BOX issues Area Forecast Discussion (AFD) at Sep 9, 6:33 PM EDT271
FXUS61 KBOX 092233
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
633 PM EDT Tue Sep 9 2025
.SYNOPSIS...
Increasing cloudiness is expected tonight and overnight.
Overcast, cool and raw weather is expected Wednesday with
periods of rain showers, with conditions improving by Wednesday
evening. Otherwise, dry weather prevails for the rest of the
week and into the weekend as high pressure remains over New
England with seasonable temperatures.
&&
.NEAR TERM /THROUGH WEDNESDAY/...
Key Messages...
* Increasing cloudiness tonight and overnight. Scattered showers
over southeast New England, becoming more spotty/hit-or-miss
in the interior.
* Lows upper 40s to the mid/upper 50s, mildest over southeast
New England. Northeast breezes will make it feel cooler than
that.
Other than a few high clouds over the Cape and Islands, overall
a nice afternoon with temps in the upper 60s to lower to mid
70s, though it feels a little cooler owing to a northeast breeze
with gusts in the 20-25 mph range. This onshore breeze is due
to a tightening pressure gradient between high pressure
initially in place across much of New England and a broad low
pressure well to our south over the coastal Carolinas. While
this low pressure is expected to pass offshore of Southern New
England, we'll start to feel an increasing influence from it
starting tonight and into a good part of Wednesday.
So for tonight, we'll start off with mostly clear skies, however
increasing cloudiness is expected to expand north and west as
the night progresses. Low clouds/stratus expands north and west
soonest over the Cape and Islands and eventually into most of
Southern New England except into far northwest MA. Scattered
showers should primarily be focused over southeast New England
overnight and continuing into Wed morning; because these showers
will be moving northward into an increasingly dry airmass over
eastern MA and interior Southern New England, probably nothing
worse than an intermittent shower or drizzle at worst.
Lows in the mid/upper 40s to the middle 50s, though in the upper
50s/near 60 for the Cape and Islands. A northeast breeze
overnight will make it feel cooler than that though.
&&
.SHORT TERM /WEDNESDAY NIGHT/...
Key Messages...
* Cloudy, cool/raw with off and on periods of rain showers.
Highs in the 60s.
* Lingering showers over Cape Cod Wed night but drying out for
rest of Southern New England. Lows upper 40s to mid 50s.
Wednesday:
Wednesday is essentially a continuation of conditions that
likely will have taken place overnight, with overcast skies,
northeast breezes and periods of showers mainly over southeast
New England. This occurs as coastal low pressure makes its
closest pass to Southern New England, but passes east of
40N/70W.
The uncertainties in the forecast revolve around how long will
clouds/stratus start to scatter out and more specifically how it
affects high temps; and also on how much rain falls. Latest
guidance seems to hold onto cloud cover into much of the
afternoon, which could make for a cool, raw day with temps only
making into the 60s, and the hills in Worcester County could
even struggle to reach 60. Thus we undercut NBM high temps by
some 6-8 degrees. Regarding forecast QPF, leaned on the lighter
side closer to the global models with totals up to a quarter-
inch over southeast New England forecast; CAMs are quite a bit
wetter out over the Cape and Islands, in some solutions up to an
inch, but we view these are wet outliers in the absence of
convective enhancement.
Wednesday Night:
Steady improvement from west to east with clearing skies and
winds become light northerly. Could have some lingering showers
(ocean-enhanced?) out over the Cape and Islands before things
taper off by midnight. Will have to watch for possible fog
development, and this is particularly the case if daytime
temperatures remain cool/raw from slow-improving low clouds.
Lows upper 40s to the mid 50s.
&&
.LONG TERM /THURSDAY THROUGH TUESDAY/...
Key Points
* Dry and seasonable weather to end the week into the weekend
* Next best chance for rain appears Sunday
High pressure begins to drop down from the Hudson Bay in Canada,
helping push low clouds and drizzle out of the region. Temperatures
will rebound nicely with highs in the upper 70s to low 80s under
sunny skies. Cooler temperatures eventually arrive with the
Canadian high-pressure system building in, with temperatures on
Friday dropping to the low to mid-70s.
Forecast confidence breaks down heading into the weekend as weak
pieces of shortwave energy traverse the NW flow aloft. Mid-level
dry air appears more prevalent on Saturday, likely keeping things
dry outside of a spot shower or two. Sunday has a better chance for
rain as better mid-level moisture combined with a weak frontal
system moves through the region. High temperatures over the weekend
stay seasonable in the low to mid 70s. More dry air looks to work
in behind the frontal system for Monday, leading to drying
conditions and cooler temps in the upper 60s to low 70s.
&&
.AVIATION /00Z WEDNESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
00z TAF Update:
Tonight: High confidence in trends, but moderate on timing and
northwestward coverage of stratus.
VFR begins to gradually deteriorate through the night to BKN/OVC
MVFR stratus, soonest across the Cape and Islands (01-02z), and
between 04-08z for most other TAFs. Spotty rain showers or
drizzle overnight, with the best chance over southeast airports.
NE winds 5-10 kt, around 10-15 kt with gusts 25 kt Cape and
Islands.
Wednesday: Moderate confidence.
MVFR (MVFR/IFR Cape and Islands) to start with spotty rain
showers mainly south and east of the Mass Pike. Slow, gradual
improvement to SCT VFR through the aftn, but the exact timing is
uncertain. It will likely take longer for the Cape and Islands
to see improvement and they may remain sub-VFR all day. NE winds
around 5-10 kt interior / 10-15 kt with gusts to 25 kt Cape and
Islands, gradually becoming NNE/N through the afternoon.
Wednesday Night: High confidence.
Early MVFR-IFR for the Cape and Islands but should transition to
all VFR overnight. Patchy fog possible. Light north winds.
KBOS Terminal...Moderate confidence.
VFR turning MVFR overnight as stratus pushes north. Light
drizzle possible
KBDL Terminal...High confidence.
VFR with pockets of MVFR overnight with light drizzle possible.
Outlook /Thursday through Sunday/...
Thursday through Friday: VFR. Breezy.
Friday Night through Saturday: VFR.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
SCAs were extended into Wednesday evening to allow for winds
and seas to decrease. NE winds 10-15 kt with gusts 20-25 kt
tonight through Wed, with seas around 4-6 ft. Winds and seas
then begin to slowly decrease into Wednesday evening. Periods
of rain showers tonight and into Wednesday over the waters, but
then begins to taper off except over the eastern waters
Wednesday night.
Outlook /Thursday through Sunday/...
Thursday through Thursday Night: Winds less than 25 kt. Areas
of seas approaching 5 ft.
Friday: Winds less than 25 kt. Seas up to 5 ft.
Friday Night through Saturday: Winds less than 25 kt. Seas
locally approaching 5 ft.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT Thursday for ANZ254.
Small Craft Advisory until 6 AM EDT Thursday for ANZ255-256.
&&
$$
SYNOPSIS...Loconto/KP
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...KP
AVIATION...Loconto/KP
MARINE...Loconto/KP
Source:
BOX issues Area Forecast Discussion (AFD) at Sep 9, 6:33 PM EDT----------------
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