS SOUTHWARD INTO NEW ENG, BUT
TIMING AND AMPLITUDE OF SHORTWAVE ENERGY IS UNCERTAIN AT THIS TIME
RANGE.
AVIATION /07Z SATURDAY THROUGH WEDNESDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
06Z TAF UPDATE:
TODAY...HIGH CONFIDENCE.
VFR. SSW WINDS AROUND 10 KNOTS EXCEPT FOR LOCALIZED SEA BREEZES
DEVELOPING ALONG PORTIONS OF THE IMMEDIATE COAST.
TONIGHT AND SUNDAY...MODERATE CONFIDENCE.
VFR, THEN AREAS OF MVFR CIGS DEVELOPING AFTER 06Z WITH A FEW
SHOWERS OR T-STORMS POSSIBLE POSSIBLE LATE TONIGHT INTO SUN
MORNING, ESPECIALLY SOUTH OF THE MA PIKE. LOW RISK FOR IFR.
IMPROVEMENT TO VFR SUN AFTERNOON, BUT A SECOND ROUND OF
SCATTERED STRONG T-STORMS POSSIBLE AFTER 18Z, ESPECIALLY
INTERIOR. ANY STORMS MAY BE ACCOMPANIED BY STRONG WIND GUSTS,
HEAVY DOWNPOURS AND BRIEF IFR.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF. SEA-BREEZE LIKELY
DEVELOPING BY 14Z BUT WINDS VEERING TO S TOWARD 21Z.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT THROUGH MONDAY: VFR. BREEZY.
MONDAY NIGHT THROUGH TUESDAY NIGHT: VFR.
WEDNESDAY: VFR. BREEZY.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH SUNDAY...HIGH CONFIDENCE.
SOUTHERLY WINDS MAINLY BELOW SCA THRESHOLDS THROUGH SUN, ALTHOUGH A
BRIEF PERIOD OF 20-25 KT GUSTS POSSIBLE OVER NE MA WATERS TONIGHT.
CONFIDENCE NOT HIGH ENOUGH FOR SCA AT THIS TIME. WILL HAVE TO WATCH
FOR SCATTERED T-STORMS OVER SOUTH COASTAL WATERS LATE TONIGHT AND SUN
MORNING.
OUTLOOK /SUNDAY NIGHT THROUGH WEDNESDAY/...
SUNDAY NIGHT: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN
SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
MONDAY THROUGH WEDNESDAY: WINDS LESS THAN 25 KT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...KJC
AVIATION...KJC
MARINE...KJC
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