691
FXUS61 KBOX 181807
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
207 PM EDT FRI JUL 18 2025
SYNOPSIS
DRY AND PLEASANT WEATHER WITH COMFORTABLE HUMIDITY LEVELS CONTINUES
TONIGHT INTO SATURDAY. ANOTHER COLD FRONT MAY BRING SCATTERED
SHOWERS AND A FEW THUNDERSTORMS TO THE REGION TOWARD DAYBREAK SUNDAY
WITH PERHAPS ANOTHER ROUND SOMETIME LATE SUNDAY INTO SUNDAY EVENING.
HIGH PRESSURE WILL BRING COOLER AND LESS HUMID WEATHER MONDAY AND
TUESDAY WITH BELOW NORMAL TEMPERATURES, THEN MUCH WARMER CONDITIONS
RETURN BY NEXT THURSDAY WITH A CHANCE OF SHOWERS AND
THUNDERSTORMS.
NEAR TERM /THROUGH TONIGHT/
KEY MESSAGES...
* MOSTLY CLEAR & COOL TONIGHT WITH LOWS MAINLY IN THE 50S
DETAILS...
A RIDGE OF HIGH PRESSURE BUILDS OVER THE REGION TONIGHT. THIS WILL
ALLOW FOR MAINLY CLEAR SKIES...LIGHT/CALM WINDS AND A GOOD NIGHT OF
RADIATIONAL COOLING GIVEN THE DRY AIRMASS IN PLACE FOR JULY
STANDARDS. LOW TEMPS WILL BOTTOM OUT MAINLY IN THE 50S WITH PERHAPS
EVEN SOME UPPER 40S IN THE NORMALLY COOLEST OUTLYING LOCATIONS OF
WESTERN MA. MEANWHILE...THE URBAN HEAT ISLANDS OF BOSTON/PROVIDENCE
ONLY BOTTOM OUT IN THE LOWER TO MIDDLE 60S.
SHORT TERM /SATURDAY THROUGH SATURDAY NIGHT/
KEY MESSAGES...
* MOSTLY SUNNY SAT...HIGHS MAINLY IN THE MIDDLE TO UPPER 80S
* MILDER SAT NIGHT WITH LOWS IN THE UPPER 60S TO THE LOWER 70S ALONG
WITH SCATTERED SHOWERS & A FEW T-STORMS POSSIBLE AFTER MIDNIGHT
DETAILS...
SATURDAY...
HIGH PRESSURE SLIDES EAST OF THE REGION ON SAT. THIS WILL ALLOW A
WARMER AIRMASS TO BEGIN TO OVERSPREAD THE REGION...BUT WITH
COMFORTABLE HUMIDITY LEVELS. HIGH TEMPS SHOULD REACH MAINLY IN THE
MIDDLE TO UPPER 80S WITH A FEW SPOTS IN THE LOWER CT RIVER VALLEY
PERHAPS FLIRTING WITH 90. IT WILL BE A FEW DEGREES COOLER ALONG
PORTIONS OF THE IMMEDIATE EASTERN MA COAST WITH SEA BREEZES.
SATURDAY NIGHT...
DRY WEATHER SHOULD PREVAIL SAT EVENING...BUT CLOUDS WILL BE ON THE
INCREASE AHEAD OF AN APPROACHING SHORTWAVE AND ASSOCIATED MID-LEVEL
WARM FRONT. THERE IS A PRETTY GOOD ELEVATED INSTABILITY BURST AHEAD
OF THIS WARM FRONT AS SHOWALTER INDICES QUICKLY DROP FROM OVER 10
TO BELOW ZERO OVERNIGHT. THEREFORE...EXPECT SCATTERED SHOWERS AND A
FEW THUNDERSTORMS TO BE POSSIBLE AFTER MIDNIGHT AND ESPECIALLY
TOWARD DAYBREAK SUNDAY. THERE ALSO MIGHT BE POCKETS OF HEAVY
RAINFALL AS PWATS CLIMB INTO THE 1.50 TO 2 INCHES. LOW TEMPS WILL BE
MUCH MILDER THAN TONIGHT...ONLY BOTTOMING OUT IN THE UPPER 60S TO
THE LOWER 70S.
LONG TERM /SUNDAY THROUGH THURSDAY/
KEY MESSAGES:
* ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS LATE SAT NIGHT-SUN
* DRY AND COOLER MON-TUE
* WARMING TREND WED-THU WITH VERY WARM AND HUMID CONDITIONS
RETURNING BY THU
NEXT MID LEVEL TROUGH AND COLD FRONT APPROACHES ON SUNDAY. SOME
SHOWERS ARE POSSIBLE LATER SAT NIGHT, BUT MAIN CONCERN IS FOR
POTENTIAL FOR T-STORMS ON SUNDAY. INCREASING MOISTURE AND
INSTABILITY AHEAD OF THE FRONT WITH HEIGHT FALLS WILL RESULT IN A
RISK FOR SCATTERED SHOWERS AND T-STORMS. 0-6KM SHEAR 30-40 KT SO
THERE WILL BE A SEVERE WX RISK AND CSU MACHINE LEARNING PROBS
SHOWING A LOW RISK FOR SEVERE WX WITH WIND THE PRIMARY THREAT.
HOWEVER, MID LEVEL LAPSE RATES ARE MEAGER WHICH IS A LIMITING
FACTOR. PWATS NEARING 2 INCHES SUNDAY SO LOCALLY HEAVY RAINFALL ALSO
A RISK. MUCH MORE HUMID SUNDAY AS 70+ DEWPOINTS RETURN, WITH HIGHS
INTO THE MID 80S.
THE FRONT REACHES THE COAST SUN EVENING THEN MOVES OFFSHORE
FOLLOWED BY MUCH COOLER AND DRIER AIRMASS MON INTO TUE WITH 850
MB TEMPS BOTTOMING OUT AROUND 5C 12Z TUE. THIS IS PRETTY
ANOMALOUS FOR MID- LATE JULY. EXPECT BELOW NORMAL TEMPS MON-TUE,
THEN A WARMING TREND FOLLOWS WED INTO THU AS THE HIGH MOVES
OFFSHORE WITH QUICK RECOVERY IN 850 MB TEMPS WHICH ARE BACK TO
17-18C ON THU. HIGHS SHOULD BE BACK WELL INTO THE 80S ON THU AND
POSSIBLY 90 AS GEFS SHOWING LOW- MOD PROBS OF 90+. INSTABILITY
INCREASES ON THU WITH DECENT MID LEVEL LAPSE RATES FORECASTED SO
THERE WILL BE CHANCE FOR SHOWERS AND T- STORMS BUT THIS WILL
DEPEND ON TIMING OF UPSTREAM SHORTWAVE ENERGY.
AVIATION /18Z FRIDAY THROUGH TUESDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
18Z TAF UPDATE...
THIS AFTERNOON INTO TONIGHT...HIGH CONFIDENCE.
VFR. NNW WINDS QUICKLY BECOMING LIGHT/CALM THIS EVENING. ANY
LOCALIZED SEA BREEZES ALONG THE IMMEDIATE COAST THAT DEVELOP WILL
COME TO AN END BY 01Z/02Z.
SATURDAY...HIGH CONFIDENCE.
VFR. SSW WINDS AROUND 10 KNOTS EXCEPT FOR LOCALIZED SEA BREEZES
DEVELOPING ALONG PORTIONS OF THE IMMEDIATE COAST.
SATURDAY NIGHT...MODERATE CONFIDENCE.
VFR DURING THE EVENING...BUT SOME MVFR CIGS MAY DEVELOP ACROSS PARTS
OF THE REGION AFTER MIDNIGHT. IN ADDITION...THE RISK FOR SCATTERED
SHOWERS AND A FEW T-STORMS WILL INCREASE AFTER MIDNIGHT AND
ESPECIALLY BY DAYBREAK. SSW WINDS 5-10 KNOTS.
KBOS TERMINAL...HIGH CONFIDENCE IN TAF.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /SUNDAY THROUGH TUESDAY/...
SATURDAY NIGHT: VFR. BREEZY. CHANCE SHRA.
SUNDAY: MAINLY VFR, WITH LOCAL MVFR POSSIBLE. BREEZY. CHANCE
SHRA, CHANCE TSRA.
SUNDAY NIGHT THROUGH TUESDAY: VFR.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MEDIUM - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
TONIGHT THROUGH SATURDAY NIGHT...HIGH CONFIDENCE.
HIGH PRESSURE MOVES OFF THE WATERS TONIGHT AND THEN PUSHES EAST OF
THE WATERS SAT AS A WARM FRONT APPROACHES BY SAT NIGHT. WINDS WILL
BE LIGHT TONIGHT INTO SAT MORNING...WITH SUSTAINED SPEEDS GENERALLY
UNDER 15 KNOTS. S WINDS MAY GUST TO 20+ KNOTS AND PERHAPS BRIEFLY UP
TO 25 KNOTS SAT NIGHT ACROSS OUR NORTHERN OUTER-WATERS. LATER SHIFTS
MAY NEED TO CONSIDER A MARGINAL SMALL CRAFT ADVISORY FOR THE
NORTHERN OUTER-WATERS...BUT OTHER THAN THAT NOT EXPECTING ANY MARINE
HEADLINES OVER THIS TIME PERIOD.
OUTLOOK /SUNDAY THROUGH TUESDAY/...
SATURDAY NIGHT: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING
5 FT. CHANCE OF RAIN SHOWERS.
SUNDAY: WINDS LESS THAN 25 KT. SEAS LOCALLY APPROACHING 5 FT.
CHANCE OF RAIN SHOWERS, SLIGHT CHANCE OF THUNDERSTORMS.
SUNDAY NIGHT THROUGH TUESDAY: WINDS LESS THAN 25 KT.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...NONE.
RI...NONE.
MARINE...NONE.
SYNOPSIS...FRANK/KJC
NEAR TERM...FRANK
SHORT TERM...FRANK
LONG TERM...KJC
AVIATION...FRANK/KJC
MARINE...FRANK/KJC
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