712
FXUS61 KBOX 151144
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
744 AM EDT Tue Jul 15 2025

.SYNOPSIS...
Heat and humidity will build once again this week, peaking on
Wednesday, but possibly lasting into Thursday or Friday as high
pressure remains offshore. A cold front should bring showers
and thunderstorms Thursday and Friday before relief from the
heat arrives this weekend.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Messages:

 * Heat and humidity begin to build today.
 * Heat Advisory remains posted today through Thu.

Upper ridge builds off East Coast over next several days which
will pump increasing heat and humidity into region starting
today.

Prior to that, a band of light rain showers (more like
sprinkles) was working through SNE early this morning. This
activity is remains of yesterday`s convection to our west and
was located ahead of weakening cold front that will essentially
wash out over region today. Once this activity heads out to
sea, ridging and daytime heating will help erode low cloud
cover in place, though with persistent SW flow that will be
tougher to happen near Cape Cod and Islands.

Not seeing a lot of signals for showers/storms to develop this
afternoon despite decent surface-based instability up to 2500
J/kg. Aside from terrain or perhaps south coastal sea breeze,
there isn`t a good lifting mechanism available to generate
convection, so the thought it we could see a lone shower/storm
try to develop, but not much more than that especially given
rising heights aloft and axis of higher K-indices being
displaced offshore. CAMs seem to follow this thinking, even more
robust EMC RRFS. If anything does manage to develop, main
threat would be localized flooding rain given weak winds aloft
and plentiful moisture, but even that seems to be a stretch.

We should see another night of low clouds and patchy fog tonight,
especially near South Coast with persistent SW flow. Certainly
looks to be a warm and muggy night, especially within urban
centers.

&&

.SHORT TERM /WEDNESDAY/...
Key Messages:

 * Peak of heat and humidity Wed.

Upper ridge crests over SNE Wed with 590+ heights over region.
Looks to be peak of heat and humidity with heat index (what it
feels like) reaching 100F in many areas outside of higher
elevations and locations near South Coast. Despite heat and
humidity, we do not expect any showers or storms given strong
mid level cap shown on forecast soundings which will suppress
convective development.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Messages:

 * Heat and humidity persists into Thu or Fri with increasing
   chances of showers/storms.
 * Relief arrives this weekend.

We remain in hot/humid airmass through end of the week, awaiting
approach of mid level short wave and fairly strong cold front
which will eventually bring relief from the heat and humidity
this weekend. Seeing some timing differences among models with
respect to how quickly both of thee features come through. Slower
solutions would keep the heat and humidity going into Fri,
although more in way of cloud cover could keep us just shy of
Heat Advisory criteria. Faster approach means Thu would be focus
for showers/storms and most of the ML guidance supports this
idea with main risk of severe storms on that day (wind damage).
For what it`s worth, 00z GFS is even a little faster than that
and brings upper trough/front through Thu AM followed by drying
in afternoon. For now, forecast will show chances of showers/storms
in Thu/Fri timeframe and we will be able to nail down timing
better in later forecasts.

Front may eventually stall just south of New England later in
weekend and possibly return north again early next week, setting
stage for more showers/storms, but there`s more uncertainty in
how things play out.

&&

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

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

12z TAFs: Moderate confidence due to timing of low ceilings.

Improvement to VFR continuing this morning across the mainland
terminals, aside from the Cape where ceilings are still IFR.
Expected to continue improving this morning, but Cape Cod and
Island terminals may not reach VFR until 17-20z. IFR to LIFR
returns there around sunset this evening. VFR Wed.

S/SW winds 10kt or less through Wed, although sea breezes could
develop along E MA coast later this morning.

KBOS Terminal...Moderate confidence in TAF due to timing of
seabreeze.

KBDL Terminal...High confidence.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR. Chance SHRA, slight chance TSRA.

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

Thursday Night: VFR. Breezy. Slight chance SHRA.

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

Friday Night: VFR. Slight chance SHRA.

Saturday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

High confidence through end of the week.

Winds and seas stay below SCA through at least Wed as light SW
flow persists with high pressure building offshore. Approaching
cold front sometime Thu/Fri will bring tightening gradient which
could bring 25kt winds and/or 5 ft seas to at least waters E
and S of Cape Cod.

Main concern will be areas of fog, especially at night and into
morning, due to persistent SW winds through end of week.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. Slight chance of rain
showers, slight chance of thunderstorms.

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
showers, slight chance of thunderstorms.

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

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

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

Saturday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for
     CTZ002>004.
MA...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for
     MAZ003>007-010>021-026.
RI...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for
     RIZ001>007.
MARINE...None.

&&

$$

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