314
FXUS61 KBOX 121132
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
732 AM EDT Sat Jul 12 2025

.SYNOPSIS...
Seasonably warm and humid conditions continue this weekend.
Chance for showers and thunderstorms across the interior today,
then trending drier for Sunday. A better chance at showers and
thunderstorms then exists on Monday as a frontal system moves
through. Increasing heat and humidity around the middle of next
week, which then looks to break around Friday as a cold front
brings risk for showers and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Points

*Continued warm and humid conditions
*Isolated showers and thunderstorms are possible once again across
the  interior

Very little change in airmass on Saturday as high pressure remains
parked just off shore. Surface winds turn more ESE as a result of
the high pressure, but with dry air offshore, not expecting low
clouds and fog to persist all day, with the exception over the Cape
and Islands. High temperatures today top out in the low to mid-80s
with partial sunshine.  Mid-level flow begins to turn more SW late
across western MA and into NY and VT. This will help establish a
weak convergence boundary that could bring Isolated showers and
thunderstorms to the interior. 00z Hi-res guidance has trended this
activity further west, remaining in NY and VT.  With 1000-1500 J/kg
of MLCAPE and a relatively light cap, I wouldn`t be surprised
to see some thunderstorms across the western interior near the
high terrain. The severe threat still appears limited, with
little to no shear and mid-level lapse rates of around 5 C/km.
PWATS are a bit higher today compared to yesterday, around 1.5
inches. Some cells produced 2-4 inches of rain in a relatively
short period yesterday, prompting a couple of flash flood
warnings. Assuming storms form in the western interior today,
there is a risk for more heavy rain and flash flooding. 00z HREF
highlights much of the western interior with a 30-50% chance to
receive 1 inch of rain in 3 hours and a 10% chance to receive 3
inches of rain in 3 hours

&&

.SHORT TERM /SUNDAY/...
Key Points

*Mild with fog again tonight
*Dry with seasonably warm and humid conditions on Sunday

Tonight:

Another mild night with low temperatures bounded by dewpoints in the
low to mid-60s.  More low clouds and fog form shortly after sunset
again with light ESE onshore flow.

Sunday:

Very little change in airmass on Sunday as high pressure remains
offshore over the Gulf of Maine and a mid-level ridge over the
region.  High temperatures once again warm into the low to mid-80s,
with dewpoints still in the mid-to-upper 60s.  Storm chances are
lower Sunday as the axis of instability moves further north with the
convergence boundary.  This leaves SNE capped under the subsidence
inversion from the mid-level ridge.  Skies turn mostly sunny after
the morning fog and stratus burn off.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...
Key Messages:


* Better chance at more widespread showers/t-storms Monday, although
  lower instability values should limit potency of these
  showers/storms.

* Very warm to hot during the middle of next week, with elevated
  heat indices around 95-100F.

* Cold front Friday brings a break from the heat and humidity, but
  also a risk for thunderstorms.

Details:


Monday:

It still looks like Monday offers a better chance at showers and
thunderstorms across a wider portion of Southern New England than
compared to the weekend, as a stronger shortwave trough in midlevels
and an associated sfc front cross the area during the afternoon to
early evening. Still pretty weak wind fields overall, albeit a touch
stronger than prior days. Instability values are also still 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 middle 80s, but will be accompanied by
increased humidity levels.

Tuesday through Thursday:

Warming temperatures and increased levels of humidity are
anticipated for this period, as shortwave ridging aloft builds over
and just east of Southern New England. This should bring increasing
heat indices to elevated levels, in particular for Wed and Thurs.
Both days could feature heat indices approaching Advisory thresholds
in the mid 90s to low 100s, highest in the CT and Merrimack Valleys.
High temps stand to reach into the upper 80s to mid 90s away from
the coast.

It looks as though this period is generally dry with subsidence
aloft governing our weather. That said, there are still a smaller
minority of GEPS/EPS members which show some unsettled weather
emanating from the mid-Atlantic offshore waters/Gulfstream current
moving off towards the NE. Were this to transpire, it could bring a
risk for cloudiness and some showers. With fewer ensemble members
offering this potential, this wetter outcome isn`t currently
reflected in the forecast, but may need to be re-considered if
there are more ensemble members which show rainier conditions.

Friday:

Friday could feature another day of elevated heat and humidity, but
most of the ensemble means show an approaching cold front with
higher-end Chance PoPs for showers and thunderstorms coming in
during the afternoon. Flow aloft is seasonably strong and could
point to a few stronger storms around as the front sags southward
but still enough time to drill into those details in the coming days
ahead.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

12z TAF Update:

Saturday: Moderate confidence.

With little change to the weather pattern, expecting low stratus
and fog to lift and burn off between 12-15z with the exception
of the Cape and Islands where CIGS may remain low all day.

VFR with pockets of MVFR again with lingering low level
moisture. Chance for scattered showers and thunderstorms again
this afternoon, although recent guidance has trended the
activity further west. Went with prob30 for TSRA at western
terminals for now, but future shifts may consider removing.


Saturday Night: Moderate confidence.

More IFR/LIFR Stratus builds north under light ESE flow.

KBOS Terminal...High confidence in TAF.

IFR/LIFR CIGS through about 15z again, then VFR/MVFR through the
afternoon. Low stratus deck likely again tonight.

KBDL Terminal...High confidence in TAF.

MVFR/IFR through about 13z, then CIGS gradually improve to VFR.
Chance for thunderstorms again late this afternoon/evening, but
the threat has trended further west.

Outlook /Sunday Night through Wednesday/...

Sunday Night: Mainly VFR, with local IFR possible.

Monday: Mainly VFR, with local MVFR possible. Chance SHRA,
chance TSRA.

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

Tuesday through Wednesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Sunday...High confidence.

Weak pressure gradient will keep winds/seas below small craft
advisory thresholds through Sunday: seas 2-4 ft with E winds
over the southern waters and SE winds over the eastern waters up
to 15 kts during the afternoon hours, remaining light in the
overnight hours. Main concern for mariners will be areas of fog
tonight that may redevelop Saturday night.

Outlook /Sunday Night through Wednesday/...

Winds less than 25 kt.

&&

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

&&

$$

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