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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
1006 am EDT sun Oct 20 2019

Synopsis...

High pressure sliding east as clouds increase from the west. Remnants
of Nestor tracking S of New England will bring the possibility
of rain overnight. High pressure returns Monday. An approaching
cold front will bring an area of rain from midday Tuesday through
Tuesday night. High pressure returns Wednesday afternoon through
early Friday with seasonably mild temperatures and dry weather.
Scattered showers move across late Friday through Saturday as
another front approaches.

&&

Near term /until 6 PM this evening/...

10 am update...

Continuously monitoring the upcoming overnight rain threat that's
associated with the remnants of Nestor. Upstream, 12z okx sounding
highlighting plenty of dry air below h5, the coming rain shield
over PA that is hardly reaching the ground. How well this dry air
remains in place as upslope precedes a weak mid-level 500 mb-7 open
shortwave beneath the right-rear-quadrant of a 300 mb jet streak is
still up for interpretation. Stable heights, an isallobarically-
enforced wedge of dry air and high pressure from the southeast Canadian
Maritimes, there's going to be a north cutoff of outcomes. A North-Draw
along and around the 300k isentropic surface undergoing lift
beneath definitely some mid-level ascent ahead of a very weak
trof axis. Certainly should see some outcomes via radar. But
again, does it reach the ground. Still a large spread in forecast
solutions with a soaking to nothing struggling in handling The
Bumper-cars of airmasses.

Drawing memories of a similar setup a few weeks back, the North-Plains
cyclone ahead of which heights begin to rise as S-stream energy
sweeps east just S of New England, confident the S-coast will see
rain, and thinking perhaps as far north as the MA-Pike. Avoiding the
extremes, leaning towards the lower-end consensus of forecast
rainfall guidance. Thinking along the lines of near the 25th-
percentile. Looking as if the islands will see a decent rainfall
however further north it remains light with amounts around and less
than a tenth of an inch.

Sunshine and increasing clouds for now as remnants of Nestor
approach. Highs getting into the low 60s especially over east/southeast
interior Massachusetts with greater sunshine through today. Pleasant and
dry, great autumn weather.

&&

Short term /6 PM this evening through 6 PM Monday/...

Tonight...

Hi res guidance has begun to trend southward like the global models
regarding rain shield and wind field associated with remnants of once
Nestor. Greatest risk for rain tonight will be along the South Coast
including Cape Cod and the islands. Mainly dry weather prevails else-
where. Trended the forecast in this direction however if models
continue this farther south trend later forecasts may not offer much
if any rain to our South Coast with bulk of rain remaining offshore.

Clouds and possibly rain South Coast will result in a seasonably
cool night. Light east-northeast winds develop as remnants of circulation exit
the NC/Virginia coast.

Monday...

Low pressure tracks south of 40n/70w in the morning and then moves
southeast farther out to sea in response to short wave ridging
advecting across New England. Thus any morning clouds should give
way to at least partial sunshine if not abundant sunshine along with
seasonably warm conditions with highs 60-65. Very pleasant with
light winds.

&&

Long term /Monday night through Saturday/...

Highlights...

* spotty showers move across late Monday night into Tuesday
* cold front sweeps across, bringing an area of rain Tuesday
afternoon into early Wednesday
* high pressure brings dry, mild conditions late Wednesday into
early Friday
* another front approaches with scattered showers late Friday
through Saturday

Details...

Monday night...

As the remnants of Nestor spin S of Nantucket, the onshore flow
may allow enough low level moisture to allow some spotty
showers to develop mainly across eastern areas after midnight.
Looks like the best chance will be across Outer Cape cod and
Nantucket. Temps will fall back to the upper 30s across portions
of north central/northwest mass, ranging to the lower 50s along east coastal
areas.

Tuesday and Wednesday...

Low level moisture will remain high with the continued onshore
flow as low clouds develop during Tuesday. May see some spotty
drizzle through midday.

Deeper layer moisture approaches as the leftovers of Nestor
become absorbed by a steadily approaching cold front out of New York
state later Tuesday. Increasing pwats move in Tuesday night into
the pre-dawn hours Wed, up to 2-3 South Dakota above normal as the front
sweeps eastward overnight. May see some spotty heavy rainfall
across the east slopes of the Berkshires, with forecasted quantitative precipitation forecast
amounts from 0.5 to 0.75 inches during the overnight hours.

Most of the 00z model suite in pretty good agreement in
bringing the front across overnight, pushing off the East Coast by
mid morning or so on Wednesday.

Expect improving conditions from midday Wednesday Onward as
west winds may gust up to around 20-25 kt, highest along S
coastal areas. Temps will top off in the mid-upper 50s across
the higher inland terrain to the lower-mid 60s across the
coastal plain and lower CT valley.

Wednesday night through Saturday...

Large high pressure passes S of New England Wed night through
Thursday night with dry westerly winds in place. Temps will run
around 5 degrees above seasonal normals on Thursday.

Another front may approach during Friday, but timing and track
are in question due to model solution spread with the departure
of the front to the S. May see scattered showers move across
late Friday and Friday night, then another low may develop
across southeast U.S. And move up the coast Fri night into Sat. Lower
forecast confidence due to the timing and track issues during
this timeframe. Continued with chance pops from Fri afternoon into
Sat.

&&

Aviation /14z Sunday through Thursday/...

Forecaster confidence levels...

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

Short term /through Monday/...

14z update...

Today...high confidence.
VFR. Light winds. Increasing clouds lowering to low-end VFR over
southwest CT.

Tonight...moderate confidence.
Broken-overcast low-end VFR with MVFR over CT / Rhode Island / southeast MA, the
risk of IFR across the cape and islands, even perhaps the mid-CT
River Valley towards early Monday morning as cigs clear. An
increasing east/NE wind 10 to 15 kts along the coast, as high as 20
kts across the cape and islands with gusts as high as 30 kts that
heighten early morning Monday.

Monday...moderate confidence.
Low-end VFR - MVFR cigs eroding S/east through the day. A NE wind
persisting, MVFR broken-overcast cigs may linger across the cape and
islands much of the day. Winds diminishing throughout.

Kbos terminal...
high confidence in taf.

Kbdl terminal...
high confidence in taf.

Outlook /Monday night through Thursday/...moderate confidence.

Monday night: mainly VFR, with local IFR possible. Breezy.
Patchy br.

Tuesday: MVFR/IFR conditions possible. Breezy. Chance rain.

Tuesday night: MVFR/IFR conditions possible. Breezy. Rain likely,
chance shra, patchy br.

Wednesday: mainly VFR, with local MVFR possible. Breezy. Slight
chance rain showers.

Wednesday night through thursday: VFR. Breezy.

&&

Marine...

Forecaster confidence levels...

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

Short term /through Monday/...

10 am update (no major changes)...

Today...high confidence.
High pressure over New England this morning moves slowly off-
shore this afternoon. Thus light winds and flat seas along with
dry weather and good vsby.

Tonight...moderate confidence.
Surface low may track farther south.

Remnants from once Nestor exits the NC/Virginia coastline and moves
northeast to south of 40n/70w toward daybreak Monday. NE winds
increase but winds greater than 25 kt may track south of
Nantucket. Rain shield overspreads the southern waters with dry
weather likely across the northern Massachusetts waters.

Monday...high confidence.
Surface low south of 40n/70w moves southeast farther out to sea.
Thus NE winds diminish but some swells may linger. Any early
morning rain over southern waters gives way to dry weather and
good vsby.

Outlook /Monday night through Thursday/...moderate confidence.

Monday night: winds less than 25 kt. Areas of rough seas.
Slight chance of rain.

Tuesday: winds less than 25 kt. Areas of rough seas. Chance of
rain.

Tuesday night: winds less than 25 kt. Areas of rough seas.
Rain, chance of rain showers.

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

Wednesday night through thursday: winds less than 25 kt. Seas
up to 5 ft.

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

$$

Synopsis...nocera/evt
near term...nocera/sipprell/evt

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