675
FXUS61 KBOX 251921
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
321 PM EDT Wed Jun 25 2025

.SYNOPSIS...
Turning cooler Thursday through Saturday, then warming Sunday
into early next week, with daily chances of showers and
thunderstorms.

&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...
Key Messages:


* Widely scattered thunderstorms wind down with the loss of daytime
  heating

* Temperatures and dewpoints rapidly fall overnight behind backdoor
  cold front

Relief from excessive heat and humidity is well on its way as a cold
front currently located across portions of central New Hampshire
continues to move south. A few widely scattered showers and
thunderstorms will continue over the next few hours. The best chance
of this activity will be across portions of central and eastern
Massachusetts where the seabreeze boundary will act as a focus for
activity. Generally expecting storms to remain below severe limits
as MLCAPE values wane behind the front. Falling temperatures and
dewpoints will allow the Heat Advisory in effect for the majority of
our CWA except the Worcester Hills and coastal areas to expire
at 7 pm. Outside of the lingering heat-related statements, the
Rhode Island Department of Environmental Management has issued
an Air Quality Action Day for Ground Level Ozone, that will
remain in effect through 11pm EDT this evening. An Air Quality
Action day means that Ground Level Ozone concentrations within
the region may approach or exceed unhealthy standards.

&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH 6 PM THURSDAY/...
Key Messages:

* Much cooler behind backdoor cold front
* Weak upper disturbance and WAA brings widely scattered showers

Temperatures on Thursday will be about 25 to 30 degrees lower than
today as southward moving high pressure allows for an easterly flow.
Highs will struggle to get out of the upper 60s and lower 70s for
much of the region. In terms of precipitation, high-res guidance is
advertising a band of showers across much of the region. These
showers are due to upper mid-level WAA around the periphery of the
backdoor cold front. Not expecting a washout, but low clouds and
cooler temps will make for a somewhat gloomy day on Thursday. Cool
and cloudy conditions continue Thursday night with lows falling into
the upper 50s and lower 60s regionwide.

&&

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

Key Messages...

* Significantly cooler weather continues Friday and into the weekend
  before temps return to the upper 80s and low 90s early next week.

* Daily chances of rain and some thunderstorms possible each day
  through Sunday, drier Monday, then more unsettled weather
  possible around Tuesday.

Relief from the heat continues Friday into the weekend with a
flattening of the ridge and surface high pressure expanding south
from Canada. Cool northeast/onshore flow will be directed off the
Atlantic over southern New England. This results in high
temperatures about 30 degrees colder than we experienced earlier in
the week, below normal for late June. Highs on Friday and Saturday
will remain in the low to mid 70s, helped by plenty of cloud cover.
Things begin to change by Sunday and beyond as a trough of low
pressure approaches, turning winds back to the southwest. This
advects warmer air north as highs return to the mid to upper 80s Mon-
Wed. At this point ensembles indicate only a very slight (<20%)
chance of seeing 90s again. Stay tuned.

As for rain chances, we`ll see periods of wet weather return to the
forecast Friday and through the weekend. Flow will be quasi-zonal ,
lacking any big significant storm systems. Moreso we`ll see several
weak disturbances moving through between Thursday and early next
week. The best chance of seeing at least a tenth of an inch of rain
in any 24 hour period according to ensemble guidance is Saturday (of
course) with both the EPS and GEFS showing a 70%+ chance, greatest
further north, less to the south. There remains a decent
discrepancy in the placement of the front Saturday which will
determine how wet it may be, but should see increasing
confidence over the next 24 hours. Brief ridging follows Monday
which keeps things dry before another more robust shortwave
toward Tuesday brings renewed rain and thunderstorm chances. &&

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

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

18z Update

Today: Moderate Confidence.

VFR. Sea breeze has made it to BOS and much of coastal
Massachusetts. Wind speeds are between 8 and 12 knots. Opted to
downgrade the probs to -SHRA as convection that has formed has
been shallow and is producing weak returns.

Tonight: High Confidence.

VFR. Shower chances are highest across the southern coastal
waters. Wind shifts to the northeast, less than 10 knots across
the interior and 10 to 15 knots across eastern Massachusetts and
Rhode Island.

Thursday: Moderate Confidence.

VFR to MVFR. Periods of showers are possible, though confidence
is lower in exact location and timing. Northeast to east winds
around 10 knots.

KBOS Terminal...Moderate confidence in TAF.

VFR with winds turning ENE this morning and staying there for
much the TAF period. Chance for thunderstorms this afternoon
between 17-23z.

KBDL Terminal...Moderate confidence in TAF.

VFR with light winds today. Chance for thunderstorms this
afternoon between 17z-23z.

Outlook /Thursday Night through Monday/...

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

Friday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA.

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

Saturday: MVFR/IFR conditions possible. Breezy. Chance SHRA,
chance TSRA.

Saturday Night: MVFR/IFR conditions possible. Chance SHRA,
slight chance TSRA.

Sunday: Mainly VFR, with local IFR possible. Slight chance
SHRA, slight chance TSRA.

Sunday Night: Mainly VFR, with local IFR possible.

Monday: Slight chance SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today and Thursday: High Confidence.

Weak cold front approaches from the north, increasing clouds and a
few pop-up showers and thunderstorms. Northern waters have northerly
winds while the southerly waters have a southerly wind. Wind becomes
northeast for all waters Wednesday night and increase to 10 to 15
knots. Seas are less than 2 feet. Cold front settles south of the
southern outer waters with east/northeast winds 10 to 15 knots and
gusting to 20 knots. Seas building from the south 3 to 4 feet.
Outlook /Thursday Night through Monday/...

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

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

Friday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, slight chance of thunderstorms.

Saturday: Winds less than 25 kt. Seas up to 5 ft. Chance of
rain showers, slight chance of thunderstorms.

Saturday Night: Winds less than 25 kt. Local rough seas. Chance
of rain showers, chance of thunderstorms.

Sunday: Winds less than 25 kt. Local rough seas. Chance of rain
showers, slight chance of thunderstorms.

Sunday Night: Winds less than 25 kt. Seas up to 5 ft.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 7 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 7 PM EDT this evening for MAZ003-005-006-
     010>014-017-018-020-021-026.
RI...Heat Advisory until 7 PM EDT this evening for RIZ001>007.
     Air Quality Alert until 11 PM EDT this evening for RIZ006>008.
MARINE...None.

&&

$$

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