Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 240743
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
343 AM EDT Mon Jun 24 2019

.SYNOPSIS...

Dry and warm weather continues today, except not as warm along the
immediate coast given onshore sea breezes. An approaching warm front
will bring a period of widespread showers and perhaps a few embedded
thunderstorms Tuesday. Summer-like warmth is expected Wednesday through
Friday with a few showers and thunderstorms possible at times,
but dry weather should dominate. A better chance of showers and
thunderstorms may arrive sometime this weekend along with a
trend to somewhat cooler weather.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

330 am update...

Today ...

Another beautiful day on tap for the region with deep layer ridge
remaining west of New England and providing anticyclonic mid level
flow and associated subsidence/dry air across the region. Thus
expecting abundant sunshine today filtered by occasional mid/high
clouds this afternoon and perhaps even some high based SCU/CU per
BUFKIT time sections. Nevertheless, a gorgeous day with mostly sunny
conditions and highs this afternoon in the low to mid 80s. The
exception will be at and near the coast with high pressure overhead
promoting afternoon seabreezes and yielding highs in the 70s.
Comfortable humidity once again today with model PWATs less than an
inch and surface dew pts in the upper 40s and lower 50s, although
rising to 55-60 along the coast once seabreezes advect slightly
higher maritime airmass into the coastal plain.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM TUESDAY/...

330 AM update ...

Tonight ...

Mostly clear at sunset combined with light winds and a dry airmass
will allow temps to fall noticeably during the evening. However
increasing clouds shortly thereafter as warm advection pattern
approaches from the west. Thus temps will level off second half of
the night. In fact deep layer moisture and mid level lift overspread
much of CT and western-central MA after 06z. However low level dry
air will take sometime to erode so most of the night will remain dry
with just a chance of rain entering western CT/MA including the
Greater Hartford/Springfield areas toward 12z Tue.

Not as cool as tonight given increasing clouds and dew pts inching
upward.

Tuesday ...

Warm frontal wave approaches from the west with rain likely across
western portions of MA/CT at 12z. Deep layer moisture and lift
overspread the remainder of the area from west to east yielding
widespread showers especially from late morning into the afternoon.
Modest low level southerly jet of 40 kt combined with some
instability above this layer (negative showalters) and PWATs surging
up to 2.0 inches should support a few embedded heavy downpours along
with the risk for a few elevated thunderstorms.

Later shifts will have to monitor potential for heavy rainfall. Some
of the guidance suggesting 1+ rainfall with HREF match mean up to
1.5-2.0 inches with a focus across CT into RI and southeast MA.
Given the convective nature too early to pinpoint location or
magnitude of qpf. Thus stay tuned to later forecasts.

Much cooler Tue given clouds, showers and onshore southeast winds.
Although dew pts rising thru the 60s will provide increasing humid
conditions.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

Highlights...

* Steady showers exit the coastal plain early Tue eve with just a
  few lingering spot showers Tue night along with fog/patchy drizzle

* Summer-like warmth Wed/Thu/Fri with a few showers/t-storms possible
  but expect dry weather to dominate the majority of the period

* Trending somewhat cooler this weekend with perhaps an increased
  risk for showers and thunderstorms at times

Details...

Tuesday night...

Deep layer moisture and forcing exits the coastal plain early
Tuesday evening, bringing an end to the steady showers.  The rest of
the night should feature just a few spot showers with lingering low
level moisture. The bigger concern will be for areas of fog
developing with light winds and dewpoints > 60.  Some patchy drizzle
is also possible, but again the steady showers will have exited the
coastal plain early in the evening.  Given dewpoints over 60, low
temps should only drop into the lower to middle 60s.

Wednesday through Friday...

EPS/GEFS guidance continues to indicate strong upper level ridging
building across the central and southeast states.  Our region will
be on the southern edge of the westerlies, but ensembles continue to
indicate height fields/850T anomalies that are a bit above normal.
While we are not looking at any extreme heat, above normal
temperatures are a good bet.  Highs should be well up into the 80s
to near 90 in many locales, at least away from any localized cooling
marine influences near the immediate coast at times.

Overall, we expect dry weather to dominate in the Wed through Fri
time frame given the lack of deep moisture/synoptic scale forcing.
However, we should be able to generate some instability and with
decent westerly flow aloft a few showers/t-storms are possible at
times.  So while the majority of this period will feature dry
weather, will need some low pops to account for this risk.

This Weekend...

Upper level trough over eastern Canada amplifies southward into part
of the northeast this weekend.  The result will be trend towards
somewhat cooler weather and an increased risk for some showers and
thunderstorms at times.  Still plenty of uncertainty in this time
range, but something will need to watch in the coming days.

&&

.AVIATION /08Z MONDAY THROUGH FRIDAY/...
Forecaster Confidence Levels...

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

Short Term /through Tuesday/...High confidence.

0540z update ...

Today ... VFR and dry weather continue. Light WNW before sunrise
become light and variable inland later this morning into the
afternoon but onshore winds along the coast as seabreezes
develop.

Tonight ... VFR to start but MVFR/IFR arrive 06z-09z across CT
and western-central MA, possibly into RI. Low risk of showers
entering western MA/CT toward 12z. Otherwise remainder of the
region stays dry.

Tuesday ... VFR possible early across eastern MA, otherwise
MVFR/IFR with spotty LIFR from late morning into the afternoon
accompanied by widespread showers with embedded thunder and
heavy rain. Southeast winds.

KBOS Terminal...High confidence in TAF. Seabreeze develops early
14z-15z from the northeast and slowly turns to the E-SE toward
00z.

KBDL Terminal...High confidence in TAF.

Outlook /Tuesday Night through Friday/...Moderate confidence.

Tuesday Night: Mainly VFR-MVFR, with local IFR possible. Breezy.
Areas FG, slight chance SHRA.

Wednesday through Thursday: Mainly VFR. Slight chance SHRA, isolated
TSRA.

Thursday 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.

Today ...

Very pleasant boating weather with high pressure over PA and NY this
morning then cresting over New England this afternoon, providing
light winds and seabreezes near shore. Dry weather and good vsby as
well.

Tonight ...

High pressure slides offshore yielding southeast winds across the
MA/RI waters. Dry weather prevails but some lower vsbys in fog may
sneak into the RI waters toward daybreak Tue.

Tuesday ...

Warm front moves across the waters with widespread showers and areas
of fog with reduced vsby at times. A few thunderstorms with heavy
downpours are possible.

Outlook /Tuesday Night through Friday/...Moderate confidence.

Tuesday Night: Winds less than 25 kt. Areas of seas approaching
5 ft. Chance of rain showers, areas fog. Visibility 1 to 3 nm.

Wednesday: Winds less than 25 kt. Seas locally approaching
5 ft. Areas fog. Local visibility 1 to 3 nm.

Wednesday Night through Thursday Night: Winds less than 25 kt.
Slight chance of rain showers, isolated thunderstorms.

Friday: Winds less than 25 kt.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$
SYNOPSIS...Nocera/Frank
NEAR TERM...Nocera
SHORT TERM...Nocera
LONG TERM...Frank
AVIATION...Nocera/Frank
MARINE...Nocera/Frank


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