126
FXUS61 KBOX 171907
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
307 PM EDT Thu Jul 17 2025

.SYNOPSIS...
Dangerous heat and humidity continues today. An approaching
cold front may bring hit or miss showers and thunderstorms
today, but much of the day will be dry. The cold front will also
bring an end to the heat and humidity later tonight with
beautiful dry weather Friday and Saturday. Another cold front
will likely bring a round of showers and embedded thunderstorms
to the region possibly late Saturday night, but more likely
Sunday, along with the return of some humidity. This will be
short-lived though as a dry and very pleasant airmass moves back
in time for the start of the next work week.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
Key Messages...

* Heat & Humidity continues this afternoon with Heat Indices 95-100

* Any Severe weather threat today should be isolated/localized

Details...

Today & Tonight...

A cold front is slowly making it`s way into southern New
England and bringing another risk for some scattered convection
late this afternoon and evening. Starting to see quite a bit of
mid-level dry air as well, so any severe storms that form will
likely be isolated in nature. Modest instability will quickly
develop with CAPE on the order of 1500 to 2500+ J/kg along with
25 to 30 knots of effective shear. A fair amount of 0-1 KM
helicity will also develop on the order of 100 to 200+ units.
Given the amount of dry air aloft, it`ll be a struggle for
storms to fire this far south; however, if some mesoscale
processes can come into play, there will be an
isolated/localized severe wind threat and brief torrential
rainfall.

Outside the convective threat...the majority of the day will
feature heat and humidity. High temps will be in the upper 80s
to lower 90s allowing heat indices to reach into the 95 to 100
degree range. Heat Advisories remain in place through 7 pm this
evening.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH FRIDAY NIGHT/...
Key Messages...

* Cold front brings relief from high heat and humidity

Details...

Friday...

Any showers that spring up this afternoon and evening will exit
southern New England overnight. A drier airmass moves in post-
FROPA, bringing much needed relief from the high heat and
humidity heading into the weekend. Mostly sunny & beautiful
weather for Fri with highs mainly between 80 and 85 and very
comfortable humidity levels.

&&

.LONG TERM /SATURDAY THROUGH THURSDAY/...
Key Messages...

* Another round of showers and thunderstorms late Sat night-Sun.

* Dry with average temps most of next week - warms up again Wed/Thu.

Northern stream dominates into next week which suppresses
subtropical ridge and keeps the heat/humidity away, though as we
head toward the end of next week there are signs the ridge may
return and bring increasing heat and humidity by Thu (although
probably not to the levels we saw this week).

Overall, dry weather should dominate with the exception of late
Sat night into Sun, when low pressure tracking to our NW brings
a round of showers/storms. ML guidance shows a low risk of
severe storms with environment featuring decent instability with
surface CAPE up to 2000 J/kg across interior and strong 0-6km
shear of 35-45kt, but as usual mid level lapse rates look fairly
weak. Moisture convergence looks impressive, however, with a
decent theta-e ridge over SNE and PWATs climbing to around 2",
so any storms could produce localized downpours and street
flooding, but not seeing much of a signal for flash flooding
right now (even in ML guidance).

&&

.AVIATION /19Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

18z TAF Update...

Today...Moderate confidence.

Mainly VFR, except MVFR for the South Coast & Cape terminals.
IFR across the Islands. Some light showers and possibly a rumble
of thunder over the Islands early this afternoon. Otherwise...
brief showers & t- storms possible across the region this
afternoon and early evening. The eastward extent of storm
activity is uncertain, with greatest chances for TSRA west of
ORH. SW winds may gust to between 20 and 25 knots by afternoon.

Tonight...High confidence.

Any isolated shower & t-storm activity should come to an end
this evening. Otherwise...VFR conditions as a dry NW flow of air
takes over later tonight into Friday. NW winds may gust between
20 and 25 knots behind the cold FROPA overnight into the first
half of Friday before diminishing.

Friday... High confidence.

VFR. Gusts diminishing mid-morning. Predominantly NNE winds,
though the Islands will likely turn SSE by Friday evening.

KBOS Terminal...Moderate confidence in TAF.

KBDL Terminal...Moderate confidence in TAF.

Outlook /Saturday through Tuesday/...

Saturday: VFR. Breezy.

Saturday Night: Mainly VFR, with areas MVFR possible. Breezy.
SHRA likely, chance TSRA.

Sunday: Mainly VFR, with local MVFR possible. Breezy. Slight
chance SHRA, slight chance TSRA.

Sunday Night through Monday Night: VFR.

Tuesday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Friday...High confidence.

Gusty southwest winds near 25 knots develop across our near
shore southern waters this afternoon given good mixing ahead of
an approaching cold front. We opted to issue a small craft
advisory for those near shore southern waters given it is peak
boating season. We also expect marginal SCA seas to develop with
long southerly fetch across the southern outer-waters by this
evening into Friday so we have headlines for that too.
Lastly...behind the cold expect a round of NW wind gusts of 25
knots overnight into Fri morning across our northern
waters...where we will have additional small craft headlines.

Outlook /Saturday through Tuesday/...

Saturday: Winds less than 25 kt.

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Seas locally approaching 5 ft. Chance of
rain showers, slight chance of thunderstorms.

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

Sunday Night through Tuesday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Heat Advisory until 7 PM EDT this evening for CTZ002>004.
MA...Heat Advisory until 7 PM EDT this evening for MAZ003>007-
     010>021-026.
RI...Heat Advisory until 7 PM EDT this evening for RIZ001>007.
MARINE...Small Craft Advisory from midnight tonight to 2 PM EDT Friday
     for ANZ230-250-251.
     Small Craft Advisory until 8 PM EDT this evening for
     ANZ231>237.
     Small Craft Advisory until 2 PM EDT Friday for ANZ254>256.

&&

$$

SYNOPSIS...McMinn/JWD
NEAR TERM...McMinn
SHORT TERM...McMinn
LONG TERM...JWD
AVIATION...McMinn/FT
MARINE...JWD