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000
FXUS61 KBOX 200521
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
121 AM EDT Sun Aug 20 2017

.SYNOPSIS...
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A cold front will cross region overnight, followed by very warm
but less humid air on Sunday. High pressure brings dry and
seasonable weather Monday. It will be hot and humid Tuesday.
ahead of an approaching cold front, which will bring a chance of
showers and thunderstorms from late Tuesday afternoon into
early Wednesday afternoon. High pressure will bring dry and
cooler weather late in the week into next weekend.
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&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
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120 AM Update...

Showers were dissipating over western MA where airmass is more
stable and is a bit drier aloft than to our west. May still see
brief shower or sprinkle across western/central MA into
Merrimack valley through sunrise, otherwise dry weather is
expected overnight.
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&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
Sunday...

Spectacular late summer weather tomorrow with mid level mean trough
axis pushing offshore resulting in height rises across the area.
Warming temps aloft and flow becoming less cyclonic will yield less
diurnal clouds/more sunshine than today. Model soundings show a deep
boundary layer with drier air aloft mixing to the surface. This
combined with downslope WNW winds will result in dew pts falling
into the upper 50s. So despite temps climbing well into the MU80s to
near 90, lowering dew pts will make it somewhat tolerable. Given the
deep blyr and downsloping winds, increased temps a few degs warmer
than guid.

Sunday night...

Any diurnal clouds erode with sunset giving way to mostly clear
skies. This combined with high pres building into the area will
promote radiational cooling and temps falling into the upper 50s
outside of the urban areas. Used MOS temps to derive mins tomorrow
night.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Big Picture...

At upper levels, closed low pressure will be moving slowly
across Canada, from west of James Bay Tuesday to eastern Quebec
by Saturday. The trough axis extending southward from the low
will remain to our west until Saturday. The cold pool of air
will arrive over our region around Thursday and remain in place
into next weekend.

At the surface, high pressure will pass southeast of the region
Monday. A cold front moves through Wednesday. Then strong high
pressure builds over the Great Lakes states, with its influence
extending eastward into New England.

Details...

Monday...

High pressure off the DelMarVa coast will provide sunny skies
for southern New England, warm temperatures, and relatively
light southwest winds. Forecasting highs in the mid to upper
80s over most of the interior, with comfortable humidity.

Tuesday...

Southwest breezes behind departing high pressure and well in
advance of an approaching cold front will usher in very warm and
more humid air. With 925 mb temperatures of about 25C, am
expecting highs to reach the upper 80s and lower 90s. Winds
could gust to 15-20 mph during the afternoon. Dewpoints will be
rising to near 70 by late afternoon and heat indices will be in
90-94 range, just shy of heat advisory criteria. With the
afternoon heating will come a chance of a few showers and
thunderstorms late in the day, especially in western MA and
northern CT, closer to the approaching front.

Tuesday night-Wednesday...

A cold front will slowly work its way across the region.
Showers and thunderstorm probabilities increase to 40-60 percent
Tuesday night and mainly in eastern sections on Wednesday. The
ECMWF is slower with the frontal progression than the GFS. Wind
fields are somewhat strong, with 35-40 kts at 925 mb and 850 mb
Tuesday night. Cannot rule out a few strong thunderstorms
Tuesday night, even though they would not be occurring during
the maximum heating. Skies will be clearing from west to east
during the day. West to northwest winds could gust to 20 to 25
mph behind the front. Highs mainly 80 to 85 Wednesday.

Thursday-Saturday...

Strong high pressure building into the Great Lakes states will
exert its influence across New England. At the same time, an
upper level trough will be moving overhead, along with it
associated cold pool with 500 mb temperatures reaching -18C
Thursday and continuing into Saturday. It also will be cooler in
the lower levels. Forecasting high temperatures in the 70s each
day, possibly near 80 in spots. It should be dry for the most
part, with scattered diurnal clouds.

&&

.AVIATION /05Z SUNDAY THROUGH THURSDAY/...
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Forecaster Confidence Levels...

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

Short Term /through Monday/...

06z TAF Update...High confidence.

LIFR in fog will persist around ACK through sunrise, before
rapid improvement to VFR. Otherwise VFR today and tonight. Winds
shift to W/NW and gust to 15-20kt at times from late morning
into afternoon, especially across interior, before diminishing
late in the day.

VFR Monday with W/SW winds, gusting to 15-20kt near South Coast
in the afternoon. Low chance of a sea breeze along East Coast
for a few hours early in afternoon, but right now we are more
confident in no sea breeze occurring.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday...High confidence. VFR. Only
exception will be IFR in patchy late night fog, mainly Monday
night, then improving to VFR by mid morning Tuesday.

Tuesday night-Wednesday...Moderate confidence. VFR Tuesday but
areas of MVFR cigs/vsbys in showers and thunderstorms late
Tuesday afternoon in western sections, across the region Tuesday
night and Wednesday morning, and in eastern sections Wednesday
afternoon. IFR cigs possible in early morning fog/low clouds
especially in areas that have had rain. Clearing in west half
Wed. afternoon. Clear Wed night.

Thursday... High confidence. VFR.
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&&

.MARINE...
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Forecaster Confidence Levels...

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

Short Term /through Monday/...Moderate confidence.

Tonight...

Onshore winds across the eastern MA waters veer to the SW after
sunset and then west toward daybreak. Patchy low clouds/fog will
also move offshore with the wind shift this evening and especially
toward daybreak. Elsewhere, SSW winds continue with areas of fog
possibly redeveloping along the south coast. Chance of a shower
late tonight, especially along the north coast.

Sunday...

Modest WNW winds will promote dry weather and good vsby.

Sunday night...

WNW winds become very light as high pres build in from the west. Dry
weather and good vsby prevail.

Outlook /Monday Night through Thursday/...

Monday through Tuesday...High confidence.

High pressure south of the waters. Southwest winds remain less
than 15 knots Monday but may increase to near 20 knots late
Tuesday. Seas less than 3 ft, but increasing to 3 to 4 ft over
the outer waters late Tuesday.

Tuesday night-Wednesday...Moderate confidence.

A cold front approaches from the Great Lakes, crossing the
waters late Wednesday or Wednesday night. Southwest winds
increase with gusts 20 to 25 knots during Wednesday. Winds shift
to the northwest Wednesday night. Seas build Tuesday night and
Wednesday reaching 5 to 6 ft on the outer waters. The southwest
flow may also nudge those higher seas into RI Sound as well. A
Small Craft Advisory may be needed on some of the waters during
this time.

Thursday... High confidence.

As high pressure to our north and west builds over the northeast
states, winds will turn more to the north and northeast. But
they will be diminishing to less than 10-15 knots and seas will
subside to 3 ft or less.
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&&

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

&&

$$
SYNOPSIS...Nocera/GAF
NEAR TERM...JWD
SHORT TERM...Nocera
LONG TERM...GAF
AVIATION...JWD
MARINE...Nocera/GAF