221
FXUS61 KBOX 180725
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
325 AM EDT Sat Jul 18 2026

.WHAT HAS CHANGED...
Rip Current Statement was issued for Sunday. Monitoring for
possible heavy rain and severe weather this afternoon south of
the Mass Pike, and again tonight in interior MA/CT.

&&

.KEY MESSAGES...

- Showers and scattered thunderstorms with torrential rainfall
  along with a localized flash flood threat Sat afternoon and night.
  A few severe thunderstorms possible too with the greatest risk
  interior MA/CT and onto the south coast. Areas of smoke return
  late tonight into Sat but not as bad as what we had Wed.

- Drying out Sunday into the start of next week, but more
  active weather returns around midweek.

&&

.DISCUSSION...
KEY MESSAGE 1...Areas of smoke re-developing this morning. Then two
periods of storms today/tonight: one mainly south of the Mass Pike
early to midafternoon, late in the day into tonight in the interior.
Torrential downpours are possible, and a lesser risk for severe
weather could also occur.

Active Saturday in store as a seasonably-strong frontal system moves
through Southern New England over the next 24 hours. First, on
the returning smoke. Tough to remotely sense via satellite
imagery with the cloud cover around, but based on AQI readings
early this morning, the northern edge of the plume of near-
ground smoke trails from western NY southward into central NJ.
Smoke progs show this returning northward into southern New
England by early to mid this morning. While the morning to early
afternoon end up dry, expect skies to turn hazy again with
increasing SWly winds. Air Quality Alerts remain in effect for
today for PM2.5, at request of our state environmental agency
partners.

Now for the shower and thunderstorm threats today/tonight. The
frontal system expected to affect our area has with it pretty
impressive wind fields for mid-July, which will support some severe
weather potential, but will also make the storms fast-moving, which
could help limit flash flooding. I`m a little skeptical on the
instability ingredient though, as the smoke conditions and potential
for poor recovery/limited breaks in the clouds could limit how
strong storms get.

The first round of showers and thunderstorms moves in around early
to mid-afternoon (1-3 PM) associated with a strong warm front, which
will bring mid-70s dewpoints and PWAT values in the 2 to 2.25" range
to Southern New England, with weakening stability profiles. Most of
the CAMs pencil in areas south of the Mass Pike as having the most
concentrated area of showers and storms, and especially the Hartford-
Providence-Southeast MA corridor. Opted for high Likely to
Categorical PoP for these areas, then just a generic Chance PoP
north of here to make the distinction. The main risk with this first
wave of storms is the risk for torrential downpours capable of
street flooding. Continued QPF placement uncertainties
precluded a Flood Watch with this issuance, as there are still a
good number of guidance sources which shift the rain/storms
into the southern waters. I still added heavy rain wording to
the grids for these areas to convey that message in lieu of the
Watch, and the potential for high rain rates in urbanized areas
could still trigger a need for flash flood warnings this
afternoon if and where any cell training occurs. There is a low
risk for localized straight line wind damage or a brief tornado
due to the low level windfields (300 units of 0-1 km SRH is
notable), but the severe weather risk looks secondary to the
heavy rain potential.

As this initial round of showers/storms shifts southward, the next
period of showers and thunderstorms arrives late in the day into
tonight (between 6 to 11 PM) with the cold front. Most models show a
pretty extensive line of thunderstorms developing late this
afternoon as the front moves southward across upstate NY and VT.
We`ll have to watch the northeast extent of this line as it slips
south-southeast into the Berkshires, northern CT and central MA,
with less of a risk into eastern MA. Straight-line wind damage,
frequent lightning and torrential downpours would be the main risks
with this second round. The risk for late-evening strong storms is
more uncertain the further south one goes, since these areas will
probably have been worked over pretty well with the afternoon heavy
downpours/storms, with weakening trends more likely. Front clears
into the southern waters overnight, with northwesterly breezes and
turning much less humid by sunrise.

KEY MESSAGE 2...Turning drier and seasonable Sunday and Monday, but
Sunday will feature a high risk for rip currents on south-facing
beaches.

The cold front brings a stretch of pleasant summer weather Sunday
and Monday, with low humidities and temperatures in the 70s to mid
80s, to go along with NW breezes Sunday. At the beaches though,
swell directions Sunday are still oriented from SW to NE from
today`s storm system, with seas in the 4 to 6 ft range. This
will favor a high risk for dangerous rip currents. With Sunday
being a better day to go to the beach than today, issued a rip
current statement for the southern beaches.

KEY MESSAGE 3...Active weather returns midweek with showers and
thunderstorms.

Although there`s the usual uncertainty in the details at this time
horizon, most of the global ensembles show another potent northern
stream upper trough interacting with a tropical Gulf moisture feed,
with a risk for showers and thunderstorms Tuesday and possibly into
Wednesday too. Temps warm to above average levels and we turn quite
a bit humid too, so the risk for downpours is in the cards as we
move into midweek.

&&

.AVIATION /06Z 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 Tonight: Moderate confidence.

VFR through 16z today, although VFR-visby FU returns early
today from the south. SW winds increase to 10-15 kt with gusts
25-30 kt. After 16z, categories then drop to MVFR levels with
two periods of storms. First takes place 17-23z mainly BDL- PVD-
Cape airports, with IFR-visby heavy SHRA/VCTS. Lesser risk
north. Next round of storms occurs mainly ORH to BDL, perhaps to
BOS with cold front between 22-03z, with PROB30s given
uncertainty on how strong storms may get. Later TAF issuances
will need to reassess the 2nd period of storms. Improvement to
VFR from 02-06z NW to SE, with windshift to NW around 10-12 kt
into Sunday pre-dawn.

Sunday: High confidence.

VFR. NW winds around 10-15 kt.

KBOS Terminal...Moderate confidence in TAF. 6SM/P6SM FU this
morning. First round of showers/storms 18-22z stays mainly
south of terminal (VCSH) with MVFR cigs, then a drier break
before risk for TS after 01z (PROB30). SW winds gusting upper
20s kt range.

KBDL Terminal...Moderate confidence in TAF. 6SM/P6SM FU this
morning. MVFR-IFR after 17z with initial +SHRA/VCTS, then a
break before a line of strong TSRA nears terminal after 23z
(PROB30). SW winds gusting mid 20s kt range.

Outlook /Sunday Night through Wednesday/...

Sunday Night through Monday Night: VFR.

Tuesday: VFR. Breezy. Chance SHRA, chance TSRA.

Tuesday Night: Mainly VFR, with areas MVFR possible. Windy with
areas of gusts up to 30 kt. SHRA, slight chance TSRA.

Wednesday: Mainly VFR, with areas MVFR possible. Windy with
gusts up to 35 kt. SHRA likely, chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Tonight: High confidence.

SCAs continue in effect for today and into parts of Sunday as
well. Southwest wind gusts 25-30 knots are expected today with
seas becoming rough, increasing to 6-8 ft offshore. Seas will
also respond and become quite rough across the waters. Scattered
thunderstorms later Sat and Sat night may produce localized
stronger wind gusts as well...which may require the issuance of
some special marine warnings.

Sunday: High confidence.

NW winds around 15-20 kt, with seas around 4-6 ft. High risk for
rip currents at the beaches/surf zone.

Outlook /Sunday Night through Wednesday/...

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

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

Monday Night: Winds less than 25 kt.

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Chance of rain showers, slight chance of
thunderstorms.

Tuesday Night: Low risk for gale force winds with gusts up to
35 kt. Areas of rough seas. Rain showers, chance of
thunderstorms.

Wednesday: Moderate risk for gale force winds with gusts up to
35 kt. Rough seas up to 16 ft. Rain showers likely, slight
chance of thunderstorms.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Air Quality Alert until midnight EDT tonight for CTZ002>004.
MA...Air Quality Alert until midnight EDT tonight for MAZ002>024-
     026.
     High Risk for Rip Currents from Sunday morning through Sunday
     evening for MAZ020-022>024.
RI...High Risk for Rip Currents from Sunday morning through Sunday
     evening for RIZ006>008.
     Air Quality Alert until 11 PM EDT this evening for RIZ001>008.
MARINE...Small Craft Advisory from 11 AM this morning to noon EDT
     Sunday for ANZ230>237-250-251.
     Small Craft Advisory from 11 AM this morning to 8 PM EDT
     Sunday for ANZ254>256.

&&

$$

DISCUSSION...Loconto
AVIATION...Loconto
MARINE...Loconto