594
FXUS61 KBOX 181758
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
158 PM EDT Tue Aug 18 2026

.WHAT HAS CHANGED...
Small lowering of shower/thunderstorm chances for Thursday.

&&

.KEY MESSAGES...

- Rip current risk continues along the east coastal areas into
  this evening.
- Small chance of a shower or thunderstorm through this evening
  across the interior, otherwise tranquil weather through
  Wednesday night.
- Unsettled weather returns Thursday with high pressure and
  pleasant weather following for Friday
- Another round of unsettled weather possible for the second
  half of the weekend.


&&

.DISCUSSION...
KEY MESSAGE 1...Rip current risk continues along the east coastal
areas into this evening.

Swell energy coming in from the east has been resulting in rip
currents along primarily east facing beaches today. This energy
will slowly be diminishing this evening and overnight. As that
happens, the risk for rip currents along primarily east facing
beaches will also slowly diminish.


KEY MESSAGE 2...Small chance of a shower or thunderstorm through
this evening across the interior, otherwise tranquil weather
through Wednesday night.

Although it`s taken awhile, much of the low clouds across the
eastern half of southern New England have finally started to
lift and break up. Satellite imagery shows daytime cumulus
developing across the interior thanks to relatively abundant low
level moisture. However the latest mesoanalysis does not show
much mixed layer CAPE and still some CIN due to a weak inversion
aloft. Although a shower or isolated brief thundershower is
possible, the chances are pretty low. Did maintain continuity
with previous forecasts and painted in a roughly 20% chance,
mainly across the Worcester Hills into NE CT and northern RI.
This is where the thermal gradient (due to slightly cooler
temperatures where the low clouds hung around longest and where
more sunshine has developed) will also be maximized. Otherwise,
the next 36 hours will be dry for the vast majority of the
region. Could be another round of low clouds and some fog across
southeast MA/Cape/Islands late tonight due to the still somewhat
humid airmass. Otherwise models are all consistent with dry
weather tomorrow. With plenty of sun and 925mb temperatures
around 20C, we should see surface temperatures either side of
30C (ie: mid 80s F). Stuck with model blend for that reason.
Quiet and seasonable conditions continue Wednesday night.


KEY MESSAGE 3...Unsettled weather returns Thursday with high
pressure and pleasant weather following for Friday

Guidance continues to show a shortwave moving east towards the CWA
on zonal flow Thursday. Aloft, the jet stream becomes cyclonically
curved placing our region under the jet`s left exit region. These
mid and upper level dynamics provide ample forcing for
precipitation. The caveat here will be dry low and mid level
moisture profiles across much of the region. Thus, expecting mainly
light showers across the southern portion of the CWA with mostly
cloudy skies elsewhere. Still, there are some discrepancies within
guidance suites. Namely, the global models, including the NBM, show
a drier solution with probs of QPF exceeding 0.25" less than 30%. In
contrast, CAMs show a more amplified, moisture-rich wave with
locally heavy rain and a low risk for thunderstorms. Think the
solution lies somewhere in between the two extremes with scattered
showers possible mainly along and S of the Mass Pike Thursday
afternoon and evening.

The frontal wave passes E of the region late Thursday. Dew point
temperatures crash into the upper 50s Friday as high pressure builds
overhead. Temperatures will likely be in the low 80s and down to the
mid 70s, particularly along the coasts where onshore winds will keep
it slightly cooler.


KEY MESSAGE 4...Another round of unsettled weather possible for
the second half of the weekend.

Guidance shows an even larger shortwave arriving from the Great
Lakes later Saturday with plenty of upper-level energy. Behind the
lead shortwave, a series of shortwaves moving along the boundary
that may stall just off the east coast could bring chances for
showers. Thunderstorms could be a possibility depending on if these
waves could take advantage of daytime heat. More details will become
apparent as we approach this timeframe. At the moment, guidance
blends show a 30-50% chance of rain through much of the interior and
60-70% along the coast from Saturday night to Monday morning.



&&

.AVIATION /18Z TUESDAY THROUGH SUNDAY/...
Forecaster Confidence Levels...

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

18z TAF Update...moderate confidence

Trending toward VFR in most areas. Could see an isolated SHRA or
even -TSRA across parts of the interior through 23z. Felt
chances were only barely high enough to include PROB30 at ORH
and PVD. Most difficult aspect of the forecast is the risk for
another round of low clouds and fog overnight. Guidance has
backed away from previous depictions of widespread IFR/LIFR, so
the TAFs were also trended that way. Any low clouds/fog that
does form should be gone 12-14z tomorrow. Otherwise light
surface winds that will slowly transition to southwesterly late
tonight and Wednesday morning. Otherwise VFR expected tomorrow
and tomorrow night. Could be an east coast sea breeze tomorrow
afternoon.


KBOS Terminal...Moderate confidence in TAF. Expect MVFR
conditions to develop late tonight. Perhaps ceilings becoming
IFR.

KBDL Terminal...Moderate confidence in TAF. There is a very
small (10%) chance for -SHRA this afternoon, but not enough to
include in TAF.

Outlook /Thursday through Sunday/...

Thursday: VFR. Slight chance SHRA.

Thursday Night through Friday Night: VFR.

Saturday: VFR. Chance SHRA.

Saturday Night: Mainly VFR, with local IFR possible. Chance
SHRA.

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

&&

.MARINE...
Forecaster Confidence Levels...

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

Through Thursday...High confidence.

Generally light winds into Thursday with only weak pressure
patterns. Seas will continue to diminish as the swell energy
slowly diminishes.

Outlook /Thursday through Sunday/...

Thursday: Winds less than 25 kt.

Thursday Night through Friday Night: Winds less than 25 kt.
Chance of rain showers.

Saturday through Saturday Night: Winds less than 25 kt. Rain
showers likely, slight chance of thunderstorms.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...High Risk for Rip Currents until 8 PM EDT this evening for MAZ007-
     015-016-019-022-024.
RI...None.
MARINE...None.

&&

$$

DISCUSSION...FT/Nash
AVIATION...FT/Nash
MARINE...FT/Nash