491
FXUS61 KBOX 150509
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
109 AM EDT Tue Jul 15 2025

.SYNOPSIS...
Showers will diminish tonight. Heat and humidity will build once
again Tuesday through at least Thursday, along with chances of
showers or thunderstorms each afternoon and evening.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Key Messages:

 * Flood Watch canceled.
 * Warm and muggy night ahead tonight.

Showers and thunderstorms in western New England were weakening
with loss of daytime heating, but will persist for a little
longer as they feed off lingering instability located along PWAT
axis. As a result we have canceled the Flood Watch.

Otherwise, a warm and muggy night is in store with light S/SW
flow, which will also promote areas of low clouds and fog.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM WEDNESDAY/...
Key Messages:

 * Heat Advisory goes into effect for most of the region Tue.

Building ridge of high pressure brings the return of hot and humid
conditions Tuesday. Guidance has 925 temperatures increasing from
19C today to 24C tomorrow afternoon. At the surface, this translates
to high temperatures climbing into the upper 80s and low 90s for
most areas Tuesday afternoon. While these temperatures are far from
unheard of, dewpoint values will climb into the lower to mid 70`s
resulting in heat index values around 95 above. The greatest
likelihood of this will be for inland areas away from the Cape and
Islands.

Low temperatures will remain quite mild and dewpoints
high. Elevated low temperatures spell trouble for those without
access to proper sources of cooling and relief from the day`s
high temperatures.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Messages:

 * Hot and humid during the middle of this week, with elevated
   heat indices around 95-100F. Heat Advisories for Tuesday into
   Thursday for most of southern New England. Heat Advisory may
   be needed for Friday too.

 * Becoming more unsettled late Thursday-Friday with increasing
   chances for showers and thunderstorms.

Most of this portion of the forecast will see southern New England
om the warm and very humid side of a cold front. This front will
take its time to move from the Great Lakes and Saint Lawrence River
valley until it finally attempts to cross our region Friday night.
The holdup is a large high pressure off the southeast USA coast. The
position of this high pressure will keep pushing heat and humidity
our way.

Heat Advisories already posted for most of southern New England for
the middle part of this week. It may need to be extended into Friday
as well. Slightly cooler conditions anticipated once this front
passes by this weekend into early next week, but that should mean
right around average temperatures for this time of July.

The heat and humidity should mean at least a low risk for mainly
afternoon and evening thunderstorms. There remains 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 this
week. Friday is a more complicated forecast dependent upon the timing
of the aforementioned front.

Looking ahead to this weekend, this front doesn`t get too far south
of our region, and could return as a warm front sometime Sunday into
Monday. That could trigger another round of showers and possible
thunderstorms.

&&

.AVIATION /05Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

06z TAFs: Moderate confidence due to timing of low ceilings.

Few sprinkles crossing region overnight ahead of weak cold
front. Trend will be for MVFR/IFR ceilings to become more
widespread through sunrise, with IFR/LIFR ceilings expected near
South Coast, Cape Cod, and Islands. Should see improvement to
VFR 11z-15z but probably not until 17z-20z closer to Cape Cod
and Islands before LIFR returns there around sunset. VFR Wed.

S/SW winds 10kt or less through Wed, although sea breezes could
develop along E MA coast later this morning.

KBOS Terminal...Moderate confidence in TAF due to timing of MVFR
ceilings. Sea breeze could develop 15-16z but not yet confident
enough to include.

KBDL Terminal...Moderate confidence in TAF due to timing of IFR
ceilings.

Outlook /Wednesday Night through Saturday/...

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

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

Thursday Night: VFR. Breezy. Slight chance SHRA.

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

Friday Night: VFR. Slight chance SHRA.

Saturday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight through Tuesday...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. Inland Thunderstorms
are unlikely to affect the waters this evening. Winds turn more
SW on Tuesday between 10-15 knots.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt. Slight chance of rain
showers, slight chance of thunderstorms.

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of seas approaching 5 ft. Slight chance of rain
showers, slight chance of thunderstorms.

Thursday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft.

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

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

Saturday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for
     CTZ002>004.
MA...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for
     MAZ003>007-010>021-026.
RI...Heat Advisory from 11 AM this morning to 7 PM EDT Thursday for
     RIZ001>007.
MARINE...None.

&&

$$

SYNOPSIS...FT
NEAR TERM...JWD
SHORT TERM...FT
LONG TERM...Belk
AVIATION...JWD
MARINE...KP