BOX issues Area Forecast Discussion (AFD) at Sep 22, 4:01 PM EDT372
FXUS61 KBOX 222001
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
401 PM EDT Tue Sep 22 2026
.WHAT HAS CHANGED...
No changes to current weather headlines. Confidence in an
impactful coastal storm for Friday into this weekend is
increasing.
&&
.KEY MESSAGES...
- Dry, cool, and breezy conditions continue through Thursday.
- Monitoring the potential for a strong coastal low to arrive
late week, bringing chances for strong winds, rainfall, and
coastal flood/erosion concerns through the weekend.
&&
.DISCUSSION...
KEY MESSAGE 1...Dry, cool, and breezy conditions continue
through Thursday.
Not anticipating much change to the forecast through Thursday.
A sprawling high pressure to our north will maintain cooler
conditions with gusty east to northeast winds. There should be a
brief period this evening where gusts subside before another
surge of colder air starts the gustiness again. The strongest
gusts should be from late morning into the afternoon Wednesday.
Slightly less breezy conditions for Thursday.
Across the southern coastal waters, Gale Warnings remain in
effect for Wednesday and Thursday.
KEY MESSAGE 2...Monitoring the potential for a strong coastal
low to arrive late week, bringing chances for strong winds,
rainfall, and coastal flood/erosion concerns through the
weekend.
While there is still a large amount of uncertainty in the
guidance, the overarching trend is indicating the low slowly
meanders north and retrograding west into the waters south of
Block Island and Nantucket; however, how close the low tracks to
the southern coast is still a large question. It is important
to note that the exact track and strength of the low will
strongly influence the timing and magnitude of gusts, QPF, and
how far inland the rain extends. The latest ECMWF is indicating
the low passes closer to Long Island whereas the latest GFS is
showing the low passing closer to the outer Cape and Nantucket.
Depending on the track the low takes, the onset of the strongest
winds could be as early as Friday evening or as late as
Saturday afternoon. Regardless, confidence is slowly increasing
in at least Gale Force winds (34kts/40mph), with the possibility
of Storm Force winds (48kts/55mph) Friday night/Saturday,
across the southern waters leading to an upgrade of the Gale
Watch to a Gale Warning for the southern and southeastern
waters.
This prolonged period of gusty northeasterly winds will build
rough seas and raise the threat for coastal flooding and
erosion, especially for east facing beaches and harbors. Latest
coastal flooding guidance from the Stevens Institute shows
greatest risk for at least minor coastal flooding for Nantucket
Harbor around the high tidal cycles Friday, Friday night, and
Saturday. The coastal flooding risk is slowly increasing for
Boston Harbor as well, although to a slightly lesser extent
compared to Nantucket.
&&
.AVIATION /20Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through 00Z...High confidence.
VFR for most. Local MVFR cloud bases between 020-025 possible
towards southeast MA, and perhaps across some of the higher
terrain of central and western MA. Gusty E to NE winds diminish
with sunset. MVFR cloud bases should also dissipate.
Tonight...High confidence.
Mainly VFR. NE winds of 5 to 15 kt tonight with 20-25 kt gusts
at times across the southeast New England coast and 25-30 kt for
Nantucket.
Wednesday and Wednesday Night...High confidence.
Mainly VFR. NE winds of 10 to 20 kt with gusts of 20 to 30 kt,
strongest towards the southeast New England coast. Gusts near
35 kt for Nantucket.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Thursday through Sunday/...
Thursday: VFR. Windy with gusts up to 35 kt.
Thursday Night: VFR. Strong winds with local gusts up to 40 kt.
Friday: VFR. Strong winds with gusts up to 45 kt. Chance SHRA.
Friday Night: VFR. Strong winds with gusts up to 40 kt. Chance
SHRA.
Saturday: VFR. Strong winds with gusts up to 40 kt. Chance
SHRA, slight chance TSRA.
Saturday Night: Mainly VFR, with local MVFR possible. Strong
winds with local gusts up to 40 kt. Chance SHRA, slight chance
TSRA.
Sunday: Mainly VFR, with areas MVFR possible. Windy with gusts
up to 35 kt. Chance SHRA, slight chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
Through Wednesday Night...High Confidence.
NE winds 15-20 kt with gusts up to 25 kt at times will
continue, as strong 1030+ mb high pressure over southeast
Ontario moves eastward into Quebec. This northeast fetch will
yield rough seas on the ocean waters. Dry weather and good
visibility prevail. Potential for gale force gusts appear to
hold off until Wed and beyond. Seas increase to 6-13 ft outside
the bays, harbors and sounds by Wednesday evening and night.
Outlook /Thursday through Sunday/...
Thursday: Strong winds with gusts up to 45 kt. Rough seas up to
16 ft.
Thursday Night: Moderate risk for gale force winds with local
gusts up to 45 kt. Rough seas up to 17 ft. Chance of rain
showers.
Friday: gale force winds with gusts up to 45 kt. Rough seas up
to 20 ft. Chance of rain showers.
Friday Night: gale force winds with gusts up to 45 kt. Rough
seas up to 22 ft. Chance of rain showers, slight chance of
thunderstorms.
Saturday: gale force winds with gusts up to 45 kt. Rough seas
up to 21 ft. Rain showers likely, chance of thunderstorms.
Saturday Night: Strong winds with local gusts up to 45 kt.
Rough seas up to 19 ft. Rain showers likely, slight chance of
thunderstorms.
Sunday: Strong winds with gusts up to 35 kt. Rough seas up to
16 ft. Rain showers likely, slight chance of thunderstorms.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ007-
015-016-019>024.
RI...High Risk for Rip Currents until 8 PM EDT this evening for RIZ002-
004>008.
MARINE...Small Craft Advisory until 8 PM EDT Thursday for ANZ230-250-
251.
Gale Warning from 8 PM Wednesday to 8 PM EDT Thursday for
ANZ231-254.
Gale Warning from 5 AM Wednesday to 8 PM EDT Thursday for
ANZ232>235-237-281.
Small Craft Advisory from 5 AM Wednesday to 8 PM EDT Thursday
for ANZ236.
Gale Warning from 2 AM Wednesday to 8 PM EDT Thursday for
ANZ255-256-282-283.
&&
$$
DISCUSSION...Belk/McMinn
AVIATION...Belk/McMinn
MARINE...Belk/McMinn
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 22, 4:01 PM EDT----------------
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