831
FXUS61 KBOX 210737
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
237 AM EST Fri Nov 21 2025

.SYNOPSIS...
High pressure overhead shifts east of the region 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 and seasonably cool weather is on tap
for the weekend into Monday. Low pressure approaching from the west
could bring a period of rain later Tuesday and/or Wednesday. With
uncertainty on how quickly dry weather arrives for Thanksgiving.

&&

.NEAR TERM /THROUGH TODAY/...
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.

High pressure drops south, allowing winds to flip southwest and weak
WAA advection to kick in.  WAA will bring increasing clouds by mid
to late morning. Even without the sunshine we have had the last few
days, highs will still be able to jump into the upper 40s to low 50s
with the WAA.  Pressure gradient tightens a bit tomorrow, with winds
around 10-15mph in the afternoon.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM SATURDAY/...
A weak wave of low pressure once again passes to the south of SNE as
upper-level southern stream energy fails to connect with the
northern stream shortwave. Guidance continues to trend precipitation
further south, with most of the Hi-res guidance sources keeping
light rain confined to the South Coast and Islands.  Global guidance
is a bit more mixed, with the GFS still trying to bring the low
further north, while EURO and Canadian pitch a near shutout for the
region. Temperatures on Saturday morning wont be quite as chilly as
we`ve been used to, as cloud cover should hold temps in the mid to
upper 30s.  Low pressure moves offshore with rain ending by noon.  A
cold front helps clear the clouds for Saturday afternoon, but
temperatures begin falling from the upper 40s to the mid-30s by
sunset.

&&

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

* Generally quiet and cool conditions to end the weekend into early
  next week, followed by a warming trend and a return to unsettled
  conditions by mid next week.

Overview: Surface high pressure builds across the east coast for the
end of the weekend through early to middle of next week. During this
time period the mid-levels are nearly quasi-zonal with uneventful
day-to-day weather conditions. A shift in the mid-levels occurs the
second half of Tuesday into Wednesday, with ridging in the west and
troughing in the east. On Tuesday, ensembles are developing a system
albeit a fair amount of spread in the guidance across the northern
tier of the Great Lakes with a secondary low across southern half of
New England. LREF cluster analysis is split nearly 50/50 on day 6
which are Wednesday into Thursday. Half of the clusters showing the
mid-level ridge still over the northeast and the second half showing
the trough moving through. As you can imagine, there is a good deal
of uncertainty with the timing and overall amplitude, being 5 to 7
days out, there are plenty of time to watch this evolution.

Precipitation: Generally dry weather is expected during the extended,
but a weak low pressure system associated with a mid-level shortwave
does provide some assent late Sunday into Monday, the issues is the
lack of available moisture with PWATs less than 1/3". Nevertheless,
a couple of upslope flurries across western MA are possible, but a
low probability. As mentioned, by the middle part of next week there
are unsettled conditions. But there are still questions on whether
the forcing arrives with the greatest moisture content. So it is too
early for exact details, but do think this could be the next chance
for any precipitation of substance for southern New England. During
this time PWATs increase to 0.8" to 1.2", which are between 1.5 and
2.0 standard deviations above normal. A good chance the PType would
be plain rain as thermal profiles are above freezing at the surface
and up to ~800mb. Colder air advects in sometime there after into
Thursday. Do not lock anything in just yet, there is a ton of time
between now and then, but be aware of the potential for unsettled
conditions leading up to the Thanksgiving holiday.

Temperatures: Continued cooler than normal temperatures Sunday into
Monday with 850mb temperatures around -5C to -3C. 850mb temperatures
warm Tuesday and Wednesday, given the spread in guidance leaned on
the warm anomaly/signal versus the exact numbers. Sunday and Monday
highs reach the mid-40s to 50F, with lows in the 30s. Tuesday, highs
return to the low 50s, then the warmest day of next week potentially
Wednesday in the upper 50s to 60F.

&&

.AVIATION /07Z FRIDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

06z TAF Update...

Today...High confidence.

Low end VFR to high end MVFR deck moves west to east this
morning and sticking around much of the day. Winds turn SW
today at 5-10 knots with gusts to 15-20 knots possible

Friday night...Moderate confidence.

VFR/MVFR. Light SW winds

Saturday...Moderate Confidence

Area of low pressure passes to the south and may bring rain and
MVFR CIGS to the south coast and Islands. Otherwise VFR with
winds turning NW.

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 in the afternoon.

KBDL Terminal...High confidence in TAF.

VFR with periods of MVFR possible. Winds turn SW tomorrow at
5-10 knots.

Outlook /Saturday Night through Tuesday/...

Saturday Night: VFR. Breezy.

Sunday through Monday Night: VFR.

Tuesday: VFR. Chance RA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Saturday... High confidence.

* Weak system brings showers to southern waters late tonight into
  early Saturday.

* Wind and seas remain below advisory criteria through the weekend.

High pressure across the waters today shifts to the east overnight
as a weak wave of low pressure passes the south. As a result, rain
showers across the southern waters and continued weak pressure
gradient keeping winds and seas below Small Craft Advisory
thresholds through Saturday. Surface high pressure returns for the
end of the weekend.

Outlook /Saturday Night through Tuesday/...

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

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

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

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

Tuesday: Winds less than 25 kt. Chance of rain.

&&

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

&&

$$

SYNOPSIS...Dooley/KP
NEAR TERM...KP
SHORT TERM...KP
LONG TERM...Dooley
AVIATION...Dooley/KP
MARINE...Dooley/KP