215
FXUS61 KBOX 131826
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
226 PM EDT Sun Sep 13 2026

.WHAT HAS CHANGED...
The heaviest rainfall has come to an end, with remaining showers
tapering off from west to east through early this evening.
Additional significant rainfall is not expected, though localized
nuisance flooding may linger given the 2 to 4 inches of rain that
fell across portions of Rhode Island and southeast Massachusetts
today. Lastly, Small Craft Advisories issued for most waters
starting Monday afternoon through Monday night for gusty winds.

&&

.KEY MESSAGES...

- Heaviest rainfall ending, drier overnight, though low clouds
  and areas of fog are possible. A stray early morning shower
  remains possible too.

- Dry and fall-like Monday into Tuesday, with a chilly start
  Tuesday morning.

- High pressure in control next week brings generally quiet
  weather. Brief bout of summer warmth and humidity expected
  Wed- Fri.

&&

.DISCUSSION...
KEY MESSAGE 1...Heaviest rainfall ending, drier overnight, though
low clouds and areas of fog are possible. A stray early morning
shower remains possible too.

The back edge of the heaviest rain is now working from west to east
across southern New England, with clouds thinning across eastern New
York and approaching western Massachusetts. Rainfall totals have
been impressive today, with many areas seeing 2 to 4 inches, mainly
across Rhode Island and southeast Massachusetts. The Flash Flood
Watch remains in effect through 6 PM. While the heaviest rain is
over, light to moderate showers linger and could still lead to
nuisance flooding. Expect these showers to continue for the next
couple of hours before wrapping up between 4 PM and 6 PM, though a
few may linger an additional hour or so across the outer Cape.

Drier conditions arrive overnight, though low clouds and areas of
fog may persist into early Monday morning. A final push of showers
is possible toward daybreak, though guidance has generally shown
this activity weakening as it approaches southern New England,
leaving just a spotty shower or two, mainly in the 4 AM to 8 AM time
frame. It is worth mentioning that some of the high-resolution
guidance indicates a bit of a resurgence in shower activity as it
approaches the coast, possibly picking up on some instability near
the shore. Nevertheless, this would not lead to impactful weather
and would be nothing like what we saw today.

KEY MESSAGE 2...Dry and fall-like Monday into Tuesday, with a chilly
start Tuesday morning.

Surface high pressure around 1020-1025 mb builds in from the Great
Lakes region on Monday, settles overhead Monday night, and remains
with us through Tuesday as a 1030 mb surface high. Little weather to
talk about during this time frame. While there is lingering moisture
early Monday morning, with some areas of fog, a much drier airmass
arrives by noon as PWATs fall below half an inch.

CAA during the day allows for a period of breezy northwest winds.
Forecast soundings through BUFKIT show a well-mixed boundary layer
upwards of 850 mb, which should allow most of the wind aloft to mix
to the surface. Winds aloft are 25 to 30 kt, resulting in surface
wind gusts of roughly 20 to 30 mph from the north-northwest. Highs
Monday afternoon are largely in the lower to middle 70s.

With high pressure overhead Monday night, winds decouple, allowing
for effective radiational cooling. Have opt`d to do a model blend to
show the coldest of the guidance. This would mean many of us wake up
Tuesday morning in the 40s; however, would not be shocked if towns
in far northwestern Franklin County dip to 38 to 40 degrees. That
being said, urban centers remain in the upper 40s to lower 50s.
Boston may retain enough heat due to the urban heat island effect to
maintain lows in the middle 50s. Lastly, there could be areas of
ground fog due to the abundant recent rainfall.

Heading into Tuesday, a crisp and dry day with dew points in the
50s, with some upper 40s possible in northern Massachusetts.
Meanwhile, 925 mb temperatures settle around +9C to +12C, which
would suggest high temperatures in the middle 60s to lower 70s. High
pressure slowly drifts east during the day, with winds shifting to a
north-northeasterly direction.

KEY MESSAGE 3...High pressure in control next week brings
generally quiet weather. Brief bout of summer warmth and
humidity expected Wed- Fri.

High pressure firmly in control by Tuesday will bring much drier
weather with it. Under dry NW flow dewpoints will be very comfortable
to start the week, in the 40s. This will be a comfortable taste of
Fall Tuesday when combined with high temperatures in the upper 60s
(coasts) to low 70s (inland). As the high shifts over the Atlantic
Wednesday flow turns southerly bringing the return of more summer-
like temperatures and dewpoints in the upper 70s and mid 60s
respectively. Still some uncertainty with regard to the forecast for
late week and next weekend. Zonal mid level flow continues with
potential for a low to cross somewhere in the vicinity of southern
New England; whether that stays to our north or goes overhead is
uncertain, but generally looking at a better shot of unsettled
weather late Thursday onward.

&&

.AVIATION /18Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18z TAF Update: Widespread rain ending from west to east this
afternoon.

Through 00z...Moderate confidence in trends and timing.

The heaviest rain is starting to exit from west to east across
southern New England, ending first west of the CT River Valley
around 19z, reaching the I-95 corridor around 21z, and moving east
of Cape Cod by 00z. While much of the night will be dry, a decaying
line of showers pushes through southern New England from 06z-10z.
Ceilings are generally LIFR to IFR, with some improvement overnight
to high-end IFR, if not MVFR. A drier airmass arrives predawn, which
will erode cloud cover and allow conditions to trend VFR between 10-
14z Monday.

Monday and Monday Night...High confidence.

VFR. NW to NNW winds 8 to 12 kt with gusts 20 to 25 kt. Winds ease
overnight, becoming light and variable under clear skies. Isolated
areas of ground fog are possible due to abundant recent rainfall.

Tuesday...High confidence.

VFR. Light N to NNE winds, becoming E/SE by the end of the day.

KBOS Terminal...Moderate confidence in TAF.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Tuesday through Friday/...

Tuesday: VFR. Breezy.

Tuesday Night through Wednesday Night: VFR.

Thursday: Mainly VFR, with local MVFR possible. Slight chance
SHRA.

Thursday Night: Mainly VFR, with local MVFR possible. Chance
SHRA.

Friday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Through Tuesday...High confidence.

Surface low pressure moves northeast from the southern coastal
waters Sunday afternoon, crossing into the Gulf of Maine overnight
before reaching Nova Scotia Monday morning. Meanwhile, high pressure
builds in from the Great Lakes region on Monday, resulting in a
tightening pressure gradient and gusty northerly winds Monday
afternoon through the overnight hours. There may be a brief period
of gusts around 25 kt, thus a marginal Small Craft Advisory has been
issued. Seas during this time are 2 to 3 ft across the nearshore
waters and 3 to 4 ft across the outer waters. However, the outermost
portions of the forecast zones may approach 5 ft.

Outlook /Tuesday through Friday/...

Tuesday: Winds less than 25 kt. Areas of seas approaching 5 ft.

Tuesday Night through Wednesday Night: Winds less than 25 kt.
Seas locally approaching 5 ft.

Thursday: Winds less than 25 kt.

Thursday Night: Winds less than 25 kt. Chance of rain showers.

Friday: Winds less than 25 kt. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch until 6 PM EDT this evening for CTZ004.
MA...Flood Watch until 6 PM EDT this evening for MAZ012-013-015>024.
RI...Flood Watch until 6 PM EDT this evening for RIZ001>008.
MARINE...Small Craft Advisory from 11 AM Monday to 2 AM EDT Tuesday for
     ANZ231>235-237-250-254>256.

&&

$$

DISCUSSION...BW/Dooley
AVIATION...BW/Dooley
MARINE...BW/Dooley