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000
FXUS61 KBOX 232010
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
410 PM EDT Fri Sep 23 2016

.SYNOPSIS...
A cold front will cross the region this evening, bringing lower
temperatures. A band of rain showers is also expected behind this
front later this evening into tonight, but amounts will be light.
Cool and dry weather will follow this weekend into early next
week. A slow-moving low pressure and cold front could lead to
some showers late next week.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
Latest mesoanalysis continues to show a very unfavorable
environment for supporting thunderstorms across southern New
England. Abundant clouds, as well as a stout low level inversion,
from earlier today has limited our warm up. More sunshine
developing across southern New England this afternoon. But it may
be a case of too little, too late.

Looking upstream, lots of lower clouds behind a cold front across
southern VT and NH. That indicates more abundant moisture, and the
possibility of some showers. Short-term guidance, such as the
HRRR and RAP, continues to indicate a higher likelihood of at
least some lightly measuring showers. Will continue with a brief
period of chance PoPs this evening. Only moderate confidence
rainfall chances will actually be as high as suggested by the
guidance with few radar returns upstream, despite the run-to-run
consistency of the guidance.

Band of rain showers will continue to press from north to south with
band of mid level frontogenesis/moisture behind a cold front. Much
cooler air will continue to work into the region tonight and northeast
winds will be a bit gusty along the coast.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
Drier air will move in from the northwest, allowing for skies to
become mostly sunny during the morning. Mostly clear skies
continue through Saturday night.

Below normal temperatures during this time as well. If winds can
diminish enough, there is the remote possibility of some frost
across portions of the east slopes of the Berkshires Saturday
night, particularly in Franklin county. Will need to monitor this,
but think it is a low probability event at this time.


However, a fall-like
atmosphere will be in place with 850T between +3C and +5C. High
temps should still recover well into the 60s to near 70 given lots
of sunshine, but certainly be our first true taste of early fall.

&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
Highlights...
* Dry and cool weather continues through Monday with patchy
  frost possible for some locations Sunday night.
* Precipitation chances increase Monday night thru Wednesday
  night, with a return to seasonable temperatures.

Overview and model preferences...

Omega block over the Mississippi Valley continues to translate east
and gradually deamplify through the middle of the upcoming week.
The 23/12Z model suite begins to diverge around 12Z Monday, with the
ECMWF notably weaker, and thus more progressive, with its handling
of the closed low over the Great Lakes. We leaned toward the slower
and more amplified GFS solution, given the interaction of several
pieces of energy, as the ECMWF may be breaking down the block too
quickly. But confidence in the details is below average, and will
remain so, until the models better resolve competing shortwave
energy interacting with the closed low.

Details...

Sunday and Monday...
Northwest flow aloft will keep the region dry during this time frame,
as Canadian high pressure crests across the region by Monday morning.
Given the combo of a dry airmass in place, as well as a decoupled
boundary layer, we anticipate ideal radiational cooling conditions
to occur Sunday night. Thus, we went below guidance on temperatures,
which may bottom out in the low to mid 30s for portions of the
region.  In particular, the interior locations northwest of the Mass
Pike and I-495, as well as interior southeast Massachusetts, have
the potential for their first frost of the season. Otherwise, there
will be an increase in mid and high level cloudiness on Monday, as
a warm front approaches the region.

Monday night thru Wednesday... There is still uncertainty with the
timing of a cold front during this time frame, with the more
progressive ECMWF keying in on Tuesday  morning, while the GFS holds
off until Wednesday afternoon. We leaned more toward the GFS, and
focused PoPs in the Monday night to Wednesday morning period. We
also kept consistency with the previous forecast, with the greatest
chance of precip focused in the late Tuesday thru early Wednesday
time frame, when the deepest moisture and strongest dynamics
coincide. This system does not have much in the way of moisture to
work with, as Precipitable Water values only rise to 1.5 inches, so
rainfall will be generally light. We also cannot rule out a rumble
of thunder along the south coast Monday night into early Tuesday, as
some elevated instability traverses this area.

Thu and Fri...
Still some uncertainty regarding how quickly the upper low departs
the region. We maintained NIL to low PoPs, especially considering
the amount of moisture along the back side of this feature.

&&

.AVIATION /20Z FRIDAY THROUGH WEDNESDAY/...
Forecaster Confidence Levels.

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

Tonight...Moderate to high confidence. A period of MVFR CIGS in a
band of showers are likely behind a cold front. Northeast wind
gusts of 20 to 25 knots expected along the coast.

Saturday...High confidence. Mainly VFR. Any leftover MVFR Cigs,
and perhaps some patchy early morning fog in the typical
locations, will improve to VFR by mid morning.

Saturday night...High confidence. VFR.

KBOS TAF...Moderate confidence in TAF due to shower coverage. High
confidence in winds. Wind shift to the northeast with brief
gusts to 25 kt possible between 23/20Z and 24/06Z, along with a
period of MVFR CIGS and showers.

KBDL TAF...Moderate confidence in TAF due to shower coverage. High
confidence in winds.

Outlook /Sunday through Wednesday/...

Sun thru Mon...High confidence. Predominantly VFR. Northwest
winds may gust to 25 kt near shore on Sunday.

Mon night thru Wed...Moderate confidence.
Localized MVFR conditions possible in showers, mainly Tue night into
Wed, with uncertainty with regard to timing.  Otherwise VFR.

&&

.MARINE...
Forecaster Confidence Levels.

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

Tonight...High confidence. A strong cold front should result in a
period of northeast wind gusts up to 25 knots, and 3 to 6 foot
seas across our open waters, early this evening into the
overnight hours. Small craft headlines posted for all waters
except Narragansett Bay.

Saturday into Saturday night...High confidence. Leftover 25 kt
wind gusts diminish by mid morning as pressure gradient weakens.
However, small craft headlines will continue across our outer
waters into mid afternoon from leftover swell. These seas should
finally drop below small craft advisory thresholds by late
afternoon. Increasing north to northwest winds with a stronger
surge of colder air over the waters. Not confident there will be a
long period of sub advisory winds. So, will continue the small
craft advisory into Saturday night across the outer coastal
waters.

Outlook /Sunday through Wednesday/...

Sunday and Sunday night...High confidence.
Small craft advisory conditions prevail. Northwest wind gusts
around 25 knots Sunday, with seas 5 to 6 feet expected into
Sunday night.

Monday...
Conditions are expected to remain below Small Craft Advisory
criteria with high pressure building over the waters.

Monday night thru Wednesday...
An approaching storm system will lead to a period of southerly flow
over the waters during this time frame. Small Craft Advisory criteria
is possible during this period, however, the timing is uncertain.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 PM this evening to 8 AM EDT
     Saturday for ANZ231>235-237.
     Small Craft Advisory until 11 PM EDT this evening for ANZ230.
     Small Craft Advisory until 6 AM EDT Sunday for ANZ250.
     Small Craft Advisory until 8 AM EDT Saturday for ANZ251.
     Small Craft Advisory from 8 PM this evening to 6 AM EDT Sunday
     for ANZ254>256.

&&

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