426
FXUS61 KBOX 171830
AFDBOX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE BOSTON/NORTON MA
230 PM EDT MON AUG 17 2026
WHAT HAS CHANGED
A RIP CURRENT STATEMENT HAS BEEN ISSUED FOR EAST-FACING BEACHES FROM
9 AM TO 8 PM TUESDAY.
KEY MESSAGES
- FAIR AND LESS HUMID TUESDAY WITH GRADUAL CLEARING. A HIGH RISK
OF RIP CURRENTS DEVELOPS ACROSS EAST-FACING BEACHES BY TUESDAY
AFTERNOON.
- NO WASHOUTS EXPECTED, THOUGH SEVERAL OPPORTUNITIES FOR
SHOWERS RETURN FROM MID TO LATE WEEK.
DISCUSSION
KEY MESSAGE 1...FAIR AND LESS HUMID TUESDAY WITH GRADUAL CLEARING. A
HIGH RISK OF RIP CURRENTS DEVELOPS ACROSS EAST-FACING BEACHES BY
TUESDAY AFTERNOON.
GRADUAL CLEARING DEVELOPS FROM W TO E TUESDAY AS LOW PRESSURE SLOWLY
PULLS AWAY FROM THE REGION. GUIDANCE SHOWS AREAS OF LOW CLOUDS AND
FOG LINGERING FOR MUCH OF THE DAY ACROSS COASTAL AREAS WITH THE HELP
OF CYCLONIC ONSHORE FLOW. THUS, EXPECTING HIGH TEMPERATURES TO STAY
IN THE LOWER TO MID 70S FOR COASTAL AREAS, AND PERHAPS EVEN THE
UPPER 60S FOR THE OUTER CAPE. IT WILL BE QUITE HUMID CLOSER TO THE
COAST WITH ONSHORE FLOW ADVECTING MOISTURE INLAND. ELSEWHERE, IT
WILL BE DRIER AS THE FLOW TURNS TO THE NW THROUGH THE DAY. FURTHER
INLAND, IT LOOKS TO BE A WARMER AND DRIER DAY WITH HIGHS IN THE LOW
TO MID 80S. HEAT INDEX VALUES CLIMB INTO THE UPPER 80S TO NEAR 90
FOR A TIME TUESDAY AFTERNOON. FOR THOSE HEADING TO THE BEACH TUESDAY
AFTERNOON, A RIP CURRENT STATEMENT IS IN EFFECT FOR EAST-FACING
BEACHES TUESDAY. THOSE HEADING TO THE BEACH SHOULD REMAIN AWARE OF
LOCAL CONDITIONS AND CHECK WITH LIFEGUARDS OR BEACH STAFF REGARDING
RIP CURRENT RISKS AT THEIR SPECIFIC LOCATION.
KEY MESSAGE 2...NO WASHOUTS EXPECTED, THOUGH SEVERAL OPPORTUNITIES FOR SHOWERS
RETURN FROM MID TO LATE WEEK.
GENERALLY ZONAL FLOW ALOFT PREVAILS WEDNESDAY
WHILE AN UPPER LEVEL LOW TRACKS WELL NORTH ACROSS THE HUDSON
BAY. CONDITIONS ARE LIKELY TO STAY DRY DURING THE DAY WITH
TEMPERATURES IN THE LOW TO MID 80S. A WEAK PIECE OF SHORTWAVE
ENERGY SHIFTS IN FROM THE WEST LATER WEDNESDAY. WHILE THE BETTER
FORCING REMAINS FURTHER NORTH AND WEST, THERE IS A LOW
PROBABILITY FOR AN ISOLATED SHOWER IN WESTERN MA WEDNESDAY
NIGHT.
ANOTHER SHORTWAVE IN THE FLOW MOVES THROUGH THURSDAY ACCOMPANIED BY
BETTER ASCENT AND PLUME OF ABOVE NORMAL MOISTURE TO SUPPORT SHOWERS.
THERE IS STILL SOME UNCERTAINTY ACROSS GUIDANCE WITH THE TRACK OF
THE WAVE. THE ECMWF (ENS AND DETERMINISTIC) LEANS TOWARD A MORE
SOUTHERN TRACK WITH THE HIGHER ENSEMBLE PROBABILITIES (60-80%) FOR
ANY RAIN ACCUMULATION EXTENDING ACROSS THE SOUTH COAST TO SOUTHEAST
MA, AND CAPE/ISLANDS. THE GEFS/GFS HAS SHOWN A WIDER FOOTPRINT OF
SHOWERS WITH SIMILAR PROBABILITIES ACROSS ALL OF SOUTHERN NEW
ENGLAND. ANY AMOUNTS ARE LIKELY TO RANGE FROM A TRACE TO A FEW
TENTHS OF AN INCH.
WE'LL BE IN A POST-FRONTAL AIRMASS FRIDAY RESULTING IN SLIGHTLY
COOLER TEMPERATURES IN THE MID 70S TO LOW 80S AND A DOWNTICK IN
HUMIDITY. THE EASTERN COASTAL AREAS WILL LIKELY END UP ON THE COOLER
END OF THAT TEMPERATURE RANGE GIVEN THE EASTERLY ONSHORE FLOW. HIGH
PRESSURE BUILDS IN FROM THE WEST BRINGING DRY CONDITIONS TO MOST OF
THE REGION. HOWEVER, THERE ARE INDICATIONS ACROSS MODEL GUIDANCE OF
A BOUNDARY STALLING OFF THE EAST COAST WITH A SERIES OF EMBEDDED
SHORTWAVES RIDING THAT BOUNDARY FRIDAY THROUGH THE WEEKEND. THIS MAY
BRING PERIODIC CHANCES FOR SHOWERS, PERHAPS SOME THUNDERSTORMS IF
THE WAVES ALIGN WITH DIURNAL HEATING. THE HIGHER RISK FOR
SHOWERS WILL THE FOR SOUTH COAST EXTENDING TO CAPE COD/ISLANDS.
AVIATION /18Z MONDAY THROUGH SATURDAY/
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THIS AFTERNOON INTO TONIGHT...MODERATE CONFIDENCE IN TRENDS,
LOWER CONFIDENCE IN TIMING.
POCKETS OF IFR DEVELOPING AS WINDS SHIFT TO THE SE AND E, MAINLY
ACROSS COASTAL TERMINALS. POTENTIAL FOR LIFR FOR THE CAPE AND
ISLANDS OVERNIGHT. LIGHT NORTHERLY WINDS, BECOMING CALM ACROSS
THE INTERIOR.
TUESDAY...MODERATE CONFIDENCE.
MVFR TO IFR CONDITIONS TO START, WITH IMPROVEMENT TO VFR FROM WEST
TO EAST BETWEEN 15Z AND 20Z. EASTERN TERMINALS, INCLUDING CAPE COD,
MAY EXPERIENCE A LATER IMPROVEMENT TO VFR, POSSIBLY NOT UNTIL 22Z TO
00Z. LIGHT NORTHWEST WINDS ACROSS THE INTERIOR, WITH NORTH TO NORTH-
NORTHEAST WINDS ACROSS EASTERN MASSACHUSETTS AT LESS THAN 10 KT.
KBOS TERMINAL...MODERATE CONFIDENCE.
MVFR UNTIL 21Z, THEN IFR WITH SE WINDS SHIFTING TO THE E AFTER
00Z. IFR CONDITIONS CONTINUE OVERNIGHT WITH WINDS SHIFTING TO
THE NE AND EVENTUALLY N AFTER 12Z.
KBDL TERMINAL...MODERATE CONFIDENCE.
MVFR CONDITIONS THROUGH THE OVERNIGHT. LOW CHANCE FOR FG AT THE
TERMINAL. LIGHT AND VARIABLE WINDS.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY THROUGH WEDNESDAY NIGHT: VFR.
THURSDAY THROUGH FRIDAY: VFR. CHANCE SHRA.
FRIDAY NIGHT: VFR. SLIGHT CHANCE SHRA.
SATURDAY: VFR. CHANCE SHRA.
MARINE
FORECASTER CONFIDENCE LEVELS...
LOW - LESS THAN 30 PERCENT.
MODERATE - 30 TO 60 PERCENT.
HIGH - GREATER THAN 60 PERCENT.
THROUGH TUESDAY NIGHT...MODERATE CONFIDENCE.
SCA CONDITIONS SUBSIDE TUESDAY AS LOW PRESSURE SHIFTS FARTHER
EAST. SEAS SUBSIDE TO 2 TO 4 FT, WITH LIGHT NORTHERLY TO NORTH-
NORTHWEST WINDS GENERALLY LESS THAN 15 KT. HIGH RISK OF RIP
CURRENTS FOR EAST-FACING BEACHES ACROSS E MASSACHUSETTS AS WELL
AS THE CAPE AND NANTUCKET.
OUTLOOK /WEDNESDAY THROUGH SATURDAY/...
WEDNESDAY THROUGH WEDNESDAY NIGHT: WINDS LESS THAN 25 KT.
THURSDAY: WINDS LESS THAN 25 KT. SLIGHT CHANCE OF RAIN SHOWERS.
THURSDAY NIGHT: WINDS LESS THAN 25 KT. CHANCE OF RAIN SHOWERS,
SLIGHT CHANCE OF THUNDERSTORMS.
FRIDAY THROUGH SATURDAY: WINDS LESS THAN 25 KT. CHANCE OF RAIN
SHOWERS.
BOX WATCHES/WARNINGS/ADVISORIES
CT...NONE.
MA...HIGH RISK FOR RIP CURRENTS FROM TUESDAY MORNING THROUGH TUESDAY
EVENING FOR MAZ007-015-016-019-022-024.
HIGH RISK FOR RIP CURRENTS UNTIL 8 PM EDT THIS EVENING FOR MAZ023-
024.
RI...HIGH RISK FOR RIP CURRENTS UNTIL 8 PM EDT THIS EVENING FOR
RIZ006>008.
MARINE...SMALL CRAFT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR
ANZ232>235-237.
SMALL CRAFT ADVISORY UNTIL 2 AM EDT TUESDAY FOR ANZ254>256.
DISCUSSION...MENSCH/FT
AVIATION...FT/RM
MARINE...FT
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