765
FXUS61 KBOX 311836
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
236 PM EDT Thu Jul 31 2025

.SYNOPSIS...
Much cooler conditions are expected into Friday, with the
potential for heavy rain and localized flooding tonight across
portions of interior southern New England. An extended stretch
of dry weather then develops for this weekend into early next
week. Temperatures are seasonable with lower humidity levels
this weekend, but with a warming trend for early next week.

&&

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

* Widespread showers and isolated t-storms with locally heavy
  rainfall, initially focused across interior MA will shift to the
  coastal plain tonight

* Heaviest rainfall axis expected to be across interior MA into CT
  where localized amounts up to 3-4 inches possible

Most widespread rainfall across SNE is focused across interior MA
into NW CT assocd with mid level forcing north of the low-mid level
front. We are seeing some scattered convection develop further to
the south along the northern edge of the surface-based instability
gradient. More organized storms and very heavy rainfall rates are
ongoing across eastern PA to NJ, but this is expected to remain to
the south where best instability and forcing is expected. A few
storms with heavier rainfall rates will be possible through the
afternoon south of the MA Pike, but instability shifts to the south
this evening. This leaves the mid level forcing as the primary
driver of rainfall through tonight. SNE is within the higher
moisture axis with PWATs 1.5-2 inches so heavy rainfall is expected
but rates will be manageable given lack of instability. Still, very
efficient warm rainfall processes will be ongoing with deep warm
cloud depths 12-14k ft in place. Timing wise, the rain area will
initially be focused across interior MA into NW CT into this evening
with scattered convection further south, then it shifts SE to the
coastal plain tonight as the 850 mb front shifts south across SNE
with PWAT axis becoming focused near the south coast overnight.
Drier air begins to move into northern MA where rain will taper off
late tonight.

Rainfall totals of 1-2 inches is expected across much of SNE,
with less near the south coast. But localized amounts up to 3-4
inches are possible from central/W MA into NW CT where longer
duration of mid level frontogenesis is expected. Areas of urban
and poor drainage street flooding is expected, but given that
the heavier amounts will occur over a 12-18 hr period any
flooding impacts should be minor. We will keep the flood watch
for CT but not expand it into MA.

&&

.SHORT TERM /FRIDAY THROUGH FRIDAY NIGHT/...
Key Messages:

* Showers end during the morning near the south coast with sunshine
  developing from NW to SE during the afternoon. Below normal temps.

* Clearing and chilly Fri night with lows in the 50s

Drier air will be moving southward into SNE by Fri morning with
PWATs falling through the day. Rain will have ended across much of
the interior by morning, with showers lingering near the south
coast. However, expect rain to end here through the morning with
mainly dry conditions in the afternoon. Modest low level jet will
result in gusty NE winds, especially near the coast. The wind and
rain here in the morning with temps in the 60s will make it feel on
the raw side.

Drier air will continue to move southward into the region which will
allow sunshine to develop from NW to SE during the afternoon. Highs
will recover into the low-mid 70s in the interior, but closer to 70
across RI and SE MA where sunshine will be later arriving.

Clearing skies Fri night as high pres builds in from the west, but
still enough gradient for a modest N breeze near the coast. Chilly
night with lows ranging through the 50s.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages:

* Several days of dry and seasonable weather starting this
  weekend.

Upper flow should feature broad trough over Northeast starting over
the weekend and into much of next week, which will allow for a dry
and seasonable weather pattern to prevail. We start to see more
uncertainty toward the end of the week, when subtropical ridge
should build off southeast coast and dig deeper trough over
eastern Great Lakes and Ohio Valley. While we don`t see return
of hot and humid conditions, it may promote moisture feed up
East Coast and could bring our next round of rainfall,
especially if we see surface low development near mid Atlantic
coast.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

18Z Update: Widespread convection has developed from SW to NE
roughly from N CT through to NE MA. Convection and low clouds
have brought MVFR and IFR conditions to much of the airspace.
IFR conditions will be favored under areas of heavier rain while
MVFR will be favored elsewhere.


Otherwise, the previous discussion remains in good shape.

-----------------------------------------------------------

Tonight...High confidence.

MVFR and IFR most of tonight in widespread rainfall. Risk for
thunderstorms diminishes after sunset, but is not an
impossibility overnight, especially south of the Mass Pike.
Becoming breezy late tonight.

Friday...High confidence in trends. Moderate confidence in
timing. Winds diminishing into the afternoon.

MVFR/IFR improving to VFR from NW to SE during the day.

KBOS terminal...Moderate confidence in TAF, mainly due to timing.

KBDL terminal...Moderate confidence in TAF, mainly due to timing.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Breezy.

Saturday Night: VFR.

Sunday through Sunday Night: VFR. Breezy.

Monday through Monday Night: VFR.

Tuesday:

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Friday night...High confidence.

Increasing NE winds developing tonight into Fri with gusts to 30 kt
as low level jet develops. Gusty winds will slowly subside across NE
MA waters later in the day, but this will take until late Fri night
over southern waters.

Outlook /Saturday through Tuesday/...

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

Saturday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Sunday through Tuesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Flood Watch through Friday morning for CTZ002>004.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 PM this evening to 2 AM EDT
     Saturday for ANZ231>235-237.
     Small Craft Advisory from 2 AM to 8 PM EDT Friday for ANZ236-
     251.
     Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Saturday for ANZ250-254>256.

&&

$$

SYNOPSIS...KJC/JWD
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...JWD
AVIATION...FT/JWD
MARINE...KJC/JWD