517
FXUS61 KBOX 181122
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
722 AM EDT FRI JUL 18 2025
SYNOPSIS
AN APPROACHING COLD FRONT MAY BRING A BRIEF SHOWER THROUGH THIS
EVENING. BEHIND THE FRONT, COOLER AND MUCH LESS HUMID AIR WILL
FOLLOW FRIDAY AND SATURDAY. ANOTHER COLD FRONT WILL LIKELY
BRING A ROUND OF SHOWERS AND THUNDERSTORMS TO THE REGION
SUNDAY. 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:
* MORE SEASONABLE AND MUCH LESS HUMID CONDITIONS TODAY
SURFACE COLD FRONT IS MOVING THROUGH SNE AT 06Z AND WILL BE OFFSHORE
BY DAYBREAK. A PERIOD OF GUSTY NW WINDS WILL FOLLOW THE FRONT
DURING THE MORNING BEFORE WINDS DIMINISH THIS AFTERNOON AS HIGH PRES
BUILDS IN FROM THE WEST. THE NW FLOW WILL USHER IN A MUCH DRIER
AIRMASS AS PWATS FALL TO 0.50 TO 0.75". SUBSIDENCE AND DRY AIR WILL
RESULT IN FULL SUNSHINE WITH A COOLER POST-FRONTAL AIRMASS AS 850 MB
TEMPS WILL BE AROUND 12-13C THIS AFTERNOON. EXPECT HIGHS 80-85 WITH
UPPER 70S HIGHER TERRAIN, AND WITH DECENT BL MIXING DEWPOINTS WILL
DROP INTO AND THROUGH THE 50S WITH SOME UPPER 40S DEWPOINTS ACROSS
INTERIOR NORTHERN MA SO MUCH MORE COMFORTABLE HUMIDITY LEVELS.
OVERALL, A FANTASTIC SUMMER AFTERNOON.
SHORT TERM /SATURDAY/
KEY MESSAGES:
* CLEAR AND COOL TONIGHT
* SUNNY AND WARM SAT WITH COMFORTABLE HUMIDITY LEVELS
HIGH PRES BUILDS OVER NEW ENG TONIGHT. CLEAR SKIES, LIGHT WINDS AND
A DRY AIRMASS WILL SET THE STAGE FOR GOOD RADIATIONAL COOLING WITH
LOWS DROPPING INTO THE 50S, EXCEPT 60-65 BOSTON METRO, NARRAGANSETT
BAY LOCATIONS AND OUTER CAPE.
ANOTHER BEAUTIFUL SUMMER DAY ON SATURDAY AS HIGH PRES REMAINS IN
CONTROL WITH SUNSHINE AND WARM TEMPS. FLOW BECOMES SOUTHERLY AS HIGH
MOVES OFFSHORE WHICH WILL BRING SLIGHTLY WARMER AIRMASS WITH 850 MB
TEMPS WARMING TO 15C. HIGHS WILL REACH LOW-MID 80S WITH STILL
COMFORTABLE HUMIDITY LEVELS FOR MUCH OF THE DAY. DEWPOINTS WILL BE
IN THE 50S, BUT CLIMB INTO THE 60S FROM SOUTH TO NORTH DURING THE
LATE AFTERNOON AND EVENING.
LONG TERM /SATURDAY NIGHT 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 /11Z FRIDAY THROUGH TUESDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
12Z TAF UPDATE: HIGH CONFIDENCE.
VFR THROUGH SAT. NW GUSTS 20-25 KT THROUGH THE MORNING,
DIMINISHING IN THE AFTERNOON WITH LOCAL SEA-BREEZES POSSIBLE
TOWARD EVENING. LIGHT TO CALM WIND TONIGHT THEN BECOMING SW
10-15 KT SAT.
KBOS TERMINAL...MODERATE TO HIGH CONFIDENCE IN TAF.
GUSTY NW WINDS THIS MORNING DIMINISHING IN THE AFTERNOON WHICH
MAY LEAD TO A SEA-BREEZE 20-22Z, THEN SHIFTING TO S AROUND 00Z.
CONFIDENCE IN SEA-BREEZE INCREASING.
KBDL TERMINAL...HIGH CONFIDENCE IN TAF.
OUTLOOK /SATURDAY NIGHT 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.
HIGH CONFIDENCE THROUGH SATURDAY.
SCAS IN EFFECT FOR OUTER WATERS UNTIL 18Z FOR COMBINATION OF WIND
AND SEAS. POST-FRONTAL NW GUSTS TO 25 KT THIS MORNING WILL DIMINISH
THIS AFTERNOON. LIGHT WINDS TONIGHT, THEN BECOMING SOUTHERLY 10-20
KT SAT AFTERNOON. MARGINAL SCA SEAS WILL SUBSIDE THIS AFTERNOON.
OUTLOOK /SATURDAY NIGHT 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...SMALL CRAFT ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR ANZ250-
251-254>256.
SYNOPSIS...KJC
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...KJC
AVIATION...KJC/HRENCECIN
MARINE...KJC
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