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000
FXUS61 KBOX 221359
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
959 AM EDT Thu Jun 22 2017

.SYNOPSIS...
High pressure in control today. Warm and humid air follows for
the remainder of the week into the weekend along with the threat
of heavy rain associated with the remnants of Cindy. The cold
front will stall across New England Saturday before moving offshore
Saturday night. Seasonably warm and less humid conditions Sunday
will be followed by cooler and somewhat unsettled weather for
early next week.

&&

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

1000 AM update...

Ongoing forecast remains on track for today as skies remains
mainly clear. Some cirrus will sneak through but should have
little impact on the region. Biggest issue today is the ongoing
seabreeze potential.

Previous Discussion...
SKC across SNE this morning. Pleasant summer day on tap with
sunshine, seasonably warm temps and comfortable humidity. Some
of the hi-res guidance indicating a seabreeze may develop along
the immediate east coast this afternoon. If it does come onshore
it will be confined to the immediate coastline.

Highs upper 70s to low 80s given mixing up around H85 where
temperatures range around +12C. The deep mixing allows for
surface dewpoints to drop around the low to mid 50s, some places
in the upper 40s. Few to scattered low clouds prior to
increasing high clouds towards evening as sub-tropical air
begins to ascend across the region. Expect 60 degree surface
dewpoints slip back N tonight.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH FRIDAY NIGHT/...
Tonight...

Remaining mild, becoming humid, as the chance of showers increase.
Continued ascent of sub-tropical moisture across the region with
accompanying elevated instability and higher K-indices, though
stronger low-level convergence and deep layer forcing is tied
more closely with the deep layer trough digging S out of Canada
into the Great Lakes Region. Subsequently, despite lift and column
saturation, the better chances of wet-weather are more likely N/W.
Expecting scattered light outcomes with the possible risk of
thunder. Continued S flow, surface dewpoints continue to rise
closing in on 70. Across the cooler ocean waters, more than
likely low clouds if not fog and visibility issues for SE New
England. Lows in the mid to upper 60s.

Friday...

Warm, muggy day with the chance of showers and thunderstorms. Sub-
tropical air continuing to surge from the SW pushing precipitable
waters above 2 inches as remnants of Cindy are stretched N. This
ahead of cyclonic flow tightening as mid-level energy continues to
push into the Great Lakes Region. Falling heights along with low-
level convergent forcing pushing into S New England, presents a
favorable environment in which partial clearing is expected, more
over the interior NE CONUS, for shower and thunderstorm development.
Low clouds along with visibility issues associated with fog / mist
are expected to sock in SE New England beneath the remnants of a dry
conveyor belt that had wrapped into Cindy. Lapse rates conditionally
unstable, more moist adiabatic contributing to thin-tall CAPE in an
environment of weak shear. Given the sub-tropical airmass in a broad
region of low-level convergent forcing and destabilizing boundary
layer, expecting mainly heavy rainers. Freezing levels up around 15
kft with precipitable waters in excess of 2 inches, efficient warm-
rain processes forecast with collision / coalescence. So with any
thunder will go with a mention of heavy rain. Higher chance PoPs
away from the S/E as highs warm well into the 80s. Wherever the
boundary layer mixes out it`ll likely be breezy from the SW with
gusts up to 25 mph.

Friday night...

Wet, muggy, mild. An anomalous setup attributable to the remnants of
Cindy. Roughly a +4-5 standard deviation (SD) of H85 moisture flux
and +3 SD of precipitable waters which exceed record highs recorded
at Chatham MA which average around 2 inches but are forecast around
2.25 inches. Will need to closely monitor any focusing mechanisms
which can put the squeeze on the atmosphere and possibly yield a
predecessor rainfall event.

Noting increasing low-level winds per tightening pressure gradient
ahead of mid-level troughing across the Great Lakes, convergently
focused in and around the S-shoreline of S New England ahead of a
sweeping cool front. Tightening baroclinic zone. Indications of
height falls within the mid-levels associated with weak troughing
signatures contributing to the convergence of sub-tropical air.
This as earlier daytime convection will likely shift S/E ahead of
said cool front. This in combination with tropical energy and some
diffluent motions aloft, can`t rule out a potential predecessor
rainfall event. Difficult to nail down at this time as to exactly
where but feel there is a risk to S New England around the Saturday
AM timeframe.

Looking at chance to likely PoPs for possible widespread rain with
embedded heavier showers and thunderstorms. Heavy rain threat per
efficient warm-rain processes still exists and will continue to
mention. Again, focus of heavy rain remains uncertain with respect
to potential flooding threats.

Surface dewpoints well into the 70s, a muggy and humid airmass for
certain, off the cooler ocean waters especially to the S/E, likely
dealing with foggy conditions overnight into the morning hours.
Could see visibility down to a quarter mile or less at times.

&&

.LONG TERM /SATURDAY THROUGH WEDNESDAY/...
Highlights...

* Sct showers and isold t-storms Sat, mainly south of the Pike
* Seasonably warm and less humid Sunday
* Cooler with showers possible at times early next week

Overview...

Longwave trof over the Gt Lakes will be the main feature in the
extended period. Polar jet will be in the vicinity of New Eng with a
series of weak shortwaves moving through the flow as the trof
gradually moves into New Eng early next week. This will bring a
somewhat unsettled pattern into the middle of next week with
cooler temps trending near or below normal.

Details...

Saturday...

Cold front expected to stall across SNE with tropical PWAT plume
exceeding 2" and high theta-e air remaining across southern half of
the region. Shortwave assocd with the remnants of Cindy tracks near
or south of New Eng and will likely bring a period of showers and
isold t-storms with brief downpours, especially south of the Pike. A
few showers may even extend into northern MA in the morning but
trend should be for improving conditions here in the afternoon with
developing sunshine.

Temps are tricky south of the Pike where clouds and showers may hold
temps down. We undercut guidance here with highs mostly in the 70s
to near 80 but low to mid 80s NE MA. Remaining rather humid south of
the Pike with dewpoints well into the 60s to near 70, but expect
dewpoints dropping into the 50s across northern and western MA in
the afternoon. Drier air will eventually make its way to the coast
Sat night with clearing skies.

Sunday...

The column is considerably drier Sunday so expect sunshine mixing
with diurnal clouds. Mainly dry conditions but mid level shortwave
tracking to the north and west may bring a brief showers to NW MA.
Seasonable temps in the upper 70s and lower 80s with low humidity as
dewpoints will be in the 50s.

Monday into Wednesday...

Gt Lakes trof will gradually move east into New Eng as a series of
shortwaves move through with mid level temps cooling through the
period. 500 mb temps -16 to -20C. This will result in an unsettled
pattern with showers or even an isold t-storm possible at times, but
low confidence on timing. Temps trending cooler to near or a bit
below seasonable normals.

&&

.AVIATION /14Z THURSDAY THROUGH MONDAY/...
Forecaster Confidence Levels...

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

Short Term /through Friday Night/...

Today...
VFR. Light winds gradually veering S. Sea-breezes possible along
the immediate E-coast. FEW-SCT CIGs around 6 kft. Increasing
high clouds from the W towards sunset.

Tonight...
CIGs becoming SCT to BKN lowering towards 4-6 kft with SHRA moving
in, the better chance of which will be across N/W CT and MA with
a low risk TSRA. Increasing S winds with the threat of MVFR VSBYs
along the S coast.

Friday...
SCT to BKN low-end VFR CIGs, more OVC across SE New England, as
S/SW winds increasing 10 to 15 kts sustained with gusts up to 25
kts. Increasing areal coverage of SHRA/TSRA with embedded threats
of +RA. TEMPO MVFR/IFR VSBYs with any RA/+RA while likely MVFR/IFR
VSBYs will plague the S-coast towards evening.

Friday night...
BKN to OVC MVFR/IFR CIGs with areas of IFR/LIFR FG towards SE New
England terminals. SHRA/TSRA continue with embedded threats of +RA.
There is also the low risk of LLWS impacts across the Cape and
Islands.

KBOS Terminal...Sea-breeze may develop this afternoon but
confidence not high. It could remain just offshore. VFR for the
entire TAF period. Increasing CIGs during the evening hours,
lowering into Friday morning.

KBDL Terminal...High confidence. VFR throughout.

Outlook /Saturday through Monday/...

Saturday...Moderate confidence.
MVFR and localized IFR in sct showers and isold t-storms, especially
south of the Pike with improving conditions, mainly VFR north of the
Pike.

Sunday...High confidence. Mainly VFR.

Monday...High confidence.
Mainly VFR cigs with a few showers possible in the interior.

&&

.MARINE...
Forecaster Confidence Levels...

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

Short Term /through Friday Night/...

High pressure today. Light winds veering though the day becoming
S overnight, increasing into Friday with sustained winds 10 to
15 kts and gusts up to 25 kts. This will push seas 5 to 6 feet
and require SMALL CRAFT ADVISORIES. With a cold front sweeping
down from the N as the remnants of TS Cindy advect N from the S,
will likely see the return of mist / fog conditions resulting
in low visibility down to a quarter mile or less at times.

Outlook /Saturday through Monday/...

Saturday...Moderate confidence.
Some gusty W/SW winds early Sat, possibly near SCA thresholds should
diminish in the afternoon. Seas up to 5-6 ft over the south coastal
waters.

Sunday and Monday...High confidence.
Winds should generally remain below small craft advisory thresholds
through the period. Lingering 5 ft seas over the south coastal
waters will subside Sun night.

&&

.TIDES/COASTAL FLOODING...
Astronomical tides are rather high this weekend during the night time
cycles. Boston has a 12.4 ft high tide around midnight Sat night and
12.2 ft just after midnight Sun night. Fortunately, offshore winds
are forecast with minimal or no surge so do not anticipate any
issues.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory from 8 PM Friday to 8 AM EDT Saturday for
     ANZ232>235-237.
     Small Craft Advisory from 2 PM Friday to 8 AM EDT Saturday for
     ANZ250-254>256.

&&

$$
SYNOPSIS...KJC/Sipprell
NEAR TERM...Dunten/Sipprell
SHORT TERM...Sipprell
LONG TERM...KJC/Sipprell
AVIATION...KJC/Sipprell
MARINE...KJC/Sipprell
TIDES/COASTAL FLOODING...staff

NWS BOX Office Area Forecast Discussion