999
FXUS61 KBOX 202318
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
618 PM EST Thu Nov 20 2025

.SYNOPSIS...
High pressure overhead tonight shifts east of the region on Friday.
A weak wave of low pressure passes well to our south Friday
night into early Saturday...perhaps bringing a few showers
mainly for areas near the south coast. Otherwise...dry/seasonable
weather is on tap for the weekend into Monday. Low pressure
approaching from the west will likely bring a period of rain
later Tuesday and/or Wednesday. Dry weather should return in
time for Thanksgiving.

&&

.NEAR TERM /THROUGH FRIDAY/...
Key Messages...

* Dry but chilly again tonight with lows mainly in the 20s

Details...

Tonight...

A ridge of high pressure over southern New England will result in
another dry & chilly night with calm/light winds. This should allow
for excellent radiational cooling conditions with low temps
bottoming out mainly in the 20s. A few of the normally coldest
spots will probably bottom out near 20! Meanwhile...the urban
heat island of Boston will be the mild spot with lows only
dropping into the lower to middle 30s.

As the prior forecast mentioned...slightly higher dewpoints
across eastern MA may allow some fog patches in the typically
prone low-lying locations overnight. There is a low risk that
this could lead to patches of black ice with the best chance
towards the Cape/Islands. Not too confident on this happening
because true warm advection at the surface does not occur until
after 12z and the airmass is fairly dry. Certainly something to
keep a close eye on overnight.

&&

.SHORT TERM /FRIDAY NIGHT/...
Key Messages...

* Partly sunny Fri...Highs mainly in the upper 40s to lower 50s
* A few showers possible later Fri night, mainly near the south coast

Details...

Friday...

The ridge of high pressure shifts to our southeast Friday. A mixture
of clouds and sun expected with the clouds more favorable later in
the day. The departing high will allow a return southwest flow
of air to develop at the surface. Mid-level temps warm a bit
too...so thinking highs will be a few degrees milder than today.
High temps should mainly be in the upper 40s to the lower 50s
except lower-middle 40s in the higher terrain.

Friday night...

A weak wave of low pressure will be moving east across the mid-
Atlantic states Friday night. Strong 500 mb low across Quebec
will tend to suppress this system to our south. In fact...the
latest model guidance continues to trend further south with the
main rain shield. GFS still the outlier bringing a period of
widespread rain to most areas later Friday night/early
Saturday...but the rest of the guidance keeps most of the rain
near the south coast. Still time to sort out...but thinking much
of our region may see little or no rainfall. Low temps should
bottom out in the 30s to the lower 40s and we may see some fog
patches.

&&

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

* Chance for light rain showers Friday night into Saturday morning
  across the South Coast.

* Mostly dry and sunny through the weekend, but returning to
  unsettled conditions by mid-week.

Continue to expect Friday to remain dry during the daytime hours
with a cold front pushing through New England Friday night into
Saturday. Latest guidance is trending towards a later arrival as
well as keeping showers south of the Mass Pike and along the South
Coast. NBM probs for greater than 0.25"/24 hours remains greatest
along and south of the I-95 corridor, and probs of 0.5"/24 hours the
greatest (only 25-30 percent) over the Islands. GFS continues to
remain the most robust of the models, but thinking it may be an
outlier at this point.

Mostly dry and sunny for the remainder of the weekend, with
afternoon high temperatures in the mid to upper 40s  (except mid to
upper 30s for higher terrain areas).

Next chance for rain showers comes mid-week as another low pressure
system passes through the James Bay and a high pressure moves
offshore. Still quite a bit of uncertainty given how far out we are,
but something we will continue to watch as Thanksgiving
approaches.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

00z TAF Update...

This afternoon through tonight...High confidence.

VFR for most, however, and MVFR cloud deck will remain over SE
portions of MA through about 06z tonight. After 06z, localized
areas of MVFR/IFR ground fog could develop. Winds remain light
and variable.

Friday...High confidence.

VFR with periods of MVFR. Increasing SW winds at 10-15 knots

Friday night...Moderate confidence.

Lowering CIGS overnight to low end MVFR to IFR. Rain stays
confined to the south coast. Winds turn NW late overnight.

KBOS Terminal...High confidence in TAF.

VFR with periods of MVFR possible this evening and again
tomorrow afternoon. Winds turn SW overnight and increase to
10-20 knots

KBDL Terminal...High confidence in TAF.

VFR turning MVFR tomorrow. Winds turn SW tomorrow at 10-15
knots.

VFR becoming MVFR tomorrow.

Outlook /Saturday through Tuesday/...

Saturday: Mainly VFR, with local MVFR possible. Breezy.

Saturday Night: VFR. Breezy.

Sunday through Monday: VFR.

&&

.MARINE...
Forecaster Confidence Levels...

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

Tonight through Friday night...High confidence.

High pressure across the waters tonight will shift to their east Fri
into Fri night. A weak wave of low pressure then will pass to our
south Fri night. This all will result in a continued weak
pressure gradient keeping winds/seas below small craft advisory
thresholds through Friday night.

Outlook /Saturday through Tuesday/...

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of rain showers, patchy fog.

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain.

Saturday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.

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

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

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

&&

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

&&

$$

SYNOPSIS...Frank/McMinn
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...McMinn
AVIATION...KP
MARINE...Frank/McMinn