488
FXUS61 KBOX 271122
AFDBOX
Area Forecast Discussion
National Weather Service Boston/Norton MA
722 AM EDT Sun Jul 27 2025
.SYNOPSIS...
A cluster of showers and a few embedded thunderstorms cross the
region on Sunday with the activity most widespread across western
and northern Massachusetts. Heat and humidity return Monday and
especially Tuesday when Heat Indices may approach 100 degrees in
some locations. Dry weather dominates much of next week outside the
risk for a few spot showers/thunderstorms. Much cooler/less humid
air follows behind a cold front late next week.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Key Messages:
* Showers and a few embedded thunderstorms expected today with
the greatest areal coverage north (northwest, north central
MA).
* Pockets of heavy rain possible with the highest chances in
northwest/northcentral MA.
Details:
A weak shortwave trough moves the the flow aloft today. This will
support a wave or two of showers and a few embedded thunderstorms
that move across the region today. For timing, HREF guidance shows
the most likely window for rain arriving between 6AM and 11AM
spreading from west to east. Coverage will be highest further north
(north of MA Pike), especially in northwest and north central MA
closer to the better synoptic forcing. Coverage will likely be less
going further southeast such as the Cape/Islands. The mean of high-
resolution guidance has the bulk of the precipitation exiting mid
afternoon with brief "clearing" or breaks in the clouds by the
evening for the most part. Some CAMs are showing the potential
for a secondary "wave" of isolated showers/storms later in the
afternoon from marginal elevated instability building in.
With plenty of moisture available (PWATs 1.5-2") and some marginal
instability, downpours with locally heavy rainfall are possible in
any embedded thunderstorms. Given increased cloud cover and shower
activity, temperatures will stay in the upper 70s to low 80s
today.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
Key Messages:
* Above normal temperatures and humidity return Monday for most
areas. Heat Advisory starts Monday.
Details:
Sunday Night:
Any lingering showers near the Cape/Islands should likely be exited
by Sunday evening. Conditions will briefly clear in the evening
timeframe. Wet ground and plentiful low level moisture, will
increase the potential for development of patchy fog tonight. Model
guidance is still struggling on coverage of the lower stratus/fog.
Based on a mean of the high res guidance, the main risk area for
this will be in southeast MA, RI, and the valleys of the interior,
but can`t rule out the low probability outcome of low clouds
getting into Boston as well tonight.
Monday:
A mid-level ridge pushes east into the region Monday which will
start the week off dry. 850mb temperatures warm back up to
around 18- 20C again trending temperatures back up from the
weekend. Highs will likely range in the upper 80s to low 90s for
the interior while the coastal areas will stay cooler in the mid
80s from sea breezes. Humidity will make it feel like 90-95F.
&&
.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Key Messages...
* Above normal temperatures/heat Tue/Wed. Heat Advisory Tuesday.
* Mostly dry this week with a chance of showers and t-storms Wed/Thu.
* Cooler for the second half of the week.
Details...
Ensemble guidance shows anomalous temperatures again for Tuesday and
potentially into Wednesday to some extent as a mid-level ridge
remains over the region. Tuesday will likely be the hottest day
of the week with highs in the low to mid 90s. Had to make some
small adjustments to dewpoints because they were a little too
high. Model soundings show sufficient mixing in the boundary
layer which would likely result in slightly lower dewpoints.
Regardless...it will still be humid with dewpoints around 70F.
This will make it feel more like upper 90s to near 100. A Heat
Advisory will be in effect for both Monday and Tuesday for much
of southern New England except the Cape/Islands and south coast.
Tuesday, a weak shortwave trough moves through the flow aloft which
will bring isolated to scattered showers and thunderstorms in the
afternoon. Ensemble guidance shows a more substantial wave moving
through in the Weds-Thurs timeframe. Still uncertainty in the
details such as timing, precipitation chances/amounts. What makes
this wave also more substantial aside from increased precipitation
chances will be the cooler airmass pushing in behind it. This will
break the above normal temperatures from earlier in the week.
Ensemble guidance shows good agreement with a transition to even
below normal temperatures with highs cooled into the mid 70s to low
80s by Friday.
&&
.AVIATION /12Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.
12z TAF Update...
Through 18z...Moderate confidence.
Showers begin to arrive from the west by 12z. MVFR and possible
isolated pockets of IFR develop behind shower activity from
west to east.
Sunday afternoon...Moderate confidence.
A cluster of showers and perhaps a few embedded t-storms works
across the region from west to east during the morning and
afternoon (11-21z). The areal coverage/intensity looks to be
greatest across northwest/north central MA with less as you move
southeast. Can`t rule out a few scattered showers or a storm
after 21z, mainly in west/central MA and CT terminals. VFR
conditions will be mixed with MVFR cigs/vsbys at times in
showers. S winds 5-10 knots.
Sunday night...Low confidence.
Forecast challenge will be ceilings. Ceilings may improve
temporarily to mainly VFR, but in that case may allow low
clouds and fog patches to develop. Areas with the greater risk
will be the Cape/Islands and coastal areas. Not confident enough
to fully message in TAF just yet, but hinted at potential with
FEW/SCT groups of IFR/LIFR conditions. Included FG in a PROB30
group for PVD and Cape/Islands terminals. Light SW winds
becoming NW after 06z.
Monday...High confidence in trends.
Any ceilings developed overnight will scatter out after 12z.
Winds light NW less than 10 kts with sea breezes developing by
the afternoon.
KBOS terminal...Moderate confidence in TAF.
Moderate confidence in timing of the showers this morning. Best
timeframe for seeing showers is 13z-18z, but can`t rule out an
isolated shower just outside that timeframe. Low chance (< 20%)
for an isolated shower/storm after 20z. Ceilings may be tricky
this evening with some model guidance hinting at low ceilings
sneaking into the terminal after 00z. Not confident enough to
include in the TAF yet, but have hinted at it with SCT lower
ceilings.
KBDL terminal...Moderate confidence in TAF.
Moderate confidence with timing of showers as they arrive from
west early this morning. The AM wave of showers should be out by
16z, with perhaps a stray shower or two around. There is a
chance for an isolated shower/storm after 20z at/near the
terminal. Probability (<30%) given isolated nature.
Outlook /Monday Night through Thursday/...
Monday Night through Tuesday Night: VFR.
Wednesday: VFR. Slight chance SHRA, slight chance TSRA.
Wednesday Night through Thursday: VFR. Chance SHRA, slight
chance TSRA.
&&
.MARINE...
Forecaster Confidence Levels...
Low - less than 30 percent.
Medium - 30 to 60 percent.
High - greater than 60 percent.
Through Monday...High confidence.
SSW winds 10-20 kts today. We will have to watch for areas of
fog to develop across the southern waters tonight. Winds
decrease into early Monday less than 15 kts.
Outlook /Monday Night through Thursday/...
Monday Night through Wednesday: Winds less than 25 kt.
Wednesday Night through Thursday: Winds less than 25 kt. Chance
of rain showers, slight chance of thunderstorms.
&&
.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 11 AM Monday to 8 PM EDT Tuesday for
CTZ002>004.
MA...Heat Advisory from 11 AM Monday to 8 PM EDT Tuesday for
MAZ003>007-010>019-026.
RI...Heat Advisory from 11 AM Monday to 8 PM EDT Tuesday for
RIZ001>004.
MARINE...None.
&&
$$
SYNOPSIS...Mensch
NEAR TERM...Mensch
SHORT TERM...Mensch
LONG TERM...Mensch
AVIATION...FT
MARINE...Mensch