399
FXUS61 KBOX 041737
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1237 PM EST Thu Dec 4 2025

.SYNOPSIS...
An arctic cold front crosses the region today with a few snow
showers and a localized snow squall or two, particularly for
western MA. Windy conditions and bitterly cold temperatures
tonight. The winds quickly diminish by Friday, but it remains
unseasonably cold. Scattered snow showers possibly mixing with
rain showers late Friday night into Saturday with a low pressure
system passing well to our south. Another arctic cold front
crosses the region Sunday followed by well below normal
temperatures Sunday night into Tuesday. A low pressure system
approaching from the west may bring some more rain/snow showers
by Tuesday night and/or Wednesday.

&&

.NEAR TERM /THROUGH TONIGHT/...
Key Messages:

* Arctic cold front passes through southern New England, bringing
  scattered snow showers and the chance for localized snow squalls

Not much has changed for today from the previous forecast. An arctic
cold front will cross over southern New England this afternoon. Some
clouds and sunshine before that should bring highs up to the 30s and
low 40s. Forecast soundings from the high-res guidance still
indicate dry low to mid levels across much of the region, though
snow squall parameter values from the NAM and GFS do remain
elevated. Lapse rates and some elevated instability could point more
favorably for the development of localized snow squalls,
particularly in NW MA, but the key limiting factor will still be the
drier air aloft. Scattered snow showers with some flurries are more
favored elsewhere as the front passes through.

As the front moves through, winds will pick up from the NW. Gusts
between 25-40 MPH can be expected during the late afternoon hours,
continuing through the evening into the first half of tonight.

&&

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

* Bitterly cold with lows well below normal in the single digits and
  wind chills between -10F and +10F

* Unseasonably cold conditions continue for Friday

Gusty NW winds fall off over the second half of tonight as high
pressure starts to creep in from the west. 925 mb temperatures fall
between -15C and -18C as the arctic airmass behind the day`s front
moves over the region. Wind chills could fall to -10F in some spots
in NW MA. Skies also clear out tonight, and if winds diminish
enough, this combined with the snowpack could be enough for lows to
fall below zero there. Elsewhere, wind chill values could end up
maxing out at +10F with lows in the teens and single digits.

High pressure builds in from the west during the day Friday. Sunny
skies with light winds will prevail, but high temperatures are still
expected to be colder than normal for this time of year. 925 mb
temperatures do improve to between -8C and 10C, but given limited
mixing during the day, high temperatures stay in the 20s and low
30s.

&&

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

* Scattered snow/rain showers possible late Fri-Saturday,
  potentially changing over to rain Sat, especially east of I-95.
  Any snow accumulation likely to be minor.

* Another shot of arctic air Sun night into Tue with well below
  normal highs and very chilly nights in teens/single digits.

Details...

Friday Night & Saturday:

High pressure shifts offshore by Friday night as a weak shortwave
trough approaches southern New England. An associated surface low
tracks off the mid-Atlantic coast, passing to the south and east of
the region Friday into Saturday. This will bring the risk for some
scattered snow or rain showers. Without a strong, anchored cold air
mass, there is a chance for rain to mix in, potentially changing to
rain showers (Inside I-95, SE MA) in the afternoon. Snow
accumulations will be light with ensembles means showing amounts
less than an inch. Total QPF is on the light side as well (< 0.25")
with the highest chances for precip (rain) for the Cape/Islands.
Model guidance continues to show an inverted trough positioned
across the region late Fri into Sat with subtle hints of convergence
in the wind fields. This could potentially provide better forcing
for a more organized band of precipitation. Can`t rule out a brief
deformation-type band on the backside of the system later Saturday
as cooler air pushes in from the west. Details still to be ironed
out for timing of these more organized bands of showers and precip
type. Temperatures will lean slightly below normal Saturday in the
30s and low 40s for the Cape/Islands.

Sunday through Wedneday:

Another weak shortwave in the zonal flow aloft moves through Sunday,
with another arctic front sweeping across Sunday night-early Monday.
Most of Sunday should be dry with highs in the mid-upper 30s and low
40s for the Cape/Islands. Can`t rule out a snow shower/flurry Sunday
night with the passage of the arctic front. No concerns for impacts.

Below normal temperatures and breezy NW winds on Monday with highs
in the 20s to low 30s and wind chills in the teens. Below normal
temperatures continue Tuesday, although slightly moderated from
Monday with highs in the mid-upper 20s for the higher elevations and
30s elsewhere. Confidence in the pattern decreases toward mid-week,
but there are indications of a another weak disturbance moving
through later Tuesday into Wednesday with potential for showers.
Details are still uncertain (timing, amounts, precip type), but will
become more clear as we gain a better consensus on the upper level
pattern.

&&

.AVIATION /18Z THURSDAY THROUGH TUESDAY/...
Forecaster Confidence Levels...

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

18Z TAF Update:

Through 00z Friday: High confidence in TAF/trends but moderate
on coverage of snow showers/squalls.

VFR for most of this period. An Arctic cold front could bring
brief convective snow showers or possible snow squalls from BAF
to BOS north and west mainly 19-23z. Indicated with VCSH and
will proactively AMD for tempo SHSN & IFR visbys. If any visbys
were to be reduced it would mainly be for an hour or less, with
any accumulation limited to coatings due to their brief nature.
We then get a gusty NW windshift upon frontal passage, with
speeds 15-20 kt and gusts 32-38 kt.

Tonight: High confidence.

VFR. Gusty NW winds 30-35 kt thru 04z, then a slow decrease in
gusts to around 20-25 kt overnight. After 08z, could see some
MVFR ceilings over the Outer Cape and Nantucket (mainly HYA/ACK)
with possible flurries at times due to ocean effect cloud
cover/narrow bands of ocean effect precip.

Friday: High confidence.

VFR with ocean effect VFR/MVFR ceilings HYA/ACK and the Outer
Cape thru about 16-18z as winds remain NW around 5-10 kt.
Windshift to S during the afternoon will shut off ocean
effect cloudiness, but will begin to bring a layer of VFR/MVFR
bases from the ocean waters to BID and perhaps immediate south
coast, Cape and Islands by sundown.

Friday Night: Moderate to high confidence.

VFR initially, though a shallow layer of VFR/MVFR cloud decks
advance northward from the southern waters. Low prob of SHSN or
possible very spotty FZDZ south of PVD underneath this as layer
aloft is dry. Light south winds.

KBOS Terminal...High confidence in TAF. Low for SHSN chances.

KBDL Terminal...High confidence in TAF. Moderate for SHSN
chances.

Outlook /Saturday through Monday/...

Friday Night: Mainly VFR, with local MVFR possible. Slight
chance SN.

Saturday: Mainly VFR, with local MVFR possible. Slight chance
RA, slight chance FZRA, slight chance SN.

Saturday Night through Sunday: VFR.

Sunday Night through Monday: VFR. Breezy. Slight chance SN.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Friday...High confidence.

* Gale Warnings this afternoon and tonight

The main concern will be an arctic cold front that crosses the
region today. This will bring NW wind gusts of 30 to 40 knots
this afternoon and tonight. This has prompted the issuance of
Gale Warnings for our waters given excellent mixing given the
amount of cold air crossing the relatively warm waters. High
pressure quickly builds in from the west Fri allowing winds/seas
to diminish significantly.

Outlook /Saturday through Monday/...

Friday Night: Winds less than 25 kt. Slight chance of rain.

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

Saturday Night: Winds less than 25 kt. 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.

Monday: Strong winds with gusts up to 30 kt. Seas up to 5 ft.
Slight chance of rain, slight chance of snow.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Gale Warning from 4 PM this afternoon to 1 AM EST Friday for
     ANZ230-236.
     Gale Warning until 4 AM EST Friday for ANZ231>235-237-250-251-
     254>256.

&&

$$

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