Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 162100
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
400 PM EST Sat Dec 16 2017

.SYNOPSIS...
Blustery and cold conditions today with less wind Sunday as
high pressure builds across the region. A weak wave of low
pressure may bring spotty light snow showers to the region late
Sunday night into Monday morning. Temperatures will be milder on
Tuesday ahead of a cold front, then turning blustery and colder
Wednesday into Thursday. A wave of low pressure which may track
to our west will bring the potential for a wintry mix/rain
sometime Friday and/or Saturday.


&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...

430 PM Update...

Moderate snow showers are beginning to move into southern New
England this afternoon. Expect these snow showers to expand across
the region as northern stream shortwave pushes into the Northeast.
This is being observed in latest GOES-16 Water Vapor Imagery. Best
chance for a quick coasting of snow remains across western and
central MA, CT, RI down into the south coast towards evening. Also
included some flurries in the forecast across northeast MA including
the city of Boston. Even through low levels are quite dry, mid-level
moisture and passing shortwave could trigger enough for some flakes
to fly. Still continue to watch for the potential of some snow
squalls late this afternoon into the evening. Best chance per BTV
WRF model is across western MA down into RI, which could lower
vsbys. Went ahead and issued a SPS for the potential of slick roads
and lower visibilities into the early evening.

Tonight...

Surface cold front will swing through from the north tonight. Behind
it, strong high pressure will follow resulting in clearing skies and
light winds. Temperatures will plummet overnight thanks to
radiational cooling. Single digits are expected across western MA
with teens everywhere else.


&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH SUNDAY NIGHT/...

Sunday into Sunday night...

High pressure north of the region will continue to build into
tomorrow. This will result in light winds and mostly clear skies. A
chilly start to the morning with temps rebounding into the upper 20s
to low 30s. Despite weak WAA during the later half of the day, still
enough shallow cold air to keep temps cooler than today. Clouds will
build within the WAA pattern during the later afternoon into evening
hours.

Surface low pressure system moving into the Great lakes with warm
front extending towards the northeast. High pressure remaining to
our north will keep winds light during the overnight hours. However
with clouds thickening during the late evening, radiational cooling
will be limited resulting in lows in the teens and low 20s.

Increasing threat-e ahead of the warm front could be enough for a few
snow showers towards the early morning. Models are indicating very
little in the way of QPF and with not a lot of lift, will keep the
potential at a chance for now.

&&

.LONG TERM /MONDAY THROUGH SATURDAY/...

* Lingering spotty light snow showers possible into Mon AM
* Low risk for spotty freezing drizzle northern and esp NE MA Mon PM
* Mainly dry and much milder Tue
* Blustery and colder with mainly dry weather Wed into Thu
* Period of wintry mix/rain possible sometime Fri and/or Sat

Details...

Monday morning...

Moisture and weak lift may be enough for a bit of lingering spotty
light snow showers into Monday morning.  Limited moisture/forcing
will should keep any accums to a dusting to no more than an inch.

Monday afternoon and night...

Somewhat of a tricky forecast Monday afternoon and night.  Low clouds
will likely hang tough on Monday. Temps should climb above freezing
Monday afternoon to the south of the MA turnpike with readings
reaching well into the 30s to the lower 40s.  North of the MA
turnpike, temps will struggle to climb much above freezing.  In
fact, some of the guidance shows a weak meso-low lifting northeast
of the region.  This may allow temps to fall a bit across parts of
the area during the afternoon, especially northeast MA where some
guidance has readings in the 20s by early evening.  Not sure if
there will be enough left over low level moisture for any precip,
but can not rule out the low risk for spotty freezing drizzle or
flurries in north and especially northeast MA Mon PM.  Something
will have to watch closely though given just trace amounts of spotty
freezing drizzle can be problematic.

Tuesday...

Westerly flow aloft, 850T near -2C and decent mixing should push
high temps well up into the 40s to perhaps even near 50 in a few
locations along the coastal plain.   Mainly dry weather anticipated
as synoptic forcing is limited, but can not rule out a few showers
in the afternoon across western MA as a cold front approaches.

Tuesday night and Wednesday...

A cold front will cross the region Tue night into early Wed with
perhaps a few brief rain/snow showers.  High temps will recover well
into the 30s to around 40, but a well mixed atmosphere should result
in northwest wind gusts of 30 to 40 mph developing Wednesday and
making it feel colder.

Thursday...

Mainly dry and cold weather continues but with less wind than on
Wednesday.  High temps will be held mainly in the lower to middle
30s.

Friday and Saturday...

Low confidence forecast as always given time range but even more
complicated by the pattern.  Model guidance has a classic La Nina
pattern with upper level ridging over the southeast U.S., resulting
in above normal temps in that region.  Meanwhile, arctic air will be
sitting across eastern Canada.  This will put our region in the
battle ground with a wide range in possible temperature outcomes and
ptypes.  Based on the current guidance an initial wave of low
pressure appears like it will track west of the region Fri into Sat.
Assuming that happens, ptype would either be mainly rain or snow/ice
transitioning to mainly rain.  Of course a lot can change between
now and that time, and given the large temperature gradient that
will be setting up across the eastern U.S. would not put to much
into a deterministic forecast this far out.

&&

.AVIATION /21Z SATURDAY THROUGH THURSDAY/...
Forecaster Confidence Levels...
Low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

Short Term /through Sunday Night/...High confidence.

Before 00z...VFR with iso MVFR from ORE to FMH in snow showers.
Gusty west winds near 25 kts higher along the coastline.

Tonight and Sunday...VFR with diminishing wind.

Sunday night...VFR to start with MVFR conditions expanding from
south to north towards daybreak. Chance of snow showers during
the overnight.

KBOS Terminal...High confidence.

KBDL Terminal...High confidence. Cannot rule out the potential
for a snow shower this evening.

Outlook /Monday through Thursday/...

Monday: Mainly VFR, with areas MVFR possible. Chance SHSN,
slight chance FZDZ.

Monday Night: Mainly VFR, with local MVFR possible. Slight
chance FZDZ.

Tuesday: Mainly VFR, with local MVFR possible. Windy with areas
gusts to 30 kt. Slight chance SHRA.

Tuesday Night: VFR. Windy with gusts to 30 kt. Slight chance
SHRA.

Wednesday: VFR. Windy with gusts to 35 kt.

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

Thursday: VFR. Breezy.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Sunday Night/...High confidence.

Tonight...W-NW gusts to 25-30 kt lingering into this evening
before diminishing after midnight. SCA all waters.

Sunday and Sunday night...Light NW winds with seas below SCA.

Outlook /Monday through Thursday/...

Monday: Winds less than 25 kt. Chance of snow showers, slight
chance of rain showers, slight chance of freezing drizzle.

Monday Night: Winds less than 25 kt. Slight chance of freezing
drizzle.

Tuesday: Moderate risk for Small Craft Advisory winds with
gusts up to 30 kt. Local rough seas. Slight chance of rain
showers.

Tuesday Night: Low risk for gale force winds with gusts up to
30 kt. Local rough seas. Slight chance of rain showers.

Wednesday: Low risk for gale force winds with gusts up to
35 kt. Areas of rough seas.

Wednesday Night: Moderate risk for Small Craft Advisory winds
with gusts up to 30 kt. Local rough seas.

Thursday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas locally approaching 5 ft.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 1 AM EST Sunday for ANZ231>234-251.
     Small Craft Advisory until 7 PM EST this evening for ANZ230-
     236.
     Small Craft Advisory until 3 AM EST Sunday for ANZ235-237-250.
     Small Craft Advisory until 8 AM EST Sunday for ANZ254>256.

&&

$$
SYNOPSIS...Frank/Dunten
NEAR TERM...Dunten
SHORT TERM...Dunten
LONG TERM...Frank
AVIATION...Frank/Dunten
MARINE...Frank/Dunten


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