BOX issues Area Forecast Discussion (AFD) at Oct 21, 3:03 PM EDT078
FXUS61 KBOX 211903
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
303 PM EDT Tue Oct 21 2025
.SYNOPSIS...
Sunny skies and quiet weather continue this evening. A frontal
system will bring a period of showers late tonight into Wednesday
morning. We then enter into a cooler and unsettled weather pattern for late
in the workweek with partial cloudiness and cooler high
temperatures. Dry weather then continues into the weekend, but with
some potentially rather chilly nighttime lows.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Key Messages...
* Quick round of showers overnight into Wednesday morning.
* Dry and increasingly sunny through the afternoon.
Mid level ridging continues to provide a beautiful blue sky day this
afternoon and that will persist into the evening hours. The
exception is an area of high clouds over the Cape and islands thanks
to a weak ripple in the mid level flow. Around sunset we'll start to
see high clouds invading from the west, thickening and lowering with
time as they expand over southern New England tonight. This cloud
cover and eventual rainfall is associated with a mid level shortwave
and surface frontal system which moves through overnight and
Wednesday. The warm front lifts north overnight followed in quick
succession by a cold front on Wednesday. This is a progressive
system so the period of elevated PWATs (approaching 1") will be
brief, as will be the showers. However, given the dynamics in place
coincident with that moist column, isolated downpours are possible
before the showers exit east Wednesday morning (west) to early
afternoon (east). Rapid drying occurs behind the front leading to
clearing skies Wednesday afternoon. This also results in a cold
advection pattern which will lead to better mixing and wind gusts of
20 to 30 mph, especially over Cape Cod and the islands. Temperatures
will make it back up well into the 60s before cooler air fills in.
&&
.SHORT TERM /WEDNESDAY NIGHT/...
Key Messages...
* Quiet and dry.
A cool airmass remains overhead with a mid level trough digging in.
This means low temperatures about 10 degrees cooler than the night
previous, in the mid 30s to mid 40s for most.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Key Messages:
* Cooler and more unsettled for late in the week. Highs only in the
50s.
* High pressure brings dry weather this weekend but with some chilly
nighttime lows.
Details:
A deep upper trough at 500 mb and associated cooler lower-
tropopsheric airmass will be the primary driver of our weather
pattern late in the week into the early part of next week. This will
keep our weather cooler and somewhat unsettled too, with partial
cloudiness and spotty rain showers in western New England driven by
Great-Lakes-enhanced moisture. Highs in the mid 50s with lows in the
mid 40s. It's not until the weekend until high pressure returns with
sunny and dry weather. But the airmass remains cooler than normal,
so while we'll see more in the way of sunshine, high temps still
will range in the mid 50s, which are a few degrees cooler than
normal.
&&
.AVIATION /19Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
18z TAF Update...
This afternoon...High confidence.
VFR. SW wind gusts of 15-20 knots across the interior and 20-25
knots along the coast.
Tonight and Wednesday...High confidence in trends, but lower
confidence in timing.
VFR conditions continue this evening. Showers overspread the
interior between 03z and 09z...reaching the coastal plain
between 07 and 12Z. Brief downpours with a period of MVFR-IFR
conditions possible in any showers. The showers are progressive
with the bulk moving offshore by early Wed afternoon followed by
VFR conditions. SW winds may gust to 20+ knots at times and
near 25 knots along the south coast.
Wednesday night...High confidence.
VFR. SW winds 5-10 kts, gusting 15 to 20 kts at Cape and
islands terminals.
KBOS Terminal...High confidence in TAF.
KBDL Terminal...High confidence in TAF.
Outlook /Thursday through Sunday/...
Thursday: VFR. Breezy.
Thursday Night through Sunday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Tonight through Wednesday night...High confidence.
Persistent SW winds and long fetch will result in 3 to 6 foot seas
through Wednesday night...the highest of those seas will be
across the southern outer-waters. The winds will also gust from
the southwest at 20 to 25 knots at times with the strongest of
those across the southern waters. Therefore...small craft
headlines continue for our southern waters right through
Wednesday night and later shifts will likely need to extend
these headlines into Thursday.
Outlook /Thursday through Sunday/...
Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas. Slight chance of rain showers.
Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.
Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Friday Night through Saturday: Winds less than 25 kt.
Saturday Night through Sunday: Winds less than 25 kt. Slight
chance of rain showers.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 PM EDT this evening for ANZ231.
Small Craft Advisory until 8 AM EDT Thursday for ANZ232>235-
237-254>256.
&&
$$
SYNOPSIS...Loconto/BW
NEAR TERM...BW
SHORT TERM...BW
LONG TERM...Loconto
AVIATION...Loconto/BW
MARINE...Loconto/BW
Source:
BOX issues Area Forecast Discussion (AFD) at Oct 21, 3:03 PM EDT----------------
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