495
FXUS61 KBOX 311801
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
201 PM EDT Mon Aug 31 2026

.WHAT HAS CHANGED...
No significant changes.

&&

.KEY MESSAGES...

- A cool and wet start to meteorological fall. Some rain could
  be heavy, leading to poor drainage flooding.

- Unsettled weather late Wed into Thursday, with several rounds
  of showers and thunderstorms. Low confidence on exact timing.

- Improving weather Friday and into the holiday weekend. Other
  than a spot diurnal shower each day, dry weather prevails with
  a mix of clouds and sun. Cooler than normal with highs in the
  70s and lows in the 50s, along with onshore breezes.

&&

.DISCUSSION...
KEY MESSAGE 1...A cool and wet start to meteorological fall. Some
rain could be heavy, leading to poor drainage flooding.

The backdoor cold front that pushed southwest of New England this
morning starts to shift back to the northeast today, with increasing
cloud cover this afternoon. As advertised the past several days,
there are multiple rounds of beneficial rainfall this week, with the
first round coming late tonight through Tuesday. With the frontal
boundary shifting northeast, PWATs increase to between 1.8-2.0
inches, interacting with a weak wave of low pressure riding along
the boundary.

Timing-wise, rain aims to arrive around midnight west of the CT
River Valley and around the time of the Tuesday morning commute for
the I-95 corridor. Looking at BUFKIT, do see warm rain processes
with the warm cloud layer around 10k feet. Locally heavy downpours,
especially during the daytime Tuesday, are possible, which may lead
to localized street and poor drainage flooding. This coincides with
the Day 1-2 ERO Marginal Risk (level 1 out of 4) for excessive
rainfall.

Do think there will be a thin axis of heaviest rainfall across the
southwest section of our CWA. Rainfall amounts are in the
neighborhood of half an inch to an inch, with lesser amounts east of
I-95, where totals are in the range of a quarter to half an inch.
Since these are showers versus stratiform rain, there could be areas
of higher and lower amounts within a relatively short distance.
However, a subtle shift northeast could put some of the heaviest
rainfall across parts of central Massachusetts and eastern
Connecticut. Additionally, there`s a lower chance for thunder,
mainly Tuesday afternoon, with a few hundred J/kg of CAPE across
mainly western Massachusetts and Connecticut, although it`s not a
significant risk.

Rain tapers off late Tuesday, with drier conditions overspreading
the region Tuesday night into early Thursday morning. Given the
clouds, expect a much cooler start to Tuesday, with highs mainly in
the upper 60s to lower 70s. A true nod to the first day of
meteorological fall.


KEY MESSAGE 2...Unsettled weather late Wed into Thursday, with
several rounds of showers and thunderstorms. Low confidence on exact
timing.

1025 mb high pressure over the Maritimes should provide dry weather
much of Wed, especially across eastern MA, while a frontal boundary
lurks to the west and southwest of SNE. This front will eventually
move northeast as a warm front later Wed and especially Wed night,
resulting in an increased risk for showers and thunderstorms across
SNE late Wed/Wed night. Cooler temps Wed, with 1025 Maritime high
and ESE onshore flow, limiting max temps in the upper 60s and lower
70s.

Trailing/secondary short wave and associated cold front impact the
region around Thu. Potential for thunderstorms to become strong to
severe during this time, as warm sector airmass overspreads SNE.
However, better instability/higher theta-e airmass appears to remain
southwest of SNE. Thus, potential for severe weather and flash
flooding here looks limited at this time range. Heat and humidity
return Thu with warm sector airmass, highs in the lower 80s and dew
pts in the upper 60s and lower 70s.


KEY MESSAGE 3...Improving weather Friday and into the holiday
weekend. Other than a spot diurnal shower each day, dry weather
prevails with a mix of clouds and sun. Cooler than normal with highs
in the 70s and lows in the 50s, along with onshore breezes.

Definitely a sign of fall approaching, with robust northern stream
Friday yielding a baroclinic 998 mb maritime low late Fri/Sat. This
will yield a cool, brisk NE flow into the SNE over the weekend.
Highs likely remaining in the 70s and overnight lows in the 50s. It
will feel even cooler over southeast MA, including Cape Cod and the
Islands, with northeast winds 15-25 mph. Cool cyclonic flow aloft
will yield diurnal clouds each day and possibly a spot shower.
Otherwise, dry weather prevails. Possibly warmer and less wind for
Memorial Day Monday, as high amplitude trough moves offshore and
1025 mb high settles over SNE.

&&

.AVIATION /18Z MONDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

18Z TAF Update:

Through 00Z...High confidence.

VFR and dry. However, mid-level clouds are increasing from west to
east a slow-moving front lifts east-northeast. Coastal sea breezes
continue today at around 10 kt, while inland winds remain southerly
at less than 6 kt.

Tonight...High confidence in trends, moderate confidence in timing.

Ceilings lower to low-end MVFR, if not IFR, as SHRA arrives from
west to east between 06Z and 12Z. Conditions eventually deteriorate
to LIFR across interior terminals by 08-10Z, with visibilities
lowering to 2-5 SM. There is a low chance of lightning, with the
greatest probability across western terminals in southern New
England, particularly KBDL. Winds shift from south to southeast
overnight, remaining light across interior southern New England and
increasing to 8-10 kt at coastal terminals.

Tuesday...Moderate confidence.

Pockets of LIFR to start; otherwise, a mixture of IFR and MVFR
ceilings persists, with periodic showers and isolated TSRA possible.
East-southeast winds of 10-15 kt are expected at coastal terminals
and 6-10 kt at interior terminals.

Tuesday Night...Moderate confidence.

MVFR ceilings generally prevail along and east of I-95, while areas
farther inland remain IFR to LIFR. Onshore easterly winds and
chances for SHRA continue.

KBOS Terminal...High confidence in trends, moderate confidence in timing.

KBDL Terminal...High confidence in trends, moderate confidence in timing.

Outlook /Tuesday Night through Saturday/...

Wednesday: Mainly VFR, with local IFR possible. Chance SHRA,
slight chance TSRA.

Wednesday Night: MVFR/IFR conditions possible. SHRA, chance
TSRA.

Thursday: Mainly VFR, with local IFR possible. Chance SHRA,
chance TSRA.

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

Friday: VFR. Slight chance SHRA.

Friday Night through Saturday: VFR. Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Tuesday Night...High confidence.

High pressure situated over the Gulf of Maine shifts northeast
toward the Canadian Maritimes tonight as a semi-stationary front
lifts northeast. A series of low pressure systems will ride along
this boundary, beginning tonight and bringing unsettled weather.
Rain develops late tonight into Tuesday, potentially leading to poor
visibility. Southerly winds overnight become east-southeast Tuesday
and easterly Tuesday night, with speeds of 10 to 15 kt and gusts
around 20 kt. Seas remain below 2 ft tonight, then slowly build to 2
to 3 ft Tuesday and possibly 3 to 5 ft by late Tuesday night or
early Wednesday morning. Building seas may warrant a Small Craft
Advisory for the outer waters, but no headlines have been issued at
this time.

Outlook /Tuesday Night through Saturday/...

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Rain showers likely, chance of thunderstorms.

Thursday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, chance of thunderstorms.

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

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.

Friday Night: Winds less than 25 kt.

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...Dooley/Nocera
AVIATION...Dooley/Nocera
MARINE...Dooley/Nocera