168
FXUS61 KBOX 101808
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
208 PM EDT Thu Jul 10 2025

.SYNOPSIS...

Seasonably warm and humid weather will remain in control of our
weather into the first half of next week. Although there
will be diurnally-driven shower and thunderstorm chances in
western MA and CT this weekend, most of eastern MA and RI should
remain dry under onshore flow. A frontal system on Monday
offers better chances at showers and thunderstorms across most
of Southern New England. Temperatures then warm up around the
middle of next week, but will have to monitor for possible
unsettled weather off the mid-Atlantic waters.

&&

.NEAR TERM /THROUGH TONIGHT/...

Key Points...

* Lingering showers towards the Cape and Islands dissipate by early
  evening

* A few showers/isolated t-storm or two also possible across the
  distant interior this evening...but otherwise dry tonight

* Areas of fog tonight some of which may become locally dense with
  low temps in the 60s

Details...

Tonight...

A few lingering showers are possible into early this evening towards
the Cape and Islands. Otherwise...enough diurnal heating and
marginal instability may generate a few showers and perhaps an
isolated t-storm or two across the distant interior into this
evening. Greatest risk for this will be near and west of the CT
River.

Otherwise...moist low level northeast flow coupled with dewpoints in
the 60s will result in widespread low clouds persisting tonight.
This may also lead to areas of fog...which could be locally dense in
spots especially near the coast and Worcester Hills. Low temps
tonight will be in the 60s.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...

Key Points...

* Warm & humid Fri with partial sunshine developing Fri

* Highs in the 80s Fri away from the immediate coast

* A few strong to marginally severe t-storms possible across
  the interior Fri PM with localized torrential rainfall

Details...

Friday...

The low clouds and fog should gradually burn off Friday morning and
especially by afternoon with the help of the strong July sun angle.
With at least partial sunshine developing...high temperatures should
reach into the 80s inland from the immediate coast. Dewpoints in the
upper 60s to near 70 will also result in humid conditions. On the
immediate coast...sea breezes will keep high temps in the 75 to 80
degree range but it still will be humid.

The other issue will be the risk for a few strong to marginally
severe t-storms Fri afternoon and evening across the interior. It
does look like we should generate modest instability in the 1500 to
2000 J/KG range with marginal shear on the order of 25 to 30 knots.
Poor mid level lapse rates and limited upper level support will
temper this potential. That being said...a few strong to marginally
severe t-storms are possible Fri afternoon/early evening but
certainly not expecting a severe weather outbreak. Main risk would
be localized strong to damaging wind gusts with localized torrential
rainfall. Dry weather should prevail across most of the coastal
plain with the main instability/forcing focused to the west.

Friday night...

Any widely scattered convection should come to an end Fri evening.
Otherwise...dry weather is in store for Fri night with low temps in
the 60s.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...

Key Messages:

* Drier with onshore flow in eastern portion of Southern New England
  this weekend, with diurnally-driven showers/t-storms possible each
  day this weekend in western MA and CT. Still rather humid but
  temps around or slightly cooler than seasonable.

* Better chance at more widespread showers/t-storms Monday, although
  severe weather potential looks limited.

* Turning very warm to hot around mid next week, but monitoring
  possible unsettled weather off the mid-Atlantic coast.

Details:

This Weekend:

Overall a pretty similar weather pattern anticipated for this
weekend. Sfc high pressure in the Gulf of Maine forces a period of
onshore ESE flow, while a weakness in the 500 mb height field lends
itself to more unsettled conditions over distant interior Southern
New England. While most of central and eastern MA and RI should end
up seeing drier conditions than not, a daily (mainly mid-aftn to
early evening) risk for scattered slow-moving showers or
thunderstorms are possible for western MA and CT in vicinity of the
weak upper trough and associated with weak upslope flow. With weak
flow aloft and CAPE values around 1500 J/kg, probably not looking at
severe weather with any storms, but lightning and slow-moving
downpours are possible in any storm which develops. Daily evening to
overnight risk for patchy radiation fog and stratus as well. Highs
low to mid 80s (mid/upper 70s Cape and Islands with onshore flow,
with mid/upper 80s for interior Southern New England.

Monday:

Unfortunately Monday offers a better chance at showers and
thunderstorms across a wider portion of Southern New England, as a
stronger shortwave trough in midlevels and an associated sfc front
cross the area during the afternoon to early evening. Wind fields
aloft at a little stronger than during the weekend, though they`re
still better characterized as weak, and instability values are also
on the lower side. Wouldn`t rule out a stronger cell or two but
thinking any storms would be more garden-variety than otherwise.
Highs are generally similar in the mid 80s and still rather humid.

Tuesday through Thursday:

Some uncertainty in the specific details in this period with respect
to the anticipated weather pattern. More specifically the GFS shows
an amplifying ridge over the OH Valley moving eastward. On the other
hand, the ECMWF and the Canadian GEM are weaker/slower to advance
this ridge eastward, instead favoring a weakness in the height
field/troughiness along the mid-Atlantic/northeast US coastline. A
minority of the ECMWF/GEM members even show some diffuse area of
disturbed weather moving northward from the mid-Atlantic/Carolinas.
Temperatures stand to be quite a bit warmer than the weekend/Monday
and it will also be quite a bit more humid too, but there is more
uncertainty on cloud cover/rain chances in this period given the
differences in ensembles. Because of that uncertainty, didn`t really
stray far from the NationalBlend. Highs in the upper 80s to
lower 90s.

&&

.AVIATION /18Z THURSDAY THROUGH MONDAY/...

Forecaster Confidence Levels...

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

18z TAF Update...

This afternoon & tonight...High confidence.

A few lingering showers may persist into early evening near the Cape
and Islands. We may also see a few spot showers/isolated t-storms
into the evening across the distant interior. Overall though the
weather should remain dry for many locations.

IFR with some MVFR conditions across the interior this afternoon
will lower back to mainly IFR/LIFR this evening with a cooling
boundary layer. We also will need to watch for the development of
fog...some of which may become locally dense near the coast and
Worcester Hills but that remains more uncertain than the lower
ceilings. Light/Calm winds.

Friday...High confidence in trends but lower confidence in timing.

The low clouds and fog patches should burn off in most locations by
Friday afternoon allowing mainly VFR conditions to develop. A few
strong thunderstorms will be possible Fri afternoon and early
evening across parts of interior MA & CT...but it should remain dry
near the coast. Winds will mainly be light from an ESE/SE direction.

Friday night...Moderate confidence.

Any isolated convection across the interior would wind down Fri
evening. Otherwise...VFR conditions dominate in the evening but may
see some MVFR-IFR conditions develop overnight with the lingering
low level moisture. Light S winds.

KBOS Terminal...High confidence in low ceilings with more
uncertainty on how much fog develops tonight.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday through Monday/...

Saturday: VFR. Slight chance SHRA, slight chance TSRA.

Saturday Night through Sunday: Mainly VFR, with local MVFR
possible.

Sunday Night: VFR. Slight chance SHRA.

Monday: VFR. Chance SHRA, chance TSRA.

&&

.MARINE...

Forecaster Confidence Levels...

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

Tonight through Friday night...High confidence.

Weak pressure gradient will keep winds/seas below small craft
advisory thresholds through Friday night. Main concern for mariners
will be areas of fog...some of which may be locally dense
particularly tonight into mid-morning Friday.

Outlook /Saturday through Monday/...

Saturday through Monday: Winds less than 25 kt.

&&

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

&&

$$

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