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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
205 am EDT Mon Sep 16 2019

Synopsis...
high pressure will bring an extended period of dry weather into
next weekend, other than perhaps brief spot showers Monday. The
high will initially be accompanied by unseasonably cool weather
Tuesday into Thursday morning. A gradual warmup is expected
with temperatures possibly rebounding into the 80s Friday
through Sunday.

&&

Near term /until 6 am this morning/...

145 am update...

High, thin clouds continue to spread across the region, mainly
from the Route 2 area southward, as seen on latest GOES-east
nighttime microphysics rgb satellite imagery. Noting a band of
broken clouds from 5k-7kft, lying from near Boston and the
South Shore wwd into north Rhode Island and NE CT through the high thin
clouds as well as latest surface observations.

Still noting spotty showers pushing across central and southern
New York state into north central PA on latest NE regional 88d satellite
imagery along a weak, nearly stationary front that extends into
S VT/NH. However, they were tending to dissipate as they tried
to cross the Hudson River into the Berkshires and Litchfield
Hills, though a lower overcast lies just across the border into
far west mass. Some of those lower clouds may try to push erd into
the east slopes of the Berkshires through daybreak.

With light/variable or calm winds across the region with the
weak pressure gradient, some spots could see some fog develop,
especially across the CT valley and possibly the normally
susceptible areas of interior east mass after 07z or so.

Temps should bottom out mainly in the 50s, coolest across the
mid and upper CT valley and interior east mass, ranging to around
60 near the coast.

&&

Short term /6 am this morning through 6 am Tuesday/...

Today...

A weak wave of low pressure across the southern Great Lakes
early this morning will slide southeastward through the day.
This will take the better forcing/moisture to the southwest of
our region. So while we probably will see a period of some
cloudiness, at least across our CT/Rhode Island and southeast Massachusetts expect little if
any rain other than a few spot showers. Greatest risk will be
across northern CT and near the South Coast, but regardless dry
weather should dominate in this region too.

High temperatures on Monday will probably still reach the lower
to middle 70s in many locales given at least some partial
sunshine.

Tonight...

High pressure in Quebec will force a cold front south of the
region this evening. While dry weather should continue tonight,
it will turn cooler on northerly winds. Low temperatures by
daybreak Tuesday should mainly be in the middle 40s to the lower
50s.

&&

Long term /Tuesday through Sunday/...
highlights...

* high pressure brings dry weather Tuesday through Sunday
* cooler than normal Tue-Thu, warming Friday into the weekend

Details...

Precipitation...

An very dry forecast in the extended, painting the picture for a
very pleasant week/weekend in southern New England. Building
surface high pressure with a persistent mid level ridge set up
to our immediate west will keep southern New England under a dry
north/northwest flow through at least Saturday. No significant weather to
speak of.

Temperatures...

A very fall-like feel will arrive beginning Tuesday and lingering
through at least Thursday. This as north/NE flow sets up around the
sfc-850 mb high ushering in cold Canadian air. 850 mb temps drop to
the 2-5c range by mid week, with the coldest period likely being
Wed and Thursday morning. Highs Tuesday and Wednesday won't
break out of the 60s, compared to average highs of 70-75. Steady
warming is expected thereafter. Thursday some 70s return, then
we get well into the 70s Friday and back into the 80s for the
weekend. Yes, the return of Summer-like temperatures is possible
this weekend into early next week as the ridge moves overhead.
Before that, though, we'll also be dealing with chilly low
temperatures. Given the dry, calm, clear nights we'll get some
decent radiational cooling, with lows bottoming out Thursday
morning in the 40s before rebounding to the 50s by the weekend.

Tropical Storm Humberto...

We continue to expect little to no impact from Tropical Storm
Humberto as model guidance shows the surface high helping to
deflect it out to sea well to our south and east. As mentioned
previously, the only real impact we may see would be increased
swells for the Massachusetts/Rhode Island waters, bringing rough surf and strong rip
currents around Friday/Saturday.

&&

Aviation /06z Monday through Friday/...
forecaster confidence levels...

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

Short term /through tonight/...high confidence.

0545z update...

Through 12z...mid and high clouds are increasing but VFR
conditions continue. Light winds.

Today...VFR conditions dominate despite some mid level
cloudiness. Low risk of brief MVFR conditions south of the Massachusetts
Turnpike with a spot shower or two possible. Rather light winds.

Tonight...VFR. North winds of 5 to 10 knots.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Tuesday night through Friday/...high confidence.

Tuesday: VFR. Breezy.

Tuesday night: VFR.

Wednesday: VFR. Breezy.

Wednesday night through friday: VFR.

&&

Marine...
forecaster confidence levels...

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

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

Overnight and Monday...weak pressure gradient will allow winds
and seas to remain well below Small Craft Advisory thresholds.

Monday night...a cold front will cross the waters Monday
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. We can not rule out brief Small Craft Advisory conditions, but threat
is too marginal to hoist any headlines at this point.

Outlook /Tuesday night through Friday/...moderate confidence.

Winds less than 25 kt. Areas of seas approaching 5 ft.

&&

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

&&

$$
Synopsis...Frank/bw

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