Severe Thunderstorm Warning 33, NWS Boston/Norton, MA

Area Forecast Discussion
National Weather Service Boston/Norton MA
251 PM EDT Thu Jul 3 2025

.SYNOPSIS...
Hot temperatures today will likely trigger a round of scattered
showers & t-storms between 4 and 10 PM, some of which may be
severe. Quiet for Independence Day heading into the weekend,
then heat and humidity kick up for Sunday and the start of next
week. Unsettled weather may make a return Tuesday into
Wednesday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Key Messages...

* Severe Thunderstorm Watch in effect for all of CT, RI, and MA
  (excluding the Cape & Islands).

* Hot and muggy this afternoon ahead of the main line of
  thunderstorms.

Temperatures keep climbing this afternoon, well into the upper
80s and even into the low 90s in some areas. Already seen some
early morning convection across northern MA, and expecting
another round of storms to develop later this afternoon in
western MA/northern CT. A low over Quebec is moving SE into New
Brunswick, pushing a cold front across New England this
afternoon. The cold front combined with a neutrally tilted mid-
level shortwave will provide plenty of forcing for thunderstorms
development. Dewpoints are in the 60s and PWATs are in the
1.25"-1.5" range this afternoon, so plenty of moisture. MUCAPE
remains near 1500 J/kg and mid-level lapse rates are also
remaining around 6.5 C/km. Given the relative strength of the
ingredients and how the morning has behaved, felt confident
collaborating with SPC to put out a Severe Thunderstorm Watch
for all of CT, RI, and MA (excluding the Cape and Islands).

While isolated thunderstorms can fire at any given time this
afternoon, expecting the main threat to move through from west
to east generally between 4 and 10 PM. While bulk shear values
are better than we saw on Tuesday (30-40 kts), a limiting factor
will be the amount of moisture and instability available, as
well as marginal surface convergence given winds veering to the
W/NW ahead of the mid level front. Even so, parameters are
favorable for at least a few isolated severe storms, the main
threats being damaging winds and large hail. Storms exit and die
down following sunset and loss of diurnal heating.

Post-FROPA, a cooler and drier airmass settles in. Dewpoints
drop into the 50s, allowing for overnight lows to drop into the
upper 50s and low 60s.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Key Messages...

* Dry & sunny for Independence Day.

Once the colder airmass moves into place overnight, we'll start
to see some drying and more pleasant weather. Friday should be
quite sunny, with temperatures in the low to mid 80s under a
high pressure.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages...

* Dry and sunny through the weekend.

* Heat and humidity increase Sunday into early next week.

* Unsettled weather returns around late Mon/Tue but low
  confidence in timing/location details.

The mid level trough finally exits east on Saturday with
ridging building in followed by a weak shortwave early next
week. This will pump up the heat and humidity, really starting
on Sunday when the 90s return and continuing until at least
Monday. Beyond that there is some uncertainty owing to the
timing of a frontal system which may bring down temperatures
while also introducing a chance for showers and thunderstorms as
early at late Monday. For now, best chance of unsettled weather
looks centered on Tuesday, which would bring down temperatures.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

18z TAF Update...

Today and tonight...High confidence except moderate confidence
on thunderstorm potential... areal coverage as well as timing.

VFR outside of any scattered t-storm threats after 18z into the
first half of the evening. Areal coverage and timing remains
uncertain with this activity...but a few strong t-storms are
possible which may contain locally strong wind gusts and hail
too. The greatest risk is across interior MA and CT terminals.
W winds generally 5-10 knots becoming more NW later tonight.

Independence Day...High confidence.

VFR. NW winds 5-10 kts at most terminals.

KBOS Terminal...High confidence in TAF. Main concern is the risk for
a t-storm in the vicinity of the terminal after 19z/20z into
the early evening hours.

KBDL Terminal...High confidence in TAF. Main concern is the risk for
a t-storm in the vicinity of the terminal after 18z/19z into
the early evening hours.

Outlook /Saturday through Tuesday/...

Saturday: VFR.

Saturday Night through Sunday Night: VFR. Breezy.

Monday: VFR. Breezy. Slight chance SHRA, slight chance TSRA.

Monday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, slight chance TSRA.

Tuesday: Breezy. Chance SHRA, chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Independence Day...High confidence.

Winds/seas stay below small craft advisory thresholds through
Friday. Winds will generally be in SW direction on the order of
7-15 knots before switching too a more NW direction tonight
behind the cold front.

Outlook /Saturday through Tuesday/...

Saturday through Saturday Night: Winds less than 25 kt.

Sunday through Sunday Night: Low risk for Small Craft Advisory
winds with gusts up to 30 kt. Areas of seas approaching 5 ft.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft.

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

Tuesday: Winds less than 25 kt. Chance of rain showers, slight
chance of thunderstorms.

&&

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

&&

SYNOPSIS...McMinn
NEAR TERM...McMinn
SHORT TERM...McMinn
LONG TERM...BW
AVIATION...McMinn/FT
MARINE...McMinn