157
FXUS61 KBOX 021832
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
232 PM EDT Wed Jul 2 2025

.SYNOPSIS...

Dry and pleasant weather is in store for the region tonight. Very
warm to hot temperatures on Thursday will likely trigger a round of
scattered showers & t-storm roughly in the 2-10 PM time range.
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 /THROUGH TONIGHT/...

Key Messages...

* Low clouds and fog formation confined to mainly immediate south
  coast, Cape and Islands tonight

* Dry and pleasant tonight with lows in the 60 to 70 degree range

Details...

Tonight...

Shortwave energy will continue to move east and further away from
the region tonight. This will take a lot of the remaining mid level
cloud deck with it. The only issue for tonight is for the re-
development of more low clouds and fog near the immediate south
coast, Cape and Islands. The surface low level flow is veered
out...so thinking this low cloud/fog threat will not make it much
further north than the immediate south coast and therefore only
impact a very limited area in our CWA. Overnight low temps may range
from near 60 in the normally coolest outlying locations to around 70
in the Urban Heat Island of Boston. So most locations will see
overnight lows bottom out in the 60s.

&&

.SHORT TERM /THURSDAY THROUGH THURSDAY NIGHT/...

Key Messages...

* Very warm to hot on Thu with highs mainly in the upper 80s to near
  90 but not as humid as the last few days

* A few severe thunderstorms possible Thu between 2 & 10 pm with the
  greatest risk across interior MA & CT

* Drier & cooler later Thu night with lows in the 55-65 degree range

Details...

Thursday and Thursday night...

A very warm to hot day is on tap for Thursday ahead of an
approaching shortwave trough. Veered out low level flow and plenty
of sunshine will allow dewpoints to mix out a bit and allow highs to
reach the upper 80s to near 90 in many locations. Westerly flow
though will result in less humidity than the past couple of
days...but it still will be very warm to hot afternoon.

The main concern though revolves around the potential for a few
severe thunderstorms Thu PM...mainly in the 2-10 pm time frame with
the best chance across interior MA & CT closer to the main
shortwave/dynamics. A fairly impressive shortwave trough aloft
approaches the region Thu afternoon/evening with height falls and a
500T dropping into the -12C/-13C range. This cold pool aloft will
assist in creating modest mid level lapse rates on the order of 6.5
C/KM. Instability will not be crazy on Thu...but given the cold pool
aloft surface Capes in the 750 to 1500 J/KG range are expected. In
addition...0-6 KM shear values on the order of 30 to 40 knots with
the strongest of those wind fields across interior MA and CT.

This ingredients above are supportive for the potential for a few
severe thunderstorms Thu afternoon into the first half of the
evening with the greatest risk across interior MA and CT. Main
threats will be locally damaging wind gusts given the potential for
rather large T/Td spreads and steep low level lapse rates. In
addition...hail will also be a concern given the cold pool aloft and
adequate shear. This is also supported by a lot of the machine
learning guidance including the CSU, Nadocast and HRRR Neural
network which also show the greatest risk for this across interior
MA and CT. That being said...there are some limiting factors too.
The instability is rather marginal and surface winds are veered out
which will limit potential convergence. This might be why a lot of
the CAMs limit the areal coverage of the activity.

So in a nutshell...while this does not look like a widespread severe
weather outbreak given limited low level convergence the risk for a
few severe thunderstorms exists. Interior MA and CT may have the
greatest risk being closer to the dynamics/cold pool aloft and that
is also indicated with the machine learning guidance.

The activity should wind down by the second half of Thu evening as
the instability wanes with the loss of diurnal heating.
Otherwise...a drier WNW flow of air works into the region Thu night
behind the cold front. Overnight lows should drop into the middle to
upper 50s in the outlying locations to between 60 and 65 in the
urban centers.

&&

.LONG TERM /FRIDAY THROUGH TUESDAY/...

Key Messages:

* Dry and sunny for Independence Day heading into the weekend

* Summer heat and humidity Sunday into the start of next week

* Possibly unsettled weather returns Tuesday/Wednesday

Details...

The trough responsible for Thursday`s expected unsettled conditions
moves over New England and off to the east Friday. Temperatures
aloft will be slightly cooler as this trough makes its exit,
remaining under 20C at 925 mb. Highs for Friday are expected to be
in the low to mid 80s across southern New England. Quiet weather
will prevail for Independence Day heading into the weekend as
surface high pressure builds in. Drier air also moves in over the
region, which will bring a warm and less humid start to the weekend.

More humid conditions move in going into Sunday and the start of the
week as flow aloft shifts more SW and winds at the surface become
more S. Temperatures at 925 mb increase to around +25C during the
afternoons of Sunday and Monday; ensembles have probabilities at or
above 50 percent of temperatures greater than 90F across eastern MA
into RI Sunday, then across all of southern New England Monday
(probs also increase then as well compared to Sunday). Not much
relief can be expected overnight either, with lows in the upper 60s
and low 70s.

The chance for some unsettled weather returns Tuesday into Wednesday
with the arrival of a frontal system. It`s a bit far out to
determine the finer details of what to expect in terms of showers or
storms, but ensemble mean PWAT values approaching 2" may signal the
chance for possible downpours over the region. Whether these may be
widespread or isolated is still unknown.

&&

.AVIATION /19Z WEDNESDAY THROUGH SUNDAY/...

Forecaster Confidence Levels...

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

18z TAF Update...

Tonight...High confidence.

VFR conditions should persist tonight except near the immediate
south coast, Cape, and Islands where some IFR-LIFR conditions in low
clouds and fog may re-develop with the cooling boundary layer.
However...SW flow should confine this risk to the very immediate
south coast. Light SW winds.

Thursday and Thursday night...High confidence except moderate
confidence on thunderstorm potential areal coverage as well as
timing.

VFR conditions should dominate Thu into Thu night 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. That being said...this
activity will likely be more hit or miss type of stuff with the
greatest risk across interior MA and CT. W winds generally 5-10
knots becoming more NW later Thu night.

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

Outlook /Friday through Sunday/...

Thursday Night through Saturday Night: VFR.

Sunday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight through Thursday night...High confidence.

The pressure gradient will be weak enough to keep winds/seas below
small craft advisory thresholds through Thu night. The main concern
for mariners will be areas of fog redeveloping mainly across our
southern waters...which may become locally dense later tonight into
early Thu morning. Winds will generally be in SW direction on the
order of 7-15 knots tonight and Thu before switching too a more NW
direction Thu night behind the cold front.

Outlook /Friday through Sunday/...

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

Independence Day through Saturday Night: Winds less than 25 kt.

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 30 kt. Seas locally approaching 5 ft.

&&

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

&&

$$

SYNOPSIS...Frank/Hrencecin
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...Hrencecin
AVIATION...Frank/Hrencecin
MARINE...Frank/Hrencecin