429
FXUS61 KBOX 220319
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1019 PM EST Tue Jan 21 2025

.SYNOPSIS...
An arctic airmass will persist through Wednesday night with
moderating temperatures Thursday into the weekend although still
below normal temperatures. An ocean storm tracking well south
of New England may bring light snow accumulations to the outer
Cape and Islands tonight followed by clearing Wednesday.
Generally dry conditions are expected during the end of the week
and into next weekend, but we will have to watch another
distant ocean storm Thursday night which could bring light snow
to SE New England if it tracks further north and west.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
1015 PM update...

Light snow has developed across the Cape/Islands but rather dry
air in low levels not allowing this snow shield to push much
further northward. May see a few flurries along the south coast
of RI and MA, otherwise best chance of minor accum of an inch
or 2 will be over the outer Cape and Nantucket, with a coating
to an inch across the rest of Cape Cod. Snow will be moving
offshore 07-10z.

Otherwise, clearing has overspread western MA and the clearing
line will advance eastward overnight with skies clearing from NW
to SE. Temps have plummeted in western MA with the clearing and
light winds, with readings already zero to -5F. Expect temps to
fall sharply after midnight further E as skies clear. Lows will
range from zero to -10F across interior MA but locally as cold
as -10 to -15F in the Berkshires, with single numbers across
much of the rest of the region.

Previous discussion...

Key Messages:

* Frigid evening to early morning temperatures with apparent
  temps 5 to 10 below. Cold Weather Advisories for the
  Berkshires with apparent temperatures forecast near 15 to 20
  below zero.

* Minor (up to 2") snow accumulation for the Islands, with
  flurries or periods of light snow showers amounting to an
  inch or so for Cape Cod overnight.

Main change with this update was to reduce PoP over Cape Cod
some, which also naturally led to reductions in snow
accumulations (which were already on the low side) for the
Cape.

Expansive shield of midlevel cloud cover on rather strong
SWly 500 mb flow and midlevel moisture advection ahead of a
shortwave disturbance coming out of the Alleghany Mtns in WV.
Although the regional radar composite shows some echoes, this is
all sampling midlevel cloud cover with current rather large
temperature-dewpoint spreads some 15-20 degrees. As winds come
around to WNW late this evening and overnight and allows for
lower dewpoints to advect in, it`s not likely we`ll saturate
enough to allow for much in the way of precip at least to Cape
Cod. It could be enough to wring out some flurries in Barnstable
County, but I`m not thinking conditions are enough to sustain
persistent light snow. The best chance for minor accums look to
be confined to MVY/ACK overnight, but that is also still a
little unclear - it`s not likely to be any worse than a couple
inches.

But otherwise, the larger story for the rest of Southern New
England is the frigid temps. Didn`t make many changes there with
the coldest readings expected over northern/northwest MA. As was
the case last night, a fresh snowpack at night really helped to
bottom out temps and see no reason that shouldn`t again be the
case.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH WEDNESDAY NIGHT/...
Tomorrow and Tomorrow Night

Key Messages

    * Bitter cold continues tomorrow and tomorrow night

Any remaining snow over The Cape/Islands tapers off over The
Atlantic shortly after sunrise. Bitter cold continues tomorrow with
high temperatures once again suppressed to the upper teens/low 20s
with a modest west/northwest breezing making it feel closer to
single digit temperatures for most. Unlike today however, there will
be abundant sunshine with a bone dry atmosphere characterized by
PWATs around a tenth of an inch or less.

A pattern change takes place tomorrow night as high pressure to the
south slides off the east coast supporting south/southwesterly flow
and WAA into southern New England. This will support increasing
cloud cover tomorrow night and an uptick in 925 hPa temps to -10 to -
15C. While still cold, low temps tomorrow night aren`t expected to
meet advisory criteria anywhere, but will still be in the single
digits/low teens across the region. A few locations across the
interior will see wind chills fall below 0while the rest of the
region will feel like the low to high single digits.

&&

.LONG TERM /THURSDAY THROUGH TUESDAY/...
Key Messages:

* Other than passing snow showers Thurs night/Fri and possibly again
  on Sun/Sun night, dry weather is expected.

* Recovery in temps closer to seasonable Thurs, then cooling off to
  below normal levels Fri and Sat before rebounding back to
  near/slightly above normal for Sunday.

* Early next week outlook favors continued drier but cooler than
  normal weather.

Details:

Southern New England will be entrenched in what is climatologically
the coldest portion of the calendar year during this forecast
period.

Overall this forecast period will be governed by the northern stream
of a split-flow pattern at 500 mb, with mean troughing over the
central and northeastern US and a trough/closed low feature over the
southwest CONUS. Though we will have a couple of progressive Clipper
type low pressure systems moving through during this period of time,
one Thurs night/Fri and the other around Sun/Sun night, both of
these features appear to be lacking in the moisture department.
Other than passing snow showers with each, the main effect these
Clippers would have is to offer briefly enhanced cloudiness with
reinforcing shots of somewhat colder than normal temperatures in
their wake. Significant impacts are not expected with either of
these waves of low pressure, and much of the time should end up
bring dry.

Temperatures will start off "warming" up Thurs, which is really just
a rebound out of the frigid early to midweek, and highs should be
closer to seasonable levels with highs in the upper 20s to mid 30s
and lows in the 20s. Passage of the first Clipper system then brings
a period of colder than normal temperatures (e.g. highs mid 20s to
around freezing with lows in the single digits Fri night). But this
shot of cold air does not look to be nearly as stout as the colder
airmass working its way over Southern New England today. Warmest day
of this period then takes place on Sunday with highs in the low to
mid 30s with some sunshine ahead of the 2nd clipper system, which
then cools us off into early next week.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
Forecast Confidence Levels:

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

00Z TAF Update:

Tonight...High Confidence

VFR across the interior with winds becoming light out of the
west/northwest. -SN expected over ACK with periods of MVFR
ceilings and perhaps IFR vsbys, especially at ACK. Expect snow
to taper off before 12Z.

Tomorrow....High confidence.

VFR. NW wind 5-15 kt.

Tomorrow Night...High Confidence

VFR. Winds becoming light out of the west/southwest.

KBOS TAF...High Confidence in TAF.

KBDL TAF...High Confidence in TAF.

Outlook /Thursday through Sunday/...

Thursday: VFR. Breezy.

Thursday Night through Friday Night: VFR.

Saturday through Sunday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels:

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

Tonight through Wednesday night...

W winds 10-20 kt becoming NW-N later tonight into tomorrow. A
few gusts over 20 kt possible late tonight and early Wed. Arctic
airmass will result in areas of light freezing spray tonight
into tomorrow morning. Expect periods of light snow over the
south coastal waters tonight through tomorrow morning,
especially southeast of Nantucket.

Outlook /Thursday through Sunday/...

Thursday: Winds less than 25 kt. Slight chance of rain.

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

Friday through Saturday: Winds less than 25 kt.

Saturday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 25 kt. Seas up to 5 ft.

Sunday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...Cold Weather Advisory until 10 AM EST Wednesday for MAZ002-008-
     009.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...Loconto/RM
NEAR TERM...KJC/Loconto/RM
SHORT TERM...RM
LONG TERM...Loconto
AVIATION...Loconto/RM
MARINE...Loconto/RM