Severe Thunderstorm Warning 68, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
234 PM EDT Sat Sep 6 2025

.SYNOPSIS...
Strong to severe thunderstorms move through interior Southern
New England through late this afternoon, with weakening
thunderstorms into eastern Massachusetts and Rhode Island early
this evening. Thunderstorms taper to a period of steady light
rain overnight. Cloudy and rainy conditions along with cooler
temperatures are expected for Sunday. Otherwise...much of the
work week looks dry and very pleasant outside the risk for a few
brief showers around mid- week.

&&

.NEAR TERM /THROUGH TONIGHT/...
235 PM Update:

Key Messages:

* Severe thunderstorms expected into western and central MA and
  northern CT through 6 PM. Damaging straight line winds,
  frequent lightning, heavy rain are the main threats, but a
  tornado or two may occur.

* Weakening storms into eastern MA and RI between approx 6-10
 PM; more limited/isolated severe weather potential exists for
  these storms.

* Overcast with periods of rain showers for the overnight.

Severe Thunderstorm Watch 607 is in effect until 8 PM this
evening for all of northern CT, western to central to
eastern/northern MA (including Boston), and Providence County in
Rhode Island.

Active afternoon is beginning to get underway, as regional
radar is showing a line of strong thunderstorms which primarily
trail from the Berkshires to central NJ, moving towards the
northeast around 40 mph. Some of these storms have already
become severe and a couple in the lower Hudson Valley are
showing signs of rotation.

A relatively uncommon combination of wind shear (both low-
level and through a deep depth) and a moderate degree of
instability (e.g. about 1500 J/kg of CAPE) is present across
much of interior Southern New England, including northern CT and
western/central MA. The ongoing storms will be moving into this
environment between now and 6 PM, and be capable of strong to
damaging straight line winds, frequent lightning, and heavy
downpours. However rather strong low-level rotation (0-1 km
shear of 20-25 kt) will favor a risk for a tornado or two, from
cells ahead of the main line of storms and within the line of
storms itself. Instances of severe weather appear greatest for
northern CT and western and central MA in this timeframe.

Further eastward, into much of eastern MA and northern RI, with
weakening instability, we expect a general downtrend in storm
intensity as the storms move into these areas after 6 PM.
However we can't rule out isolated instances of severe weather
into eastern MA and northern RI. Low level wind shear isn't
quite as pronounced as in interior Southern New England, so the
severe weather threats shift to more of a straight line wind
damage type. Even still, severe weather may prove short-lived
for these areas given the timing, as approaching sundown and
southerly flow off the water leads to a less-unstable setting.

The cold front itself becomes increasingly slow/stalled out
somewhere near or in vicinity of the I-95 corridor. Mainly a
period of steady rain is expected for the evening and overnight,
with a few in-cloud flashes/rumbles of thunder possible; but by
then, the severe weather potential will have ended. Overcast and
cooler temps for the overnight to early Sunday morning period,
with lows in the mid to upper 50s.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Key Messages:

* Rain showers linger into Sunday morning, especially across eastern
  MA.

* Cooler temps arrive to start off the week.

Sunday and Sunday Night...

Rain showers continue into Sunday morning, with pockets of
moderately heavy rainfall at times, as an anafrontal wave lingers
over southern New England. At this time, expecting heaviest rain
across and southeast of I-95. Rain should move out to sea by late
afternoon or early evening, but the interior should start drying out
late morning or early afternoon. Given the lingering cloud cover and
rain, expecting afternoon high temps to remain in the mid to upper
60 and struggle to reach 70 (with the exception of the outer Cape
and Islands... in the low 70s).

&&

.LONG TERM /MONDAY THROUGH FRIDAY/...
Key Messages:

* Mainly dry and pleasant for much of next week with cool night and
  mild days

* Offshore low may graze coast midweek, bringing chance for a few
  showers Wednesday

Once the rain and storms from the weekend clears with the exit of a
cold front, high pressure builds in over the region once more. 925
mb temperatures generally sit around or just below 10C for the
mornings, then getting to around 15C for daytime temperatures. Highs
through much of the week will likely be mostly in the 70s with some
areas in the upper 60s. A brief warmup over the region is possible
heading into Thursday as 925 mb temps get close to 20C and ensemble
probs for surface temperatures greater than 75 around 50% or higher;
the GEFS has probabilities over Boston, SE MA, and the river valleys
around 20% for temperatures at or above 80F. This warmth will be
short-lived though as another cold front pushes its way through the
region, ushering cooler temperatures in for Friday. Ensembles
indicate that some below normal temperatures may settle into the
region for the end of the week in its wake with highs in the 60s for
most (lower 70s for the CT River Valley).

Much of this period looks quiet aside from a low passing offshore
midweek. This may bring a chance for some showers into eastern MA,
RI, and the Cape and Islands Wednesday through Thursday night.

&&

.AVIATION /19Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

18z TAF Update:

Today...Moderate confidence.

Line of strong to severe TSRA moving through western and central
MA and CT between 19-23z. Frequent lightning, heavy rain
reducing visby, and damaging winds are the main threats from
severe thunderstorms. Weakening storms moving into the BED-BOS-
PVD corridor between 22-01z. For the Cape and Islands, mainly
VFR. SW winds 10-15 kt with gusts 25 kt outside of storms.

Tonight...Moderate confidence.

For TAFs east of I-95, TS thru about 02z, then mainly as SHRA
overnight. Areas northwest are low-end VFR through 06z/08z,
then lower to MVFR with pockets of IFR. SSW wind shifts to N
behind the cold front, but the Cape and Islands maintains a SSW
flow overnight.

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

MVFR to IFR in stratus and periods of SHRA through the morning
hours. Rain begins to taper off with cigs/visbys improving to
VFR into the afternoon. NW to NE winds 5-10 kt.

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

VFR into this afternoon with SW winds gusting between 25 and 30
knots. Possible -SHRA and -TSRA activity after 22z as a line of
storms moves from west to east but they will be weakening on
approach. Front becomes hung up overnight into Sunday morning with
lingering showers and MVFR ceilings.

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

VFR until 18z/19z, after a line of strong to severe thunderstorms
will likely approach from the west. Front becomes hung up overnight
into Sunday morning with lingering showers and MVFR ceilings.

Outlook /Monday through Wednesday/...

Sunday Night through Monday Night: VFR.

Tuesday: VFR. Breezy.

Tuesday Night through Wednesday: Breezy. Slight chance SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

* A Small Craft Advisory: In effect through 8 PM for all waters.

Through Sunday Night...High Confidence.

SW winds 25-30 kt through this afternoon/early tonight, with
seas around 3-5 ft. Weakening thunderstorms moving over the
southern and eastern nearshore waters, though a couple may
produce strong winds and frequent lightning. SMWs may be needed.

Otherwise, winds become NW/N tonight at sub-SCA levels, which
continues into Sunday. Seas 2-4 feet, while seas remain
elevated for the southern waters 3-5 feet.

Outlook /Monday through Wednesday/...

Sunday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.

Monday through Monday Night: Winds less than 25 kt.

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

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers.

Wednesday: Low risk for Small Craft Advisory winds with gusts
up to 25 kt. Seas up to 5 ft. 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
     ANZ230>237-250-251-254>256.

&&

SYNOPSIS...Loconto/McMinn
NEAR TERM...Loconto
SHORT TERM...McMinn
LONG TERM...Hrencecin
AVIATION...Loconto/Hrencecin
MARINE...Loconto/Hrencecin

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
343 PM EDT Sat Sep 6 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0250 PM     Tstm Wnd Dmg     1 SSE Westfield         42.12N 72.75W
09/06/2025                   Hampden            MA   Amateur Radio

            Video confirmation of wires down and on fire
            (relayed via amateur radio).

0257 PM     Tstm Wnd Dmg     Southampton             42.23N 72.73W
09/06/2025                   Hampshire          MA   Law Enforcement

            Route 10 closed due to downed trees (relayed
            via amateur radio).

0257 PM     Tstm Wnd Dmg     1 SSE Southampton       42.22N 72.73W
09/06/2025                   Hampshire          MA   Law Enforcement

            Multiple large trees down on power lines
            near Clark Street in Southampton (relayed
            via amateur radio).

0302 PM     Hail             1 SW South Hadley       42.26N 72.58W
09/06/2025  M0.75 Inch       Hampshire          MA   Amateur Radio

0303 PM     Hail             3 SW Chicopee           42.15N 72.61W
09/06/2025  M0.75 Inch       Hampden            MA   Amateur Radio

0310 PM     Tstm Wnd Gst     1 SE Granby             42.26N 72.52W
09/06/2025  M64 MPH          Hampshire          MA   Public

            public report relayed via amateur radio.

0325 PM     Hail             4 NW Ashburnham         42.68N 71.94W
09/06/2025  M1.00 Inch       Worcester          MA   Amateur Radio

&&

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
403 PM EDT Sat Sep 6 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0255 PM     Tstm Wnd Dmg     2 SW Northampton        42.30N 72.71W
09/06/2025                   Hampshire          MA   Fire Dept/Rescue

            Tree down on house (relayed via AR).

0305 PM     Tstm Wnd Dmg     1 SE Holyoke            42.20N 72.62W
09/06/2025                   Hampden            MA   Trained Spotter

            several large trees down on I-91 (relayed
            via AR).

0330 PM     Tstm Wnd Dmg     Warren                  42.21N 72.19W
09/06/2025                   Worcester          MA   Law Enforcement

            Tree down on a car on Nelson Street (relayed
            via AR).

0330 PM     Tstm Wnd Dmg     4 SSE Belchertown       42.22N 72.38W
09/06/2025                   Hampshire          MA   Law Enforcement

            several trees and power lines down (relayed
            via AR).

&&

Preliminary Local Storm Report
National Weather Service Boston/Norton MA
420 PM EDT Sat Sep 6 2025

..TIME...   ...EVENT...      ...CITY LOCATION...     ...LAT.LON...
..DATE...   ....MAG....      ..COUNTY LOCATION..ST.. ...SOURCE....
            ..REMARKS..

0405 PM     Tstm Wnd Dmg     1 NNW New Britain       41.69N 72.80W
09/06/2025                   Hartford           CT   Fire Dept/Rescue

            Power lines and tree down through a house
            (relayed via AR).

0406 PM     Tstm Wnd Dmg     1 N Paxton              42.33N 71.93W
09/06/2025                   Worcester          MA   Fire Dept/Rescue

            tree down on a house (relayed via AR).

&&