308
FXUS61 KBOX 052016
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
316 PM EST Fri Dec 5 2025

.SYNOPSIS...
Increasing cloud cover tonight with temperatures gradually
warming overnight. Overcast on Saturday, with possible very
light snow or rain showers duirng the first part of the day
before clouds decrease Saturday evening. Dry on Sunday before
another arctic cold front crosses the region overnight with a
chance for a few snow/rain showers. Well below normal
temperatures Monday before slowly moderating Tuesday/Wednesday.
More unsettled overall next week with a few disturbances moving
through bringing periodic chances for rain/snow showers late
Tue-Wed and Wed-Thu.

&&

.NEAR TERM /THROUGH SATURDAY/...
135 PM Update:

Key Messages:

* Clear early tonight, but increasing low clouds overnight.
  Gradually warming temps overnight.

* Overcast with possible spotty very light snow/snowflakes,
  very light rain or spotty freezing drizzle Sat morning. Accums
  are nil, and light snow or freezing drizzle types probably
  not persistent enough for any impact.

* Skies start to clear late in the day.

Details:

Temperatures this afternoon, coming out of a frigid overnight
have recovered only into the 20s this afternoon across Southern
New England. Thus it marks the first widespread subfreezing day
thus far in the winter months. Clear skies will initially govern
Southern New England through the rest of the afternoon into
early tonight; however there are two areas of low clouds, one
offshore of south coast, and the other working its way northward
from the Poconos in east PA/lower Hudson Valley in NY. This is
occurring in response to a shallow warm/moist layer returning
northward. Expect early lows in the mid teens to lower to mid
20s before the low clouds/stratus layer advects northward. When
that happens - thinking most areas trend overcast by midnight,
and even sooner along the south coast and into CT/RI - temps
then begin to rise into the 20s to around freezing by daybreak.

Overcast continues into a good part of Sat, which will
effectively slow the rate of temperature rise despite a
continued modest warm advection pattern. Where there are some
question marks in the forecast is with regard to possible
impact, if there is any at all, from either spotty very light
snow, very light rain or spotty freezing drizzle; with this
threat being during the pre-dawn hrs overnight tonight into the
Sat morning hours. Particularly in the high-res models, there`s
some hints at an N to S inverted trough which could focus some
of this activity, though it`s not as defined if present at all
in the global models. With an unsaturated ice crystal nucleating
layer (around -10 to -18C, can be lower near the ocean) atop
the layer of stratus, drizzle/freezing drizzle types can`t be
discounted. BUFKIT soundings show a layer of high clouds which
could help to support snowflakes in a process called "seeder-
feeder", where high clouds provide the ice nuclei to "seed" the
lower-level stratus deck for snowflakes. But if you`re reaching
that deep into the well, that`s not typically a scenario which
garners any accumulations and we don`t expect any in this case.

What we think will happen is you`ll see intervals of snowflakes
or "snizzle" (snowflakes mixed with freezing drizzle) early Sat
AM to about noontime, but the persistence of either type
probably won`t be enough to yield impacts in the form of
slippery roads. These situations are lower-probability and later
shifts could consider an SPS for this if it looks more likely
we see more persistent bands of precip. Portions of eastern MA,
eastern CT and RI could be more vulnerable as roads in northern
CT/western-central MA probably were treated coming out of the
early-week snow event. Forecast shows nil accums. Highs Sat
mainly in the 30s.

&&

.SHORT TERM /SATURDAY NIGHT/...
135 PM Update:

Key Message:

* Clearing skies, dry weather and turning chilly.

Details:

Skies clear out early Sat night, with clear skies and a light
WNW wind permitting some radiational cooling to take place.
Another chilly evening but nothing like what we saw Thurs
night/Fri AM. Temperatures drop into the 20s in most areas
Saturday night. If any of the existing snowpack melts some
during the daytime hours, it may refreeze.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Key Messages...

* More arctic air arrives Sunday night into the early part of next
  week before temps warm up mid week.

* A few chances for precip first late Sunday/Sunday night then
  better odds mid to late week.

Rather quiet stretch of weather to end the weekend and kick off next
week under quasi-zonal flow. Sunday features increasing clouds
through the day ahead of a weak mid-level shortwave which moves
through late Sunday/overnight. Not much excessively strong forcing
and very meager moisture around will more than likely make the
eventual cold frontal passage more dry than wet. Guidance has further
backed off on probabilities of even 0.01" of QPF with the greatest
odds in northern MA in closer proximity to the better mid level
forcing. Thus, expecting a coating to a few tenths of an inch of
snow in the high elevations. The main story for the start of the
week will be a brief shot of arctic air Monday/Monday night. 925mb
temps drop from -3C on Sunday to -13C on Monday. This, as the
pressure gradient tightens between the exiting/deepening low and the
incoming high. So wind gusts of 20-30 mph will make highs in the 20s
and low 30s feel like the teens and low 20s. This brief cool down
will give us another night (Monday night) with lows in the single
digits and low teens.

The cool down is brief as flow turns SW Tuesday ahead of another
shortwave/surface low over the midwest so highs return to the upper
30s/low 40s by Wednesday.

While guidance is in agreement that Mon/Tue mid level ridging is
brief, timing and placement of our next shortwave trough is less
certain. Probabilities for wet weather increase significantly by
Wednesday into Thursday. Next chance for some scattered showers
comes late Tuesday with more widespread showers by late Wed/Thu.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels...

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

18Z TAF Update:

Through 00z Saturday: High confidence.

VFR, though SCT MVFR bases from the southern ocean waters could
approach the Cape terminals in the 23-00z timeframe. S winds
around 5-8 kt.

Tonight through Saturday: Moderate to high confidence.

VFR for a brief period of time early tonight. Shallow layer of
BKN/OVC MVFR stratus to expand gradually northward from the
southern waters and/or the lower Hudson Valley, soonest
(~00-01z) for the Cape and Islands and later (~04-05z) for
BED/BOS. S winds turn light/calm.

Confidence is reduced to moderate is with regard to potential
for moisture to wring out light -SN, patchy -FZDZ, or -RA
underneath the stratus layer. Accumulating or measurable precip
isn`t expected with either type. We opted for PROB30 of -SN/RASN
in TAFs, since -FZDZ coverage probably won`t be persistent
enough to cause runway impacts but some -FZDZ is possible.

MVFR stratus from the overnight improves to VFR levels between
16-19z Sat from west to east. Winds then shift to light WSW/W
accompanying the improvement to VFR.

Saturday Night: High confidence.

VFR. W to NW winds around 5 kt.

KBOS Terminal...High confidence through tonight, then moderate
to high. VFR with light S winds through 05z Sat, then MVFR
stratus develops. Very light -SN or very spotty -FZDZ possible
between 09-15z Sat, although precip is so light no accums are
expected and -FZDZ probably not persistent enough for runway
impacts. MVFR cigs improve to VFR after 18z with W winds around
5 kt.

KBDL Terminal...High confidence through tonight, then moderate
to high. VFR with light S winds through 03z Sat, then MVFR
stratus develops. Very light -SN or spotty -FZDZ possible
between 09-15z Sat, although precip is so light no accums are
expected and -FZDZ probably not persistent enough for runway
impacts. MVFR cigs improve to VFR after 18z with W winds around
5 kt.

Outlook /Sunday through Wednesday/...

Saturday Night through Sunday: VFR.

Sunday Night: Mainly VFR, with local MVFR possible. Breezy.
Slight chance FZRA, slight chance SN.

Monday through Tuesday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Tranquil boating conditions expected through Saturday night,
with winds and seas below small craft advisory thresholds. S
winds around 10 kt or less today become light tonight into most
of Sat, then become W/WNW Sat night around 10 kt. Seas 3 ft or
less all waters thru Sat night.

Outlook /Sunday through Wednesday/...

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

Sunday: Winds less than 25 kt.

Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Chance of snow, slight chance of rain, slight chance of
freezing rain.

Monday: Strong winds with gusts up to 30 kt. Areas of rough
seas. Slight chance of snow.

Monday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas.

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

&&

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

&&

$$

SYNOPSIS...Loconto/BW
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...BW
AVIATION...Loconto/BW
MARINE...Loconto/BW