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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
334 PM EDT Mon Sep 16 2019

Synopsis...

High pressure will continue to bring an extended period of dry
weather right through the weekend. The high will initially be
accompanied by rather cool temperatures Tuesday night into Thursday
morning. A warmup occurs thereafter with unseasonably warm
afternoons expected by the weekend as highs may reach into the 80s.

&&

Near term /until 6 am Tuesday/...

Satellite continues to show not much displacement in the deck of
mid-high clouds over CT/coastal Rhode Island this afternoon. Short wave
energy continues to move through yielding a few scattered light
rain showers across CT in proximity to the deepest moisture,
with pwats >1.25" in southern CT and <1" in northern CT. Dry and
sunny elsewhere; temperatures have topped out in the low 70s
ahead of a few days of cooler temps. Tonight a reinforcing cold
front drops through bringing cooler and drier air south.
Dewpoints in the 40s sink as far south as the South Coast by
sunrise. Clear skies and light winds will allow for decent
radiational cooling, into the 40s inland...50s along the coast.

&&

Short term /6 am Tuesday through 6 am Wednesday/...

Pleasant, fall-like day on tap for Tuesday. Under the influence of a
building surface high pressure, with dry northwest flow at the mid
levels downstream of an amplified ridge over the Great Lakes region
we will be dry will plenty of sun. The cooling temperature
trend also continues, dropping below normal for mid September as
low/mid level flow becomes north then NE around the high. This
Ushers in cold Canadian air...2-5c at 850mb by early Wednesday!
At the surface we can expect low temps in the mid to upper 40s.

One thing to watch given the anomolously cold NE flow over our
still relatively warm ocean waters will be the introduction of some
ocean affect clouds late tues and overnight, maybe even some
light rain/drizzle. The column is very dry above 800mb but given
the substatial temp differential and low level moisture we may
squeeze out some light precip over northern and eastern Massachusetts
overnight; certainly nothing substantial or widespread

&&

Long term /Tuesday night through Monday/...

Highlights...

* extended period of dry weather continues through the weekend
* cool Wed/Wed night with moderating temps Thu and especially Fri
* unseasonably warm afternoon temps this weekend through Mon
* high surf/dangerous rip currents Fri into the weekend

Details...

Amplifying trough over the Canadian Maritimes will allow for a shot
of cool air Wed into early Thu am. North to northeast low level
flow will probably generate a period of clouds and perhaps even a
brief sprinkle or two Wed am. The main story though will be the
cool temperatures with highs mainly in the 60s Wed, perhaps
approaching 70 in the lower CT River Valley. The coolest highs on
Thu will be found on the eastern Massachusetts coast, where highs will struggle
to get past the lower 60s with the onshore flow.

Large high pressure in control will allow for rather cool temps Wed
night into early Thu am. Lows should be well down into the 40s with
perhaps some middle to upper 30s in the normally coolest outlying
locations. This may lead to some patchy frost in a few of these
spots, but even if that occurs it should not be widespread.

Upper level ridging over the Southern Plains begins to push
northeastward Thu into Fri allowing for moderating temperatures
especially by Fri. The ridge will then flatten a bit by the weekend
into Mon. This will allow more of a west southwest flow aloft and
even warmer temperatures to overspread the region by the weekend
into next Monday. A good shot we see high temperatures reach into
the 80s for at least a couple of those days. These readings are
generally 10 to 15 degrees above normal.

The extended period of dry weather will continue through the weekend
with nothing more than perhaps a sprinkle or two Wed am with large
surface high pressure in control.

Meanwhile, Hurricane Humberto currently well east of the Florida
coast will lift northeast, passing well east of our region by the
weekend. The only impact will be from swell resulting in high
surf/dangerous rip currents Fri and into the weekend. This is a
concern though for beachgoers especially given it will be occurring
with unseasonably warm temperatures.

&&

Aviation /20z Monday through Saturday/...
forecaster confidence levels...

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

Short term /through Tuesday night/...high confidence.

18z update...

This afternoon...VFR conditions. Mid and high clouds mainly
across CT, western MA, coastal Rhode Island this afternoon, diminishing
with time. Low chance for vcsh across north central/NE CT through
mid afternoon. North-northwest winds at 5-10 kt.

Tonight...VFR. Light north/northwest winds.

Tuesday and Tuesday night...VFR. Light north winds becoming NE.
Tuesday night toward early Wed may see some low end VFR cigs
from ocean effect clouds.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Wednesday through Saturday/...high confidence.

Wednesday through thursday: VFR. Breezy.

Thursday night: VFR.

Friday: VFR. Breezy.

Friday night: VFR.

Saturday: VFR. Breezy.

&&

Marine...
forecaster confidence levels...

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

Short term /through Tuesday night/...high confidence.

Tonight...a cold front will cross the waters this evening.
Decent mixing in the cool air advection pattern should yield a
period of northerly lower 20 knot wind gusts and 2 to 4 foot
seas.

Tuesday...N/NE winds. Seas 2-3 ft.

Tuesday night...light NE winds. Seas increasing 3-5 ft in outer
southern waters by early Wednesday morning.

Outlook /Wednesday through Saturday/...moderate confidence.

Wednesday through Wednesday night: low risk for Small Craft
Advisory winds with gusts up to 25 kt. Areas of rough seas.

Thursday through Thursday night: winds less than 25 kt. Local
rough seas.

Friday through Friday night: winds less than 25 kt. Rough seas
up to 10 ft.

Saturday: winds less than 25 kt. Rough seas up to 8 ft.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

$$
Synopsis...nocera/evt
near term...nocera/bw

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