Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 031224

Area Forecast Discussion
National Weather Service Taunton MA
724 AM EST Sat Dec 3 2016

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.



7 AM Update...

Area of mid clouds moving across the region at 12Z tending to
break apart across central and eastern areas, while lingering
across the west. Noting thin bands of showers across central NY
state, but tending to dissipate as they shift SE. Only other area
of precipitation noted is across far northern NY into NW VT near
Lake Champlain. Mid level short wave working SE out of Hudson Bay
as seen on latest water vapor satellite imagery. With the general
W-NW wind flow in place at the surface and aloft, not much in the
way of moisture will work across the region. Have kept a mainly
dry forecast in place.

As winds shift to a more NW-N direction today, may see some ocean
effect clouds develop near or just E of outer Cape Cod. Could see
some lower clouds work in there off and on through the day.

Have updated near term forecast to bring conditions current.

Previous Discussion...

As the potent early morning H5 short wave exits eastward into the
Gulf of Maine, the main impacts for southern New England will be
a reinforcing surge of colder air on gusty northwest winds. This
will result in high temperatures about 5 degs cooler than
Friday...with highs today about 40-45...except upper 30s for the
high terrain. These temps are near normal however it will feel
colder given gusty NW winds of 20 to 30 mph. Dry weather prevails
today with cyclonic flow aloft and some lake effect influence
yielding some cloudiness from time to time.


330 am update...


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.


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.



* Temperatures running near to slightly below seasonal normals
  through mid week
* 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

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

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

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.


Forecaster Confidence Levels...

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

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


Mainly VFR. May see marginal MVFR CIGS across higher terrain at
times. May see brief sprinkles or flurries through mid morning,
then mainly dry conditions. W-NW winds gusting up to 30-35 kt
through the day, highest gusts over the higher terrain and Cape
Cod and the islands.


VFR and dry with gusty WNW winds up to 25 kt or so...strongest
winds across the high terrain and Cape Cod and islands.


VFR and dry along with diminishing NNW winds.

KBOS TAF...High confidence in TAF. Main impacts will be gusty WNW
winds today and tonight with gusts up to 30 kt at times.

KBDL TAF...High confidence in TAF. Main impacts will be gusty WNW
winds today and tonight with gusts up to 30 kt at times.

Outlook /Sunday Night through Wednesday/...

Sunday night and Monday...Moderate confidence. May see patchy
MVFR conditions in scattered -SHRA/-SHSN Sunday night through
midday Monday, then should be mainly VFR by Monday afternoon.

Monday night...Moderate confidence. VFR.

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.


Forecaster Confidence Levels.

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

Short Term /through Sunday/...

7 AM Update...


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.


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.


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, 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.


MARINE...Small Craft Advisory until 10 AM EST Sunday for ANZ230>237-250-


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