Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 060914
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
414 AM EST Tue Dec 6 2016

.SYNOPSIS...
Low pressure off the mid Atlantic coast may bring some mixed light
rain and/or snow into Southern New England tonight into early
Wednesday with any accumulations generally an inch or less. A
cold front crosses the region late Thursday or Thursday evening,
followed by another cold front Friday, which will usher in blustery
and unseasonably cold conditions Friday night into Saturday. Low
pressure may bring some snow or rain Sunday night into Monday.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
Patchy black ice will continue to be a concern on untreated
surfaces through about 8 AM this morning. This is covered in a
Special Weather Statement.

Otherwise, today should be dry with a fair amount of unshine given
surface high pressure moving across the region underneath an upper
level ridge. High clouds will likely begin to spread west to east by
late afternoon. Temperatures today should be near the climatological
norms.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM WEDNESDAY/...
Tonight...Two chunks of short wave energy influence our sensible
weather tonight. A short wave trough in the northern stream
passes to our NW while another short wave in the southern stream
passes s of us. The southern stream short wave trough instigates
surface cyclogenesis along the mid Atlantic coast, but this
system remains rather flat and will likely slide to the east well
south of our area. There could be some warm advection resulting
in overunning clouds/precipitation with the northern system, but
associated dyanmics stay well NW of the forecast area. Thus,
we`re anticipating light precipitation for our area with the aid
of a low level trough between the two systems. We may not even
measure along portions of the coastal plain. Have gone with
chance POPs NE half of area and low likely POPs across the SW
half of area.

Ptype is also not a sure bet. Thermal profiles look cold enough to
support precipitation mainly in the form of snow along and north
of the Mass Pike and whatever precipitation falls likely
mixed rain/snow across northern CT, northern RI, and along the
I-95 corridor between Providence and Boston. If the
precipitation intensity should be heavy enough, then we could see
the thermal profile cooling close to the wet bulb and perhaps
more snow than rain across northern CT. In addition, an easterly
low level flow could result in some modest enhancement over the
eastern slopes of the Berkshires and perhaps to a lesser degree
along the Worcester hills and higher terrain of NE CT and far NW
RI. In the end, however, we are expecting only a coating to an
inch of snow where the precipitation ends up being mainly snow.

By daybreak the deep moisture is gone with possibly just some lingering
areas of drizzle under the trapped low level moisture. There is a
slight chance of some light freezing drizzle across northern MA
around daybreak Wed but confidence is not very high.

Expect temperatures to remain fairly steady in the lower 30s
across much of the interior and in the mid to upper 30s across
the SE coastal plain.

Wednesday...Measurable precipitation should be over by
around daybreak with possibly just some lingering drizzle for a
while inthe morning. Areas of light freezing drizzle is a
possibility for a time across NW MA. Low clouds may persist
through most of the day with no mechanism to dissipate or move
them out. Partial clearing is possible late in the afternoon but
not a guarantee. Anticipate high temperatures to be in the lower
to mid 40s across most of the forecast area on Wednesday.


&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Highlights...

* Blustery, and unseasonably cold Friday night into Saturday
* Some snow/rain possible Sunday night into Monday

Thursday...A mid level longwave trough will pass by Thursday,
along with a surface cold front. There appears to be enough
moisture to result in abundant clouds, but perhaps not enough to
generate widespread rain and snow showers. Still looking like
steady west winds, which are generally not favorable for either
lake-effect or ocean-effect showers across southern New England.
As such, will keep this portion of the forecast mainly dry.
Seasonable temperatures expected.

Friday and Saturday...
This will be the most noticeable change during this portion of the
forecast. Unseasonably cold air should arrive Friday afternoon,
and really take hold Friday night into Saturday. Expecting
temperatures Friday night to be about 10 degrees below normal,
with high temperatures Saturday generally below our normal low
temperature, some 10-15 degrees below normal. Dry weather should
prevail across southern New England.

Gusty NW winds both days will result in wind chills in the single
digits and teens Friday night into Saturday. Saturday night lows
remain tricky, and will ultimately depend on extent of radiational
cooling. There remains potential for temperatures to be
significantly lower than the current forecast if it ends up clear
with winds decoupling.

Sunday into Monday...

Low confidence in the details of this portion of the forecast.
Significant spread in the track and timing of a low pressure
moving through the Great Lakes. GFS develops a stronger mid level
shortwave, while the ECMWF retains a nearly zonal flow over the
USA. Canadian model develops a weaker, more progressive,
shortwave than the GFS. Will maintain a chance of some rain and
snow across southern New England. However, these details are
likely to change over the next several days.

&&

.AVIATION /09Z TUESDAY THROUGH SATURDAY/...
Forecaster Confidence Levels...

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

Today...High confidence. After patchy fog burns off, VFR
conditions should prevail with just some high cloudiness
increasing late in the afternoon. Tonight...Moderate confidence.
Increasing cloudiness and MVFR ceiling and visibilities likely
across western half of the area with light snow or light mixed
rain and snow. MVFR ceiling may spread to the eastern half of the
area late tonight. Wednesday...Moderate confidence. MVFR ceiling
may persist through Wednesday morning and then gradually lifting
to VFR levels during the afternoon.

KBOS TAF...High confidence today and moderate confidence tonight.
VFR through this evening possibly lowering to a MVFR ceiling late
tonight into Wednesday morning.

KBDL TAF...High confidence today with VFR conditions. Moderate
confidence tonight into Wednesday morning. MVFR ceilings and
visibilities in light snow likely after 03z tonight. MVFR ceiling
and visibilities in fog may linger into a portion of Wednesday
morning.

Outlook /Wednesday Night through Saturday/...

Thursday...Moderate confidence. Mainly VFR cigs. Areas of MVFR
possible across the interior with a few snow/rain showers.

Friday and Saturday...Moderate confidence. Mainly VFR cigs.
Localized MVFR in isolated snow showers far interior MA Fri.

&&

.MARINE...
Forecaster Confidence Levels.

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

Short Term /through Wednesday/...

Confidence...High

At 4 AM, winds were still gusting to near 30 knots across the outer
east coastal waters but just starting to slacken elsewhere. Winds
should diminish gradually this morning and plan to let the Small
Craft Advisories expire later this morning as scheduled from the
prior forecast. Light winds are anticipated this afternoon through
Wednesday across this office`s coastal waters.

Outlook /Wednesday Night through Saturday/...

Wednesday night through Thursday...High confidence. Light winds
and seas.

Thursday Night...High confidence. Increasing WNW winds, with gusts
up to 30 kt possible. Small Craft Advisories may be needed for
most waters.

Friday into Saturday...High confidence. NW gusts to 30 kt likely.
There is a moderate risk for some gale force gusts, too. Winds
gradually diminishing Saturday. However, rough seas will take
longer to subside across the outer coastal waters.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST this morning for
     ANZ231>235-237-251.
     Small Craft Advisory until 10 AM EST this morning for ANZ250-
     254>256.

&&

$$
SYNOPSIS...Belk/Thompson
NEAR TERM...Thompson
SHORT TERM...Thompson
LONG TERM...Belk
AVIATION...Belk/Thompson
MARINE...Belk/Thompson



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