Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 230223
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1023 PM EDT SUN MAY 22 2016

.SYNOPSIS...
Dry into the first half of Monday, before a second area of low
pressure moves up the coast and ushers in wet weather through
Tuesday. A significant warmup will occur Wednesday, continuing
into next weekend. Scattered showers or thunderstorms are possible
from Thursday into next weekend, especially over western sections.

&&

.NEAR TERM /UNTIL 6 AM MONDAY MORNING/...

Between weather systems as upper low pressure winds up near the
Carolina coast. Expect dry weather overnight with mostly clear
skies. Dew points in the mid 40s to low 50s, so min temps will be
in a similar range.

&&

.SHORT TERM /6 AM MONDAY MORNING THROUGH MONDAY NIGHT/...
Monday...

A return of wet weather. Coastal low off the Mid-Atlantic gets wound
up and pulled back, occluding towards the N and W beneath the mid to
upper level low. Will see an increase in wet weather and clouds as a
result of several factors.

The first per a trowaling confluence of conveyor belts as mid-level
vortex energy parent to the mid to upper level low pushes N. Parent
forcing on the increase along with an isallobaric NE wind results in
high-end chance to likely PoPs late.

The second per vortex energy stretched and inverted N of the low
maintaining low level confluence across Upstate NY and PA E into the
CT River Valley. Cooler air aloft yielding steeper lapse rates in an
environment of favorable lift, with any diurnal forcing especially
with sunshine we would likely see some shower activity emerge. Focus
especially along the high terrain with orographic influences upon
convergent flow.

The likely window of partial clearing more likely N and W just prior
to increasing cloud and PoP chances late should allow highs to warm
into the low to mid 70s. Cooler E and SE with increasing NE onshore
flow. Will follow closely to ensemble probabilities with regards
to PoP chances in such a chaotic pattern that has been poorly
handled by a majority of the forecast guidance.

Monday Night...

Surface low continues to back and occlude beneath the cutoff mid to
upper level low pulling N and across S New England in response. In
its mature to dying phase conveyor belt motions undergo strong
forcing across much of S New England within the comma head of the
low itself. This prior to drier air wrapping into and cutting off
the system.

Likely PoPs warranted early, perhaps diminishing into morning. Will
need to monitor SE New England for the possibility of an elevated
convective setup. Weak instability but strong shear, convective
indicies exceeding respective thresholds, can not rule out a rumble
of thunder for SE communities but have low confidence with regards
to a severe threat with any convection.

Abundance of clouds and moisture with a continued E/NE flow, looking
at lows in the low to mid 50s.

&&

.LONG TERM /TUESDAY THROUGH SUNDAY/...
Highlights...

 * Good chance of showers Tuesday
 * Significantly warmer Wednesday into next weekend
 * Scattered showers and thunderstorms Thursday into next weekend,
   especially over western sections.

Overview and Model Preferences...

Very good agreement in the latest guidance suite in moving a
persistent upper low toward the Maritimes by late Wednesday
afternoon. Strong ridging over the north Atlantic edges west over
the southeast USA late this week. This will mean more summer-like
conditions late this week into next weekend. With the increasing
heat and humidity, also expecting the possibility for diurnal
showers and thunderstorms, each day.

Subtle, but significant, differences in the details Friday into
next weekend. The predictability of these details is rather low,
so will favor a consensus approach, for now.

Details...

Tuesday...

Core of the upper level cold pool moves over southern New England.
Still differences in the specific low tracks among the latest
models, so confidence is not high on this particular aspect, yet.
Guidance does agree on a low pressure passing close enough to
southern New England where we would need at least a chance for
some showers in the forecast.

We will need to keep an eye on the possibility of some
thunderstorms, too. While the cold pool aloft will mean an
unstable atmosphere, the northeast onshore flow should limit the
available energy to put into thunderstorm updrafts.

Expecting below normal temperatures due to abundant clouds and
scattered showers.

Wednesday...

Brief ridge of high pressure to our south takes over, leading to
downslope air flow, drier conditions, and more summer-like
temperatures away from the coast. There could be seabreezes, but
it appears the synoptic flow could be just strong enough to
prevent lower temperatures along parts of the MA east coast. Cape
Cod and the islands, as well as Cape Ann, however, will likely
remain as cool as the south coast of New England, where southwest
winds should prevail.

Thursday through Sunday...

This still appears to be a prolonged period of summer-like heat
and humidity, especially away from the coasts. The questions to
be answered during this portion of the forecast are: where will a
frontal boundary be between Thursday and Friday, and how quickly
will it move? A scenario can be seen where we wind up on the cold
side Friday, which would mean lower temperatures and a greater
risk for showers.

Diurnal showers, and perhaps some thunderstorms, are expected
through most of this period. The position of this front will have
a large impact on chances, and is one of the more uncertain
aspects of this forecast. Will keep a chance for showers in the
forecast until this critical detail can be better worked out.

&&

.AVIATION /02Z 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/...

Overnight...Moderate Confidence.

VFR with light wind. Clear skies and light winds along with temps
near saturation may support local IFR cigs/vsbys in patchy fog
after midnight.

Monday...Moderate Confidence.

Low-end VFR cigs with MVFR across E/SE coastal terminals. Will
heighten the risk of IFR to moderate keeping it confined to SE
coastal terminals. -SHRA developing late, focus along the S coast
as well as the N/W interior out into the CT River Valley. NE flow
prevailing with gusts up to 20 kts especially over the E/SE coast.

Monday Night...Moderate Confidence.

-RA likely for all terminals. Deteriorating conditions into the
evening hours and prevailing overnight. Mix of MVFR down to LIFR
with NE winds prevailing, gusts upwards of 20 kts especially across
the E/SE coastal terminals. A final note, there is a low risk of
TSRA for SE coastal terminals.

KBOS TAF...Pulling out MVFR and keeping cigs VFR with the low-end
of the spectrum SCT per webcams shortly before 18z. Not much issue
in thinking with landing on the 4`s if that be the case with NE
winds prevailing, gusts up to 15 kts.

KBDL TAF...Becoming SCT and dry and such trends should continue
into the overnight hours. N winds with gusts limited to 15 kts.
Will see a return of low cigs and wet weather late Monday with a
continued downward trend into Monday night.

Outlook /Tuesday through Friday/...

Tuesday...Moderate Confidence.

Scattered showers will continue across the area with NE flow. An
isolated TSRA is also possible. This also suggests low clouds.
Therefore, periods of MVFR/IFR are likely, but it`s possible that
occasional VFR will occur, especially across the interior.

Wednesday...High Confidence. Mainly VFR.

Thursday...Moderate Confidence. Mainly VFR. Scattered MVFR in
scattered showers and thunderstorms, mainly west of KLWM-KORH-KIJD.

Friday...Moderate Confidence. Mainly VFR. Scattered MVFR in
scattered showers and thunderstorms.

&&

.MARINE...
Forecaster Confidence Levels.

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

Tonight...High confidence.

Coastal low lifts into SE Canada behind which NE winds diminish.
Seas remain 5 to 9 feet so small craft advisories continue on the
outer waters.

Monday into Monday Night...Moderate confidence.

Second coastal low moves up the coast through the day with impacts
towards late. Into evening will see increasing areal coverage of
rain along with NE winds. Restrictions to visibility with the wet
weather along with gusts up to 20 kts. Seas maintain 5 to 7 feet.
Small craft advisories continue.

Outlook /Tuesday through Friday/...

Tuesday...Moderate Confidence.

Secondary low lingers with subsequent wind and S swell. Seas may
reach 7 to 8 feet south of Nantucket. Small craft advisories may
need to continue for some waters.

Wednesday into Friday...High Confidence.

High pressure briefly builds over the waters. Mainly quiet
boating weather is expected with winds and seas below Small Craft
Advisory levels.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 2 PM EDT Monday for ANZ231-251.
     Small Craft Advisory until 2 AM EDT Monday for ANZ235-237.
     Small Craft Advisory until 8 AM EDT Tuesday for ANZ250-254-255.
     Small Craft Advisory until 8 AM EDT Monday for ANZ256.

&&

$$
SYNOPSIS...Belk/Sipprell
NEAR TERM...WTB/Belk/Sipprell
SHORT TERM...Sipprell
LONG TERM...Belk
AVIATION...Belk/Sipprell
MARINE...Belk/Sipprell



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