175
FXUS61 KBOX 210706
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
206 AM EST Sun Dec 21 2025

.WHAT HAS CHANGED...
No significant changes. Minor snow accumulations still expected Tue,
especially in the interior. Low confidence temp and precip forecast
for Friday and Saturday.

&&

.KEY MESSAGES...

- Dry and blustery today as temperatures plummet tonight into
  Monday.

- Minor snow accumulations of 1-3" possible Tue, especially
  interior.

- Mainly dry and seasonable Wed & Thu. Blustery Wed with lighter
  winds Thu.

- Low confidence temp and precip forecast for Fri and Sat but
  trending colder Sat.

&&

.DISCUSSION...

KEY MESSAGE 1...Blustery today, then temperatures plummet tonight
into Monday.

Gusty SW winds have already begun to arrive ahead of the frontal
passage, especially along the coast and Islands where better mixing
is present. Expecting to see gusts around 25-35 mph. Should see a
lull in the winds for a few hours as the front passes through, then
another 45kt low level jet pushing in behind the front. This LLJ
will bring a secondary round of 25-35 mph gusts later tonight into
Monday morning. Winds gradually diminish through Monday as the
pressure gradient weakens.

Moderate temperatures this afternoon ahead of the front, then
temperatures plummet behind the front later tonight. 850 mb temps
bottom out around -12C to -15C. Wind chills by Monday morning will
range from single digits in the interior to mid teens across the
Cape/Islands... except slightly below zero in the Berkshires.
Monday`s temperatures will be several degrees below normal with
highs in the upper 20s to lower 30s and plentiful sunshine in very
dry airmass.

KEY MESSAGE 2...Minor snow accumulations possible Tue.

A shortwave will be moving into the region while a warm front
approaches from the SW. Given NW flow aloft, it is likely the warm
front will remain to the west of SNE which keep the region in the
colder air aloft ensuring snow to start for all SNE. There is some
uncertainty with timing of snowfall as GFS has shifted timing more
to Tue afternoon and especially Tue night, however global ensemble
guidance has Tue as most favorable period of snowfall so expecting
snow to develop by Tue morning. But developing onshore flow expected
to warm the boundary layer especially south and east of I-95 where
snow may transition to a mix or rain for a time by late morning or
afternoon. It is possible snow or mixed snow/rain will linger into
Tue evening, but this is not a significant QPF event so expecting
mostly light accumulations on the order of 1-3 inches in the
interior and an inch or less closer to the coast. Confidence is
moderate but will have to watch for low pres developing on the front
near or south of SNE which could enhance precip with a low risk for
somewhat higher accums. This is a low prob scenario as even 90th
percentile of snowfall from GEFS, EPS and Canadian ensembles are
just 1-2" near the coast and 2-4" further inland.

KEY MESSAGE 3...Mainly dry and seasonable Wed & Thu. Blustery
Wed with lighter winds Thu.

Low pres will deepen well east of New Eng on Wed leading to gusty
NW winds but dry weather, then lighter winds Thu as high pres
moves into New Eng. There is a boundary that sets up to the SW
Thu but deeper moisture is expected to remain to the south and
west so mainly dry weather. Temps Wed will be a bit below normal
with highs mostly in the 30s, with slight moderation Thu in the
upper 30s to lower 40s near the south coast.

KEY MESSAGE 4...Low confidence temp and precip forecast for Fri
and Sat but trending colder Sat.

Low confidence forecast for Fri and Sat as polar jet will be over
New Eng with more shortwave energy approaching and global guidance
showing significant spread on where a boundary will set up and track
of low pres. As previous forecaster mentioned, there will be quite a
thermal gradient from north to south across New Eng and mid Atlc
region and location of the boundary will be critical to temps and
sensible weather. Potential outcomes for Fri range from temps into
the 50s and wet weather if boundary is to the north, to temps in the
20s and 30s and dry if boundary is well to the south.  There is
higher confidence the boundary will be south of New Eng Sat with
much colder temps but uncertainty if moisture will return. Bottom
line, there is very low confidence for Fri and Sat and would expect
significant modifications to the forecast going forward.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...

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

Today through Monday...High Confidence.

VFR through the period, but patchy MVFR cigs early this morning
over the Cape and Islands. SW gusts 25-35 kts this morning,
especially along the immediate coast, Islands, and higher
terrain. Winds turn NW and gusty this afternoon into tonight
post-FROPA, then gradually diminish Monday.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Monday Night through Thursday/...

Monday Night: VFR. Chance SN.

Tuesday: Mainly IFR, with local MVFR possible. Breezy. SN
likely, RA.

Tuesday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SN.

Wednesday: VFR. Windy with local gusts up to 30 kt.

Wednesday Night: VFR.

Christmas Day: VFR. Breezy. Slight chance RA.

&&

.MARINE...
Forecaster Confidence Levels...

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

Today through Monday...High Confidence.

Marginal Southwesterly gales this morning ahead of a cold
front with gusts 25-35 kts expected. Winds shifting to NW this
afternoon with 25-35 kt gusts persisting into Mon morning
before diminishing. Seas 7-10 ft over the outer waters will
begin to subside during Monday.

Outlook /Monday Night through Thursday/...

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

Tuesday: Winds less than 25 kt. Local rough seas. Rain likely,
chance of snow. Areas of visibility 1 to 3 nm.

Tuesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Areas of rough seas. Chance of rain.

Wednesday: Strong winds with gusts up to 35 kt. Rough seas up
to 11 ft. Slight chance of rain.

Wednesday Night: Winds less than 25 kt. Areas of rough seas.

Christmas Day: Winds less than 25 kt. Local rough seas. Slight
chance of rain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST Monday for ANZ230-236.
     Gale Warning until 7 AM EST Monday for ANZ231>235-237-250-251-
     254>256.

&&

$$

DISCUSSION...KJC/McMinn
AVIATION...McMinn
MARINE...KJC/McMinn