231
FXUS61 KBOX 051857
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
257 PM EDT Thu Jun 5 2025

.SYNOPSIS...
A warm night with a chance for showers and storms across western
areas. Widespread showers and a few scattered severe storms, capable
of damaging winds on Friday. Potential exists for areas of flooding
where storms are able to train over the same area. Shower and storm
activity slowly winds down Friday night before yet more shower
chances arrive for Saturday as a cold front approaches from the
west. Showers may linger into Saturday with seasonable
temperatures making a return then through Monday. Dry conditions
expected Sunday heading into Monday before the next chance for
rain arrives Tuesday into Wednesday. Clearer conditions may make
a return heading into Thursday.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Key Messages...

* Anomalously warm night will create issues for those without proper
  access to cooling

* Scattered showers and an isolated storm or two approaches
  western MA before quickly dissipating

Tonight...

Convection will quickly weaken with the loss of daytime heating this
evening and overnight. The best chance for a shower or rumble of
thunder will be across portions of western Massachusetts. Otherwise,
it will be a dry but humid night as high pressure exits and we find
ourselves in its southwesterly return flow. Low temperatures will be
quite warm for this time of year, generally falling into the upper
60`s to near 70 in urban areas. A few widely scattered showers will
be possible around daybreak Friday but the bulk of the activity will
likely hold off until the afternoon.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Key Messages...

* Widespread showers and storms across the region Friday afternoon
  and evening with areas of torrential rain and possible flooding.

* Isolated to scattered severe storms could bring areas of damaging
  winds Fri afternoon

Details...

Friday...

Return flow around high pressure will maintain a warm moist airmass
over Southern New England on Friday. PWAT values of 1.5 - 2 inches
set the stage for what will likely be a heavy rain event across much
of the region Friday afternoon. The focus of precipitation will be a
convergent boundary that will likely set up across portions of
northern and central Massachusetts In terms of severe weather, while
shear values aren`t overly impressive (10-20kts) higher CAPE and
somewhat unusually steep mid-level rates should make for an active
afternoon and evening. HRRR and NAM soundings indicate the potential
for 1800-2500 J/kg of mixed-layer CAPE across a good portion of the
CWA by Friday afternoon. Additionally, forecast soundings show an
inverted-V signature with a pocket of drier air between 900 mb and
the surface. This drier layer, combined with weak shear and higher
PWATS would promote water-loaded updrafts that could quickly
collapse resulting in pockets of strong to damaging winds. CAMs show
activity starting as pulse-type storms earlier Friday afternoon
then congealing into small line/bowing segments later in the day.
Last but certainly not least, generally slow storm motion will
likely result in areas of flash/poor drainage flooding, especially
in areas where storms are able to train.

In summary, we expect a fair amount of showers and
thunderstorms to develop Friday. While the activity is possible
anywhere...the focus of the majority of them north of the
CT/RI/MA border. Main concern is pockets of torrential rainfall
with the stronger slow moving storms and very localized street
flooding. While shear is limited...20-30 knots north of the
CT/RI border combined with the UH swaths might be enough to
support an isolated severe weather threat. The main severe
threat would be localized strong to damaging wind gusts.

Friday Night...

Lingering shower and thunderstorm activity slowly winds down for
most of the region except for northwestern Massachusetts where there
will be a bit more forcing from a nearby cold front. Low
temperatures will be lower than Thursday night, generally falling
into the low to mid 60s regionwide.

&&

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

* Showers may linger into Saturday

* Dry Sunday and Monday before more rain is possible Tuesday

* Clearing Wednesday into Thursday with highs reaching the low to
  mid 80s

Details...

Showers may continue into Saturday as a cold front moves across
southern New England. Ensemble mean PWAT values are around the 1.5"
to 1.6" mark, so some localized downpours remain a possibility. Weak
lapse rates and limited CAPE should keep this as primarily showers,
but a rumble of thunder or two cannot be ruled out.

Following Saturday`s cold front, drier air fills in across the
region for Sunday into Monday. Winds shift to the NW Sunday morning
before shifting onshore Sunday afternoon and continuing through
Monday. This will lead to slightly cooler temperatures particularly
along the eastern coastlines compared to the rest of the region.
Highs at the start of the period through Monday will be the coolest
in this period before we return to the 80s for midweek. A low moving
to the northeast off the coast to our south may bring some scattered
showers to the Cape and Islands, but there`s also a good chance this
low misses completely and those areas remain dry. Southeast
flow makes a return for Tuesday, along with more rain chances.

A warm front is expected to move through Tuesday, placing the region
in the warm sector and elevating surface moisture again,
bringing more rain chances. With rain looking possible for most
of the day, highs may remain in the 70s. A cold front passes
through Tuesday night/Wednesday morning, shifting winds back to
the west and ushering in some drier air. Clearer conditions look
likely Wednesday heading into Thursday post-frontal passage.
Highs look to rebound into the 80s for midweek. Lows through the
extended period not expected to change much from night to
night, remaining mostly in the 50s and 60s across southern New
England.

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

18z TAF Update...

Today...High confidence.

VFR. SW winds 5-10 knots except for sea breeze development on
portions of the immediate coast and 15-20 knots gusts over the
Islands. There also will be an isolated shower/t-storm threat
this afternoon into this evening...but most locations will
remain dry.

Tonight...High confidence.

VFR outside some patchy of fog and low clouds which may develop near
the south coast, Cape and Islands. Winds becoming light-calm.

Friday...Moderate confidence.

Varying conditions expected with VFR conditions and then times of
MVFR-IFR cigs/vsbys in scattered showers and t-storms...a few of
which might be strong and contain torrential rainfall resulting in
brief LIFR conditions. Areal coverage will be greatest north of the
CT/RI/MA border. Light and variable winds.

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with areas MVFR possible. Chance SHRA,
slight chance TSRA.

Saturday Night: VFR. Slight chance SHRA.

Sunday: VFR.

Sunday Night: VFR. Chance SHRA.

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

Monday Night: Mainly VFR, with local IFR possible. Slight
chance SHRA.

Tuesday: Chance SHRA, slight chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Today through Friday...High Confidence.

Pressure gradient will remain weak enough to keep winds/seas below
small craft advisory thresholds through Fri. The main concern will
be the risk for an isolated t-storm this afternoon/evening near
shore with a better chance Fri especially across the waters adjacent
to northeast MA. Lastly...areas of fog will be possible late tonight
into Friday morning across the southern waters.

Outlook /Saturday through Tuesday/...

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

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers.

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

Sunday Night: Winds less than 25 kt. Slight chance of rain
showers.

Monday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers.

Monday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until 11 PM EDT this evening for CTZ002>004.
MA...Air Quality Alert until 11 PM EDT this evening for MAZ006-007-
     013-015-016.
RI...None.
MARINE...None.

&&

$$

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