047
FXUS61 KBOX 131934
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
334 PM EDT Sun Jul 13 2025

.SYNOPSIS...
Mainly dry with seasonably warm and humid conditions continue
Sunday and most of Monday. A frontal system could bring showers
and thunderstorms on Monday evening. Increasing heat and
humidity around the middle of next week, which then looks to
break around Friday as a cold front brings yet another risk for
showers and thunderstorms.

&&

.NEAR TERM /THROUGH TONIGHT/...

Key Point

 * Seasonably warm and dry today

Stratus continued to gradually dissipate this morning. Expecting
it will be early afternoon before most areas can break out into
more sunshine. Minor tweaks to temperatures to bring them back
in line with observed trends.

Previous Discussion...

Very little change in airmass today as high pressure remains
offshore over the Gulf of Maine with a mid-level ridge over the
region. Low stratus and fog have once again spread across the
region as a result of the dewpoints in the 60s and light onshore
ESE flow. The fog should burn off between 7am-9am again today,
later across the Cape and Islands. After the low clouds and fog
burn off and lift, we should see mostly sunny skies once again
for the afternoon. High temperatures warm into the low to
mid-80s, with dewpoints still in the mid-to-upper 60s. Storm
remains well west of the SNE today as the axis of instability
moves further NW with the convergence boundary.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY NIGHT/...
Key Points

 * Seasonably weather again on Monday

 * Frontal system may bring heavy rain and localized flash
   flooding late Monday

Tonight:

Another rinse and repeat with low stratus and fog forming first
along the south coast and gradually lifting north through the
night with continued ESE onshore flow. Low temperatures remain
bound by the dewpoints again in the mid to upper 60s.

Monday:

A shortwave trough and weak frontal system exit the Great
Lakes and reach SNE late in the day. Before the frontal system
gets here, a rather similar day to Sunday with low clouds and
fog burning off by mid-morning, giving way to partly to mostly
sunny skies and highs in the low to mid-80s. MLCAPE values
should climb into the 500-1000 J/kg range across the interior in
the afternoon. Shear and mid-level lapse rate are still lacking
on Monday despite the weak shortwave moving through. With the
frontal system likely arriving in the evening, possibly even
after sunset, this should limit the severe wind threat. The
primary risk associated with thunderstorms will be heavy rain
and localized flash flooding. Weak shear means storms will be
slow-moving with little upscale growth. PWATS will increase to
around 1.8 inches on Monday, with warm cloud depths reaching as
high as 14,000 feet. Don`t think a flood watch will be needed at
this time due to uncertainty on the frontal timing and
convective placement, but future shifts may consider if
confidence begins to increase.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Key Messages:

* Hot and humid during the middle of next week, with elevated
  heat indices around 95-100F. Heat Advisories likely for at
  least Wed & Thur

* Becoming more unsettled late Thursday-Friday with increasing
  chances for showers/storms.

Tuesday-Thursday:

Heat and Humidity...

Weak mid-level ridging persists over the region Tuesday and
Wednesday with more zonal flow arriving Thursday. Temperatures aloft
increase with 850mb temperatures peaking at around 20C in the Weds-
Thurs timeframe. Ensemble guidance shows a plume of above normal
moisture in the flow which will add increased humidity to the mix.
Temperatures Tuesday through at least Thursday will range in the
upper 80s to mid 90s with the exception of the immediate coast. With
the the added element of higher humidity, it will feel more like mid
90s to near 100 Wednesday and Thursday. This combo provides a good
signal for potential heat impacts. NWS Heat Risk reflects this
potential well with Heat Risk in the Major Category Wednesday and
Thursday. It will be borderline Tuesday, with heat indices in the
low to mid 90s. There is a high probability that we will need Heat
Advisories for Wednesday and Thursday. We`ll need to keep an eye on
cloud cover for Thursday as this may limit highs a bit. Friday may
also end up being a hot day as well with ensembles showing little
change in the temperatures aloft with again a similar risk of clouds
limiting high temperatures.

Precipitation...

Tuesday and Wednesday stay mainly quiet when it comes to the passage
of any substantial system. Despite a weakly forced atmosphere, above
normal moisture, hot temps, and marginal daytime instability will
support isolated shower activity. Ensemble members are still spread
across the board with timing and given the low coverage nature of
the showers and lack of definitive forcing. This has made it it bit
more difficult to message in the forecast. Overall, expect a
tropical-like atmosphere with periods of higher cloud cover and
perhaps a spot shower.

There will be a better signal for more organized forcing later
Thursday and a weak trough shifts in from the west. This will bring
higher chances for more widespread showers/storms. Weak winds aloft
will support slower storm motions and given the high amounts of
moisture signal a threat for flash flooding. We`ll have to keep eyes
on that as we go through the week.

Friday-Weekend:

Ensemble guidance shows the main axis of the trough pushing across
the region by early Saturday. Similar story to Thursday with
increased chances for showers/storms later Friday ahead of an
approaching cold front. Winds aloft are slightly higher than
Thursday, but slower moving storms still look to bring a potential
threat for flash flooding. Friday may be another potentially hot
day. Ensemble members show more of a wider envelope of solutions for
temperatures Friday. However, there are still plenty of very warm
members that would support another Heat Advisory criteria given the
humidity. We`ll have to watch cloud cover as this could keep it cool
enough to not meet Advisory criteria.

Behind the trough, conditions dry out through the day on Saturday.
Ensembles hint at potential for another system later Sunday,
although confidence is low this far out.

&&

.AVIATION /20Z SUNDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

Today: Moderate confidence.

IFR/LIFR stratus and fog dissipating by 16z, then VFR
conditions for the rest of the day. South winds at 5-10 knots.

Tonight: High Confidence

IFR/LIFR CIGS build north again tonight with continued ESE flow.
stratus should have similar timing to last night.

Monday: Moderate Confidence

VFR after IFR CIGS burn off again. Chance for showers and
thunderstorms mainly across the interior

KBOS Terminal...Moderate confidence in TAF.

IFR CIGS lifting to M/VFR 14-15z similar to the last couple
days. VFR this afternoon. IFR stratus likely around the same
time tonight

KBDL Terminal...High confidence in TAF.

IFR CIGS lifting to M/VFR 12-13z similar to the last couple
days. VFR this afternoon. Less certain about low status again
for tonight.

Outlook /Tuesday through Friday/...

Tuesday: VFR. Slight chance SHRA, slight chance TSRA.

Tuesday Night through Wednesday: VFR.

Wednesday Night: VFR. Slight chance SHRA, slight chance TSRA.

Thursday through Thursday Night: VFR. Breezy. Slight chance
SHRA, slight chance TSRA.

Friday: Breezy. Chance SHRA, chance TSRA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Monday...High confidence.

Weak pressure gradient will keep winds/seas below Small Craft
Advisory thresholds through Sunday: seas 2-3 ft with E winds
over the southern waters and SE winds over the eastern waters up
to 15 kts during the afternoon hours, remaining light in the
overnight hours. Main concern for mariners will be areas of fog
tonight that may redevelop again tonight.

Outlook /Tuesday through Friday/...

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

Tuesday Night through Wednesday Night: Winds less than 25 kt.

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

Thursday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft. Slight chance of rain showers, slight chance
of thunderstorms.

Friday: Winds less than 25 kt. Seas locally approaching 5 ft.
Slight chance of rain showers, slight chance of thunderstorms.

&&

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

&&

$$

SYNOPSIS...Belk/Mensch
NEAR TERM...Belk
SHORT TERM...Belk
LONG TERM...Mensch
AVIATION...Belk/Mensch
MARINE...Belk/Mensch