599
FXUS61 KBOX 021941
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
241 PM EST Tue Dec 2 2025

.SYNOPSIS...

A winter storm will bring accumulating snow across interior
southern New England into tonight...particularly north of I-90
into the high terrain where significant snow accumulations are
expected. Mainly rain is expected across eastern MA and
RI...before a transition to snow occurs later tonight. All
precipitation should have come to an end by daybreak Wednesday.
An arctic front may be accompanied by a few snow showers or
squalls Thursday followed by very cold airmass Thursday night
and Friday. A coastal storm tracks well to the south Friday
night and Saturday but may bring a bit of light snow to the
region. Another cold front moves through Sunday followed by
another surge of very cold air Sunday night and Monday. Mainly
dry and cold conditions continue into Tuesday.

&&

.NEAR TERM /THROUGH TONIGHT/...

Key Messages...

* Winter Storm continues tonight across interior southern New
  England especially north of I-90 and the high terrain

* 1-2" per hour snowfall rates north of I-90 and especially near
  route 2 make for hazardous travel for the evening commute

* Mid level warm layer moving northward will result in Ptype
  transitioning to a period of rain/ice south of I-90

* Narrow swath of sleet and freezing rain for a time into
  northern CT, interior southern MA and far northwest RI

* Mainly rain along the I-95 corridor into RI that should transition
  to a period of snow before ending toward daybreak

* Total snow accumulations of 5-10" in the highest terrain of
  northern MA...2-5" in the lower elevations of western/central
  MA...and mainly a dusting to 2" across RI and eastern MA

Details...

This afternoon into tonight...

Low pressure will be intensifying as it moves off the mid Atlantic
coast and tracks just inside the Benchmark this afternoon into this
evening. Thermal profiles are initially cold enough for mainly snow
northwest of the I-84/I-495 interchange inland from the coastal
front into mid afternoon. However...given the lack of cold high
pressure across eastern Canada and the mid level centers tracking
northwest of the Benchmark will allow warmer mid-level air to move
northward. Therefore...an initial burst of snow through early
afternoon will change to mainly rain south of I-90 by mid-late
afternoon. A few inches of snow may occur in this region before the
transition to rain across southwest/south central MA perhaps into
far northern CT. There remains some uncertainty how far north this
mid level warm layer will reach before stalling out...but we are
thinking this will mainly stay south of the route 2 corridor and
possibly not make it much further north than I-90. As the mid level
low/s close off and result in strong mid level frontogenesis...we
may see 1-2 per hour snowfall rates this afternoon into early
evening where Ptype remains snow north of I-90 and especially
towards route 2. This will result in significant impact to the
evening commute north of I90 and especially near route 2 corridor.

There is a narrow area of sleet and freezing rain on the edge
of the mid level warmth. We did expand the Winter Weather
Advisory into northern CT/far northwest RI to account for this
risk. We also are seeing this  sleet and freezing rain into
interior parts of southern MA near and south of I-90.
Meanwhile...areas south of I-90 as well as along the I-95 should
see moderate to heavy rain for the late day commute.

As the mid level low/s shift east of the region...lingering moisture
with temps cooling aloft should allow for many locations to
transition to snow before things wind down before daybreak
Wednesday. A coating to an inch of snow will be possible onto the I-
95 corridor with perhaps 2" into interior eastern MA. Further
northwest in the lower elevations of western/central MA and even
interior northeast MA...total accumulations of 2-5" seem
reasonable. The highest snowfall amounts of 5-10" should be
common across the northern Worcester Hills/Berks and as well as
areas north of route 2.

Lastly...gusty N winds will work into the region on the backside of
the system later this evening and overnight. Gusts of 20-30 mph are
expected overnight with some 35-40+ mph gusts possible across
the outer- Cape/Nantucket. Low temps by daybreak will be in the
20s across the interior...with lower to middle 30s along the
I-95 corridor and middle to upper 30s near the Cape and Islands.
So not expecting many issues with roads along and southeast of
I-95 corridor...but northwest of I-95 untreated roads will be
slippery for the Wed am commute despite the precipitation having
ended.

&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...

Key Messages...

* Mostly sunny/quiet weather Wed with highs ranging from the middle
  30s in the high terrain to the upper 30s/lower 40s elsewhere

* Dry and chilly Wed night with lows in the upper teens and 20s

Details...

Wednesday...

A ridge of high pressure briefly builds to our southwest on
Wednesday. This will result in plenty of sunshine with winds
becoming rather light by later in the morning and afternoon.
Temperatures still below normal for early December...but not
bad with plenty of sunshine and light winds. Highs Wednesday
should range from the middle 30s in the high terrain and the
upper 30s to the lower 40s elsewhere.

Also...we did opt to issue a Coastal Flood Statement for the high
astro tide Wednesday morning along the eastern MA coast. Any
impacts should be very minor...but with building seas offshore
and a gusty N- NW winds some very minor coastal flooding/splash
over will be possible during the time of high tide with the best
chance south of Boston.

Wednesday night...

Dry and chilly weather is on tap for Wednesday night out ahead of an
arctic cold front. Low temperatures should mainly be in the upper
teens and 20s.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...

Key Messages:

* Scattered snow showers and localized squalls possible Thu

* Arctic airmass moves into SNE Thu night-Fri with very cold temps

* Coastal storm to the south may bring some light wintry precip Fri
  night and Sat but bulk of precip expected to remain to the south.
  Minimal impacts expected

* Another cold front will deliver a very cold airmass Sun night-Mon

Overview...

Overall -AO/-NAO pattern will persist through the extended period
keeping mean trough across the eastern CONUS with TPV over eastern
Canada. This will keep temps well below normal with a few surges of
arctic air. Overall, not looking at any significant precip events
through the period with northern stream dominant pattern and minimal
southern stream interaction.

Details...

An arctic front crosses the region Thu afternoon and evening and
will likely be accompanied by scattered snow showers. The snow
squall parameter is favorable Thu afternoon, especially across
northern MA as the front is moving so potential exists for a few
localized snow squalls. After the front moves through, gusty NW
winds during the afternoon and evening will usher in much colder air
with sharply falling temps. Winds diminish overnight as high pres
builds over New Eng with cold advection transitioning to radiational
cooling for the second half of the night. 925 mb temps bottom out
around -14 to -16C Thu night and recover to -8 to -10C on Fri. Lows
will drop into the single numbers interior and teens in the coastal
plain. High pres in control Fri with dry and cold weather and highs
mostly in the 20s, except lower 30s near the south coast.

Fast moving low amplitude shortwave moving off the mid Atlc coast
with coastal low tracking well to the south Fri night into Sat. Best
moisture and bulk of QPF remains to the south but can`t rule out a
bit of light snow Fri night, especially south of the MA Pike, then
some light rain/snow showers possible during Sat. Ensemble guidance
indicates potential for a very light QPF event with minor accum less
than an inch possible with minimal impacts expected.

Another cold front will be moving through Sun with another surge of
arctic air Sun night into Mon with lows down into the single numbers
and teens again and highs Mon in the 20s to lower 30s. Mainly dry
weather Sun-Mon. Temps moderate some next Tue and it still looks dry
but confidence in sensible weather is low given considerable spread
in the guidance with timing, amplitude and location of approaching
shortwaves.

&&

.AVIATION /19Z TUESDAY THROUGH SUNDAY/...

Forecaster Confidence Levels...

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

18Z update...

Today...Moderate Confidence.

MVFR ceilings drop to IFR-LIFR as precip overspreads the region
this afternoon, 18-21z. Ptype rain for coastal terminals. SN
to start for BDL,BAF, BED, and ORH, with chance for RA to mix
in the afternoon 19z-21z. Lower confidence for precipitation
type due to uncertainty in location of rain-snow line. E-NE wind
5-15 kt. Minor accumulations for BDL, BAF, BED, and ORH. 2-6"
possible depending on where RA- SN line positions. Snowfall
rates less than 0.5"/hour for terminals.

Tonight...Moderate confidence.

Widespread IFR-LIFR improving to VFR late from west to east
after 06Z. Light SN for interior terminals in evening. Change
over to a period of light RA/SN or light SN possible along the
I-95 corridor, including BOS and PVD for a short period. Timing
of change over is lower confidence, but would be after 03Z.
Minor accum (Trace-0.5") possible at BOS. NE wind becoming N-NNW
with gusts to 25 kt developing, with 30-40 kt gusts possible
for Cape/Islands.

Wednesday...High Confidence.

VFR. NW winds with gusts up to 22 kts (up to 25 kts for
Cape/Islands) in the morning decreasing in the afternoon.

KBOS Terminal...Moderate confidence in TAF.
Changeover to -RASN or -SN possible Tuesday night. Exact timing
lower confidence, more likely between 03-07z.

KBDL Terminal...Moderate confidence in TAF. Lower confidence in
timing of ptype changes.

Outlook /Thursday through Sunday/...

Thursday: VFR. Windy with gusts up to 35 kt. Slight chance
SHSN.

Thursday Night: VFR. Windy with gusts up to 35 kt.

Friday: VFR. Breezy.

Friday Night: VFR. Slight chance FZRA, slight chance SN.

Saturday: VFR. Chance RA, slight chance SN.

Saturday Night through Sunday: VFR.

&&

.MARINE...

Forecaster Confidence Levels...

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

Tonight...High confidence.

* Gale warnings tonight across our eastern waters

Rapidly intensifying low pressure system passes east of the
Benchmark this evening. This increase in pressure gradient results
in N wind gusts increasing to between 30 and 40 knots. Strongest of
those winds will be across our eastern waters where Gale Warnings
will continue. Across our western waters...strong small craft
advisories remain posted but a few brief gusts to 35 knots possible.

Wednesday and Wednesday night...

The low pressure system will already be east of the Canadian
Maritimes Wednesday morning. A weak ridge of high pressure will then
temporarily build to our southwest. This will allow winds to
diminish Wed and while seas will slowly drop off too...they will
remain elevated enough that small craft headlines will be needed
into early Wed evening. Winds/seas may both briefly drop below small
craft thresholds later Wed night...but SW wind gusts of 20-25 knots
will re-develop toward daybreak Thu ahead of our next cold front.

Outlook /Thursday through Sunday/...

Thursday: Low risk for gale force winds with gusts up to 40 kt.
Areas of rough seas. Slight chance of rain showers.

Thursday Night: Moderate risk for gale force winds with gusts
up to 40 kt. Rough seas up to 10 ft.

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

Friday Night: Winds less than 25 kt. Chance of rain, chance of
snow.

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

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

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...Winter Weather Advisory until 7 AM EST Wednesday for
     CTZ002>004.
MA...Winter Weather Advisory until 7 AM EST Wednesday for MAZ005-
     006-010>012.
     Winter Storm Warning until 7 AM EST Wednesday for MAZ002>004-
     008-009-026.
RI...Winter Weather Advisory until 7 AM EST Wednesday for RIZ001.
MARINE...Gale Warning from 7 PM this evening to 7 AM EST Wednesday for
     ANZ230.
     Gale Warning from 7 PM this evening to 1 PM EST Wednesday for
     ANZ231-232-250-251-254-255.
     Small Craft Advisory until 7 PM EST Wednesday for ANZ233>235-
     237.
     Small Craft Advisory until 7 AM EST Wednesday for ANZ236.
     Small Craft Advisory until 1 AM EST Thursday for ANZ256.

&&

$$

SYNOPSIS...Frank/KJC
NEAR TERM...Frank
SHORT TERM...Frank
LONG TERM...KJC
AVIATION...Dooley/KJC
MARINE...Frank/KJC