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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
1050 PM EDT sun Sep 15 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 Monday morning/...

1030 PM update...

Band of mid level clouds crossed the region through this evening
as they tended to dissipate as they moved offshore. Otherwise,
mostly clear skies with patchy high thin clouds crossing the
region as seen on latest GOES-east nighttime microphysics
satellite imagery and 02z observations. However, some broken
clouds from 050-060 from north of kore to kaqw.

A thin band of showers extending from near ksyr to kalb, with
10sm -ra reported at kalb at 02z. Somewhat drier airmass across
the border into west mass so should be dry, but can not rule out a
few sprinkles moving across through around midnight or so.

Previous forecast in rather good shape, but did refresh to bring
conditions current.

Previous discussion...

Noting an increase in mid and high clouds as expected, with some
very light showers which should dissipate as they move east into
southern New England. Expect low temperatures mainly in the 50s by daybreak
Monday. Winds will be rather light too, so a pleasant night of
weather is on tap for the region.

&&

Short term /6 am Monday morning through Monday night/...

Monday...

A weak wave of low pressure across the southern Great Lakes
early Mon 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.

Monday night...

High pressure in Quebec will force a cold front south of the
region Monday evening. While dry weather should continue Monday
night 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 /03z Monday through Friday/...
forecaster confidence levels...

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

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

02z update...

Overnight...mid and high clouds are increasing but VFR
conditions continue. Light winds.

Monday...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.

Monday night...VFR. North winds of 5 to 10 knots.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Tuesday 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 Monday night/...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 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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