Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 031732
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1232 PM EST Sat Dec 3 2016

.SYNOPSIS...

Low pressure over the maritimes will circulate a dry but chilly
airmass into New England today on blustery northwest winds. Chilly
and dry weather persist into Sunday. However, winds slacken as
high pressure builds into the area from the west. A few brief snow
or rain showers are possible Sunday night and Monday as a weak
trough moves across the region. High pressure returns Monday night
with mainly dry conditions into Tuesday. Low pressure off the mid
Atlantic coast may bring some mixed light rain and/or snow into
southern New England late Tuesday night into Wednesday night,
though timing and track remain uncertain. A polar front crosses
the region late next week resulting in a trend toward colder than
normal temperatures.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1230 pm update...no major changes to the forecast.

Continued cyclonic flow through which mid-level energy as seen in
the latest water vapor satellite is stretching through the tight
pressure gradient resulting in a local enhancement of the winds.
The boundary layer well-mixed up to H8, should see drier air and
faster winds mix down to the surface with the possibility of gusts
up around 35 mph at times. Will see a reinforcing shot of colder
air as well the passage of which will result in winds becoming
more N. Clouds still an issue over the N/W high terrain, downsloping
and clearing out over S/E portions of S New England. But with the
more N trajectory of the winds, going to be contending with ocean-
effect clouds and the slight chance of showery weather over the
Outer Cape.

Overall, a overall dry and seasonable day with breezy conditions
which will make it feel a few to several degrees colder.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SUNDAY/...

Tonight...

Cold air advection continues along with gusty northwest winds of
15 to 25 mph. However inland winds will drop off to less than 10
mph. Thus leaned toward the colder MOS guidance for low
temperatures...20s for most locations...low 30s for the immediate
coastline where winds will not decouple.

Some cold advection strato-cu from time to time but dry weather
will prevail. The only exception may be across the outer Cape as
cold air advection on NNW winds will result in ocean effect clouds
and snow showers. However hi res guid including the ARW and NMM
keep the bulk of the ocean effect snow showers offshore as
boundary layer winds may have enough westerly component...about
320 degs. Given this uncertainty will carry chance and slight
chance pops for snow showers across the outer Cape.

Sunday...

Heights begin to rise a bit so probably more sunshine than
today. However sunshine will be fairly ineffective given a cold
airmass over the area and less blyr mixing as subsidence
inversion lowers with approaching high pressure. Temps will be
about 5 degs cooler than today with highs only in the upper 30s to
lower 40s...mid 30s high terrain. These numbers are about 5 degs
colder than normal.

The good news these height rises will be accompanied by high pres
building over the region. Thus pgradient will weaken resulting in
winds not as gusty as today.

&&

.LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/...

Highlights...

* Temperatures running near to slightly below seasonal normals
  through midweek.

* Low pressure looks slowly move across the Ohio Valley and mid
  Atlantic states, which may bring some mixed rain and/or snow
  into the region Tuesday night into Wednesday night, but
  confidence remains low.

* A strong polar front approaches late next week, possibly bringing
  more unsettled conditions.

Sunday night through Monday...Moderate confidence.

A weak mid level short wave and associated surface reflection looks
to bring a band of scattered rain and/or snow showers across the
region during this timeframe. 00Z model suite in better agreement in
holding on to band of light QPF amounts as it crosses. Low
probability that there might be some light snow accumulations
/0.5 inches or less/ mainly across the higher inland terrain late
Sunday night into Monday morning. Precip should push offshore during
Monday afternoon. Have kept low CHC POPs in the forecast.

Monday night...Moderate confidence.

Dry conditions and mostly clear skies prevail Monday night with
surface high pressure centered over southern Quebec...and upper
level ridging...being the main influence on our weather.

Tuesday and Wednesday...Low confidence.

Models showing a bit better continuity with next approaching
system during this timeframe. High pres ridge pushes into Quebec,
with southern extent bringing E-NE winds. Some model timing issues
in place on how quickly the leading edge of the overrunning precip
pushes into the region. Seems the latest GFS is bringing precip
shield NE a bit faster than the GGEM and ECMWF.

Looks like best chance for light rain and/or snow will occur
Tuesday night and Wednesday as low pressure moves slowly up to mid
Atlantic coast, associated with H5 short wave moving NE in the SW
flow behind to exiting long wave ridge that crosses the region Tue
night.

Still uncertainty as to exact track of the mid Atlantic low
pressure, as well as moisture field to the W of the region with
the second low. Noting a rather strong cutoff H5 low S of Hudson
Bay, which looks to be digging a deep long wave trough across the
western Great Lakes and Mississippi valley. Also seeing arctic
airmass diving SE out of western Canada and Alaska late Wed/Wed
night.

Light precip could linger through Wed night, depending upon track
of the coastal low as well as developing system in the central
U.S.

Thursday and Friday...Low confidence.

Models continue to signal development of H5 long wave trough with
arctic airmass diving into the Plains states. Timing and track
differences remain on the 00Z model runs, along with how the
sensible weather evolves.

At this point, looks like the coastal low swings across the
region sometime Thu, with another front swinging out of the Ohio
Valley late Thu night or Fri. Again, timing in question with how
quickly the second front swings eastward. Have continued chance
POPs for this forecast.

&&

.AVIATION /18Z SATURDAY THROUGH THURSDAY/...

Forecaster Confidence Levels...

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

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

Remainder of today...
VFR. SCT-BKN low-end VFR cigs over N/W MA and CT high terrain as
well as across the Outer Cape. Low risk MVFR. NW winds gusting as
high as 35 kts with highest gusts over high terrain, coastline.

Tonight...
VFR. NW winds diminishing but initially blustery. Gusts up around
25 kts dampening. Cigs dissipating.

Sunday...
VFR. Mostly clear with light NW winds.

Sunday Night into Monday...
Mostly -SN with coastal -RA for the Monday morning push. Will see
conditions deteriorate briefly around 9-15z to IFR with -SN as
VSBY will most likely be impacted. Cigs mainly MVFR, IFR for the
high terrain. W winds around 5 to 10 kts. Improving VFR beginning
around 18z Monday.

Monday Night...
VFR. SKC. Light NW winds.

KBOS TAF...Gusty NW winds continuing around 25 to 30 kts.
Diminishing through the overnight period.

KBDL TAF...Gusty NW winds continuing around 25 to 30 kts.
Diminishing through the overnight period.

Outlook /Tuesday through Wednesday/...

Tuesday and Wednesday...Moderate confidence for overall trends,
lower on exact timing. Should be mainly VFR Tuesday morning. May
see MVFR CIGS/VSBYS move into central and western areas Tuesday
afternoon in mainly -RA, but may see mixed precipitation across
the interior. MVFR to local IFR CIGS/VSBYS possible Tue night into
Wed with chance of -RA and/or -SN.

&&

.MARINE...

Forecaster Confidence Levels.

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

Short Term /through Sunday/...

1230 pm update...No major changes. Forecast on track.

Today...

Expect W-NW winds gusting up to 25-30 kt. A few gusts to 35 kt
possible, but subgale winds will be observed most of the time.
Any ocean effect snow showers should remain well offshore.

Tonight...

NNW winds 20-25 kt. Given more northerly wind direction ocean
effect snow showers will track closer to the coast especially just
east of Cape Cod.

Sunday...

NNW winds 20-25 kt early but then diminishing as high pressure
builds over the area. Any ocean effect snow showers across eastern
MA waters early will diminish by afternoon.

Outlook /Sunday Night through Wednesday/...Moderate confidence.

Sunday night and Monday...Winds will remain below small craft
criteria. Seas may briefly linger at around 5 ft on the outer
waters E of Cape Cod
7 AM Update..., but should subside.

Monday night through Tuesday night...Winds and seas remain below
small craft criteria for most of the waters. NE winds shift to E
and increase, gusting to around 20 kt Tuesday night across the
southern outer waters.

Wednesday...E winds will gusts to around 20 kt, possibly up to 25
kt on the southern outer waters. Seas forecast to build to 5-6 ft
there as well.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...

CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 10 AM EST Sunday for ANZ230>237-250-
     251-254>256.

&&

$$

SYNOPSIS...Nocera/Sipprell/EVT
NEAR TERM...Nocera/EVT
SHORT TERM...Nocera
LONG TERM...EVT
AVIATION...Nocera/Sipprell/EVT
MARINE...Nocera/EVT


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