446
FXUS61 KBOX 131933
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
333 PM EDT Thu Aug 13 2026

.WHAT HAS CHANGED...
Showers and storms remain possible this afternoon, diminishing into
tonight. Some have overachieved and indicated severe features,
which will continue to be monitored.

&&

.KEY MESSAGES...

- Scattered showers and thunderstorms continue this afternoon
  and will be possible again tomorrow afternoon.

- Dry and pleasant weekend in store for the region.

- Rain, possibly heavy at times, Sunday night into Monday
  morning.

&&

.DISCUSSION...
KEY MESSAGE 1...Spotty showers and thunderstorms continue this
afternoon and will be possible again tomorrow afternoon.

Spotty showers and thunderstorms have popped up this afternoon in SE
MA and along the south shore as a surface front pushes through the
region. Interactions with the sea breeze boundary have also
ramped these up, some turning severe. Showers and storms have
also popped up just NW of MA, moving SE which may end up
impacting interior MA. Winds have already shifted more NW in
areas behind the front. These showers and storms will continue
to pop up through the rest of the afternoon but will diminish
heading into tonight. A thunderstorm risk exists for tomorrow as
well, though the risk of them turning severe is low and limited
based on the latest CAMs.

Following the front, drier air will be ushered into the region. This
will bring PWATs closer to an inch, diminishing further following
Friday`s cold front. HREF guidance has values falling to as low as
around 0.5". The chance for isolated showers and storms returns in
the afternoon tomorrow, though  Temperatures will remain seasonable
with highs in the 80s. Lows tonight will dip into the mid 50s, then
cooler tomorrow night with a greater possibility for radiational
cooling. Urban areas will remain slightly warmer.

KEY MESSAGE 2...Dry and pleasant weekend in store for the region.

Sprawling continental high pressure builds S from Canada this
weekend leading to mild and pleasant days and cool nights.
Airmass will be quite dry with column-average PWATs falling to
0.4-0.5 inches. This fall-like airmass will be a welcome break
from our recent stretch of humidity where dew point temperatures
have been in the upper 60s to low 70s for the past several
weeks. It will be a mild stretch with the early August sun
bringing temperatures near or slightly below seasonable levels,
ranging from the upper 70s to lower 80s. Saturday night into
Sunday morning, clear skies and light winds provide favorable
conditions for effective radiational cooling. Lows Saturday
night range from the low to mid 50s for the majority of the CWA
and near 60 closer to urban centers. Some guidance even suggests
low in the upper 40s across portions of Northern Massachusetts.

High pressure moves offshore early Sunday, allowing for an
increasing SWrly return flow. The SW winds bring the return of 60s
dewpoints though temperatures remain comfortable with highs in the
upper 70s. Clouds will be on the increase as a shortwave and
associated frontal system approach from the west later Sunday
afternoon into the evening. Guidance shows a low level jet
developing and bringing elevated PWATs over the region after dark
Sunday. More details about this rainfall threat in the next key
message.


KEY MESSAGE 3...Rain, possibly heavy at times, Sunday night into
Monday morning.

The next opportunity for rainfall comes during the second half of
Sunday into Monday. However, there remains uncertainty regarding
rainfall amounts, as the best forcing is associated with the surface
low and track variability makes it difficult to pin down where the
greatest rainfall will occur. This is worth monitoring, as global
guidance is in agreement that PWATs may exceed 2 inches, indicating
the potential for heavy rainfall. This is also supported by a
Marginal Risk (level 1 of 4) for excessive rainfall. Global
ensembles highlight areas north of I-90 as having the greatest
likelihood for measurable rainfall, with a 40-60 percent probability
of at least a half inch of rain between Sunday evening and Monday
evening. That said, if rainfall becomes more convective, localized
totals could be higher. One positive is that this system appears
progressive, with the cold front clearing east of New England on
Monday. Drier air then advects in from the northwest, leading to
another dry stretch from the latter half of Monday through Tuesday
and Wednesday as surface high pressure builds back into the region.
During this time, temperatures are expected to remain seasonable,
with highs in the lower to middle 80s and tolerable humidity as dew
points remain in the lower 60s.

&&

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

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

Rest of Today...Moderate confidence.

Chance for SHRA/TS remains through this afternoon, and we have
even seen one storm over the south shore pop up. CU out across
much of E to SE MA is quite agitated, so this will continue to
be monitored through the day. Spotty coverage continues to be
the expectation. Winds have started shifting more WNW/NW and
will continue to do so from W to E as the afternoon goes on and
the front moves through. Winds should generally remain around
or below 10 kt.

Tonight...High confidence.

Any lingering SHRA dissipates early, with VFR conditions prevailing
thereafter. Low probability of some patchy fog in the
CT Valley a little before sunrise. NW winds 5-10 kt.

Friday...High confidence.

VFR. Low probability of an isolated afternoon thunderstorm across
interior southern New England, so not included in TAFs at this
time; otherwise, dry. NW winds 8-12 kt.

Friday Night...High confidence.

VFR. Light NW to N winds that may go calm in some areas,
particularly in the interior. Given the drier conditions,
probability for fog in the usual areas is low at this time.

KBOS Terminal...High confidence.

KBDL Terminal...High confidence.

Outlook /Saturday through Tuesday/...

Saturday through Saturday Night: VFR.

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

Sunday Night: MVFR/IFR conditions possible. Breezy. SHRA,
chance TSRA.

Monday: VFR. Breezy. Chance SHRA, slight chance TSRA.

Monday Night through Tuesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Friday Night...High confidence.

Isolated showers and thunderstorms will remain possible over the
waters, particularly around the Cape and south shore. Winds
continue shifting NW as the front moves over the waters through
this evening, sustained at 10-15 kt. This will continue through
Friday as well. Winds shift more N Friday night. Outside of any
spotty afternoon showers and storms, conditions will remain dry.

Outlook /Saturday through Tuesday/...

Saturday through Saturday Night: Winds less than 25 kt.

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

Sunday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Local rough seas. Rain showers likely,
slight chance of thunderstorms.

Monday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas. 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.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...Hrencecin/FT
AVIATION...BW/Hrencecin/FT
MARINE...Hrencecin/FT