457
FXUS61 KBOX 060758
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
358 AM EDT Sat Sep 6 2025

.SYNOPSIS...
A warm and humid day is on tap for today ahead of an approaching
cold front. This front will bring scattered severe thunderstorms
with localized torrential rainfall this afternoon and evening across
interior southern New England. This activity will weaken some on
approach the Boston to Providence corridor this evening. However, an
anafrontal wave will bring a period of widespread showers Sunday
morning which may linger int the afternoon towards the coast.
Otherwise...much of the work week looks dry and very pleasant
outside the risk for a few brief showers around mid-week.

&&

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

* Quiet morning across the region, becoming warm and humid, which
  gives way to an afternoon of strong and severe thunderstorms
  across interior southern New England. Storms may produce damaging
  straight-line winds, hail, torrential downpours, lightning, and
  cannot rule out the risk of tornadoes.

* Storms initialize around lunchtime in eastern New York and far
  western areas of southern New England, continues through the late
  afternoon. Scattered storms are expected to weaken as the cold
  front moves east towards the I-95 corridor, where much of the
  daylight hours are likely dry.

* Anafrontal wave brings continued showers into Sunday morning.

The bottom line up front, we are anticipating an active afternoon as
a robust cold front moves through New England, with the potential of
multiple hazards from scattered strong to severe thunderstorms. Do
not let the quiet morning lull you into a sense of complacency,
especially those that are northwest of an arbitrary line from
Hartford to Worcester to Lowell, where there is the greatest
potential for thunderstorms to be strong and become severe, between
12pm to 8pm. Areas that are east will have lower chance of severe
storms, but cannot rule out a few thunderstorm nearing the Boston to
Providence corridor between 7pm and 11pm, while southeast
Massachusetts perhaps gets a few rumbles of thunder. Additionally,
for eastern Massachusetts and Rhode Island it is likely to remain
rain-free through the daylight hours. While a rouge storm could
develop well out ahead of the front this is a low probability.

No surprise that this morning is noticeably warmer and more humid,
as a result have some low stratus across the region. Will say, the
guidance has not done well with resolving the extend of these clouds
with only a small area of stratus with ~500 foot ceilings across
parts of central southern New England. Though, high clouds are
filtering into New York and northern New England, ahead of the
approaching cold front. You might be thinking, why is this
impactful? Well, if we are able to keep the extent of the junky low
clouds away it is possible CAPE values this afternoon could be
greater, leading to more robust storms. And with temperatures
expected to reach into the 80s and dew point on either side of 70F
any storm the develops will have plenty of energy to tap into.

Overnight there were no significant changes to either SPC or WPC
outlook for this afternoon. SPC maintained it`s `Slight Risk` which
was issued Friday across interior southern New England. While there
was not much changed for our CWA, WPC did introduce a `Slight Risk`
of excessive rainfall into southwestern Connecticut, but kept the
original `Marginal Risk` footprint west of I-95.

Okay, let`s break down conditions for this afternoon:

* Lift: A mid-level trough is located over northern Great Lakes and
  sends robust 850mb shortwave into western New England, with a
  strong surface cold front.

* Instability: Forecast values between 1,500 and 2,000 J/kg. With an
  upper limit based off the HREF of 2,500 J/kg.

* Kinematic: This varies depending on which guidance source you are
  looking at, but consensus is between 45-60 knots of 0-6km shear.
  The SREF backs these impressive values with probabilites of 0-6km
  shear exceeding 50 knots at 50-70% across interior southern New
  England. Finally, the values for low-level helicity are equally as
  impressive with forecast values 100-150 m2/s2. There are even some
  outliers that have values nearing 200 units. Pretty impressive by
  southern New England standards.

* Moisture: PWATs are on the rise, increasing this afternoon to 1.6"
  and 1.8", not out of the question some areas approach 2.0" for
  central and western Connecticut, and western Massachusetts. These
  values are ~2 standard deviations above normal and with warm cloud
  layer ~10/12,000 feet, will have efficient rain makers. While it is
  a low probability, there is roughly a 10% chance of 2-3" of rain
  to fall within a 3 hour window across out southwest CWA border in
  Connecticut and Massachusetts.

* Hazards: Damaging straight-lined winds, hail, localized urban and
  poor drainage flash flooding, frequent lightning, and a low chance
  of tornadoes. Want to reiterate, we expect those hazards for
  interior southern New England, because storms are expect to weaken
  as the cold front moves east towards the Boston to Providence
  corridor.

* Timing: Storms initialize between 12-2pm across eastern New
  York and western areas of southern New England. There after is
  prime time for storms to build over, 2-6pm, for storms to
  develop over interior southern New England, but are expected
  to weaken as the line shifts to the I-95 corridor between
  7-10pm.

Whether you are heading to an outdoor event or hanging around the
house, today is one of those days to remain weather aware, and have
multiple ways of receiving weather alerts (cell phone notifications,
NOAA Weather Radio, and broadcast meteorologists).

Thankfully it looks like storms will be quick to wind down after
sunset. Expecting rain showers to continue especially across eastern
portions of the CWA tonight into Sunday. High res guidance suggests
an anafrontal wave develops during the predawn hours Sunday morning.
The wave could help to focus more of a steady rain mainly southeast
of I-95.

&&

.SHORT TERM /SUNDAY THROUGH SUNDAY NIGHT/...
Key Messages:
* Cooler with showers Sun am, which linger into afternoon on coast

Sunday...

An anafrontal wave will result in a wet Sunday morning for much of
southern New England given persistent southwest flow aloft. We still
need to sort out the axis of the most significant rain...but there
is often a narrow area that can receive quite the soaking in these
setups. Some elevated instability around too...so there will be an
isolated t-storm risk in the morning especially southeast of I-95.
We should see things dry out across the interior Sunday
afternoon...but showers may linger into the afternoon along and
southeast of the I-95 corridor. High temps will probably be held in
the middle 60s to the lower 70s given the clouds and rain.

&&

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

* Mainly dry/pleasant for much of next week...cool nights/mild days

* Offshore low may briefly graze the coast with a few showers Wed

Monday through Friday...

Dry/very pleasant weather is in store for much of the upcoming work
week...outside of an offshore low may briefly graze the coast with a
few showers mid-week. High pressure building in behind the cold
front will for the first half of next week will result in cool
nights and mild days. Low temps will probably be in the 40s to the
lower 50s with highs mainly in the 70-75 degree range. In fact...on
the coast and high terrain may see highs in the upper 60s at times.
This might occur near mid-week when a distant offshore low may
briefly graze the coast with a few showers. We may see a a brief
warm up on Thursday with perhaps highs approaching 80. However...a
cold front will likely bring the return to slightly cooler than
normal temps by Friday.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

     06z TAF Update...

Through 12z...High Confidence.

Mainly VFR conditions but some pockets of low clouds/fog patches may
flirt with areas near the south coast times. SW wind 6-12 knots.

Today...High confidence in trends, moderate confidence in timing.

VFR conditions in the morning will be followed by the development of
strong thunderstorms across interior southern New England after 16z.
Storms develop into a squall line and begin to weaken on approach to
the I-95 corridor. Brief IFR/LIFR conditions in heavy rain, cloud to
ground lightning and strong wind gusts are a concern for interior
southern New England. While winds will be stronger in thunderstorms
the gradient wind are SSW 10-15 knots with some gusts in the 25 to
30 knots are expected across much of the region by afternoon.

Tonight...High confidence in trends, moderate confidence in timing.

Severe thunderstorms diminish, rumbles of thunder possible overnight
for areas east of I-95. Here, ceilings fall to MVFR/IFR and -SHRA.
Areas northwest are low-end VFR through 06z/08z, then lower to MVFR
with pockets of IFR. SSW wind shifts to N behind the cold front, but
the Cape and Islands maintains a SSW flow overnight.

Sunday...High confidence in trends, moderate confidence in timing.

MVFR/IFR to start and slow improvements to VFR across western areas
of southern New England. The cold front is slow to exit, leading to
lower flight categories for much of the day across the I-95 corridor
where ceilings recover to a low-end VFR ceiling by mid afternoon.
With continued gradual clearing Sunday night into Monday morning.

KBOS Terminal...High confidence in trends, moderate confidence in
timing.

VFR into this afternoon with SW winds gusting between 25 and 30
knots. Possible -SHRA and -TSRA activity after 22z as a line of
storms moves from west to east but they will be weakening on
approach. Front becomes hung up overnight into Sunday morning with
lingering showers and MVFR ceilings.

KBDL Terminal...High confidence in trends, moderate confidence in
timing.

VFR until 18z/19z, after a line of strong to severe thunderstorms
will likely approach from the west. Front becomes hung up overnight
into Sunday morning with lingering showers and MVFR ceilings.

Outlook /Monday through Wednesday/...

Monday through Monday Night: VFR.

Tuesday: VFR. Breezy.

Tuesday Night through Wednesday: VFR. Breezy. Slight chance
SHRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

* A Small Craft Advisory: In effect through today for all waters.

Today and Sunday... High Confidence.

Gusty SSW wind today ahead of an approaching cold front, leading to
wind gusts of 25-30 knots, basis for today`s Small Craft Advisory.
Seas area increasing on the outer waters to 4-5 feet, near shore
waves are 2-4 feet. A strong cold front will move across the waters
late Saturday into Sunday morning, rain and thunderstorms are
possible.

Front does becomes stalled on Sunday over the eastern waters and
allows for continued showers and lower visibility. Seas subside for
the eastern waters, seas 2-4 feet, while seas remain elevated for
the southern waters 3-5 feet.

Outlook /Monday through Wednesday/...

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

Monday Night: Winds less than 25 kt.

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

Tuesday Night through Wednesday: Winds less than 25 kt. Areas
of seas approaching 5 ft. Chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 10 AM this morning to 8 PM EDT this
     evening for ANZ230-236.
     Small Craft Advisory until 8 PM EDT this evening for
     ANZ231>235-237-250-251-254>256.

&&

$$

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