Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 080632

Area Forecast Discussion
National Weather Service Boston/Norton MA
132 AM EST Fri Dec 8 2023

High pressure maintains dry weather through Saturday with
temperatures rising to above normal levels. A strong frontal
system has the potential to bring a period of heavy rain,
strong southerly winds and coastal flooding along the south
coast late Sunday into early Monday. Turning drier by Monday
afternoon with a brief shot of colder air for Monday night, but
temperatures look to rebound back closer to seasonable levels
by next Tuesday and Wednesday.


Satellite data showed more clouds in place across the western
half of southern New England early this morning. This will put
the brakes on radiational cooling there. Guidance continued to
struggle with the extent of these clouds, so relied more on
extrapolating observed satellite data for sky cover through

Weak high pressure remains in control of our weather, providing
another dry day. However, a warm front approaching from the SW
will result in warmer temperatures as well as a period of
clouds. Expecting high temperatures to be near to slightly below
normal today.


Not much change tonight into Saturday. Warm front should
struggle to move completely north of our region by Saturday
evening. However, there should be enough of a surge of warm air
to result in near to slightly above normal temperatures, despite
partly to mostly cloudy skies. Dry weather continues through


Key Points...

* Quiet, dry, and milder the first half of Sunday.

* A strong storm system will bring widespread rain, strong
  (potentially damaging) winds, and the possibility of coastal
  flooding on the south coast.

* Quiet and colder Tuesday through Thursday

We`ll see a very deep trough cross the region, bringing
unsettled weather to the region Sunday into Monday which will be
discussed in further detail below. Beyond that more zonal mid
level flow moves in with broad surface high pressure at the
surface for Tuesday into at least Wednesday leading to dry,
quiet, and colder weather for mid week as highs settle back in
the 40s.

The main focus in the extended forecast period is the late
Sunday into Monday period as a strong frontal system and neutral
to slightly negatively tilted trough move out of the Ohio
Valley and cross New England Sunday night. The anomalous nature
of several parameters including moisture (PWAT) and wind spell
potential for a concerning event on a few fronts.

As for the rainfall potential, this system has abundant
moisture with PWATs exceeding 3 standard deviations from normal
for December. This, combined with the very strong dynamics (a
low level jet ranging from 50 kts to as much as 80+kts over the
outer Cape) will yield rainfall amounts from 1 to 2+ inches
between Sunday and Monday afternoon. The highest amounts will be
over the interior (western MA/CT) where forcing will be
enhanced by orographics as well as from the slightly negatively
tilt of the mid level trough and divergence aloft thanks to
placement beneath the right rear quadrant of a 145 kt low level
jet. This is also where there is a tight gradient from core of
the LLJ to the slower winds to the north which will enhance low
level convergence. Ensembles depict a 20-30% chance of seeing 3+
inches of rain here. Further east we may see localized maxima
thanks to some elevated instability in the warm sector leading
to scattered convection. The progressive nature of the system
will help keep flooding issues from being a big concern (save
for urban/poor drainage flooding) but some rises on rivers are
expected, and the MMEFS depicts a 30% chance of minor flooding
at points on the CT River; something to watch.

As for winds, given the aforementioned anomalous low level jet
and expected temperature inversion near the surface over
southeast MA it will be a matter of just how much of that wind
can mix down to the surface. One thing that could help mix down
the stronger gusts would be any convective elements that may
develop. To be sure, it will be windy regardless, but as for the
45+ mph potential that will be confined primarily to RI and
southeast MA. Ensemble guidance depicts a 50-80% chance of 45+
mph gusts over this region; generally thinking 45-60 mph gusts
are the best bet right now but things will change as we get into
the higher resolution guidance.

Finally, the peak of the southerly winds looks to be during the
early morning hours of Monday. Even though places like
Narragansett Bay won`t have an astronomically high tide at the
time, if the peak of the wind/surge coincides with high tide
(6:20am in Providence) it could spell some coastal flooding is
possible. It will all come down to exact timing which we won`t
be able to nail down until much closer to the event.


Forecast Confidence Levels:

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

Today...High confidence.

VFR for most with generally light N to NW winds becoming S to SW
this afternoon. Areas MVFR towards the Berkshires this morning.

Tonight and Saturday...Moderate confidence.

Mainly VFR ceilings for most. Main uncertainty remained the
possibility and extent of MVFR ceilings towards the CT River
Valley tonight, which may briefly spread east towards daybreak
Saturday. Light southerly winds expected through this period.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday Night through Tuesday/...

Saturday Night: VFR.

Sunday: Mainly VFR, with areas IFR possible. Strong winds with
local gusts up to 40 kt. Chance RA, patchy BR.

Sunday Night: Mainly IFR, with areas MVFR possible. Strong
winds with gusts up to 50 kt. RA, isolated TSRA, patchy BR.

Monday: Mainly VFR, with local IFR possible. Strong winds with
gusts up to 50 kt. RA, patchy BR.

Monday Night: VFR. Windy with gusts up to 35 kt.

Tuesday: VFR. Breezy.


Forecaster Confidence Levels:

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

High Confidence.

Expecting relatively light winds and seas through Saturday. A
warm front should move across the southern coastal waters
Saturday, but remain west of the eastern coastal waters through

Outlook /Saturday Night through Tuesday/...

Saturday Night: Winds less than 25 kt.

Sunday: Low risk for gale force winds with gusts up to 35 kt.
Seas locally approaching 5 ft. Chance of rain. Local visibility
1 to 3 nm.

Sunday Night: Low risk for storm force winds with gusts up to
50 kt. Rough seas up to 14 ft. Rain, isolated thunderstorms,
patchy fog. Visibility 1 to 3 nm.

Monday: Low risk for storm force winds with gusts up to 50 kt.
Rough seas up to 15 ft. Rain, patchy fog. Areas of visibility
1 to 3 nm.

Monday Night: Low risk for gale force winds with gusts up to
35 kt. Rough seas up to 13 ft.

Tuesday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Areas of rough seas.




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