431
FXUS61 KBOX 131442
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1042 AM 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 /MONDAY/...
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 /MONDAY NIGHT THROUGH SATURDAY/...
Key Messages:

* Very warm to hot during the middle of next week, with elevated
  heat indices around 95-100F. Heat headlines possible.

* Becoming more unsettled late Thursday-Friday with increasing
  chances for showers/storms, especially Friday with a cold
  front.

Details:

Tuesday-Thursday:

Tuesday through Friday, a mid-level ridge builds over the
regions. Temperatures aloft increase with 850mb temperatures
peaking at around 20C in the Weds-Thurs timeframe. A good amount
of moisture gets transported over the ridge by Wednesday adding
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 to near 100
Wednesday and Thursday.

Overall, there are no major disturbances embedded in the flow
during that timeframe which will reduce the threat for
widespread showers/thunderstorms. Ensemble members display
potential for a few showers. Members are still spread across
the board with timing and given the low coverage nature has been
difficult to message in the forecast. Until better agreement on
timing, no major adjustment have been made to the forecast.
There will be a better signal for forcing later Thursday with
corresponding increased chances for showers and thunderstorms.

Thursday - Friday:

A mid-level trough approaches the region, Thursday into Friday.
This will shift the pattern to becoming more unsettled with
increasing potential precipitation starting later Thursday.
Ensemble members are still across the board when it comes the
the precipitation chances and the timing leading to lower
confidence this far out. A front will eventually push through on
Friday with the main trough axis. This should bring the highest
chances of seeing precipitation.

&&

.AVIATION /15Z SUNDAY THROUGH THURSDAY/...
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 /Monday Night through Thursday/...

Monday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA, slight chance TSRA.

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

Tuesday Night: VFR.

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

Thursday: VFR. 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 /Monday Night through Thursday/...

Monday Night through Wednesday: Winds less than 25 kt.

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

Thursday: Winds less than 25 kt. Areas of seas 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...Mensch/KP
NEAR TERM...Belk/KP
SHORT TERM...KP
LONG TERM...Mensch
AVIATION...McMinn/KP
MARINE...KP