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Area forecast discussion
National Weather Service Taunton Massachusetts
1202 PM EDT Wed Apr 26 2017

Synopsis...
low pressure will slowly track northeastward today, bringing
areas of rain, drizzle and fog. Then low clouds, drizzle and
fog are expected to linger tonight into Thursday especially
along the coast. Very mild to warm afternoons should return
Friday and Saturday, with a low risk for a few
showers/thunderstorms. Much cooler weather follows Sunday,
especially on the coast. Another cold front will likely bring
more showers to the region sometime Monday into Tuesday.

&&

Near term /until 6 PM this evening/...
weakening surface low was centered east of the New Jersey
coastline, heading slowly northeast. Warm front had lifted into
southeast MA, noted by a wind shift to the southeast, surface
dew points 55 to 60, and gusts of 25 to 35 mph.

Have updated forecast to reflect the warmer and more humid
conditions south of the front, with some higher wind gusts for
today. Otherwise across southern New England, patchy light rain
and areas of drizzle and fog are expected to continue thru this
afternoon. Continuing to moinitor reduced visibilities in fog,
visbility has lowered to 1/2 mile or less in some portions of
southeast MA/RI.

Early morning discussion for today...

Stacked surface low pressure system near the mid-Atlantic will move
towards southern New England today. Continuous southerly flow aloft
will continue to pump moisture into the region through the day.
Appears that surface warm front will try to move in, or may just
stall across the area. This will result in difference in
temperatures. For now continued with a blend in the guidance.

The main bulk of precip will lift this morning. However, still some
weak lift and with a very saturated moisture profile, anticipate on
and off showers late this morning and into the afternoon hours.

Increasing dewpoints across the South Coast could lead to patchy fog
development. Low confidence on how low vsbys will go, but something
to watch through the day.

&&

Short term /6 PM this evening through 6 am Thursday/...
Wednesday night...

Stacked low pressure system will begin to move south and east of the
region. 850 mb becomes more of a open wave resulting in a more
weaken system.

Upper levels appear to begin to dry out as the low begins to move,
however, at the surface and mid-levels, the profile is quite
saturated. Anticipate a soupy mess with low clouds and fog. Will
have to watch for vsbys dropping below a quarter of a mile which
would result in a dense fog advisory. Confidence is low at this
time, but something to watch.

Continuous easterly flow overnight combined with some weak lift will
result in areas of drizzle especially across eastern locations.

&&

Long term /Thursday through Tuesday/...
highlights...

* low clouds/spotty drizzle Thursday with cooler temps on coast
* mild to warm afternoons Fri/Sat with a low risk for a few
thunderstorms
* backdoor cold front brings much lower temperatures by Sunday
* period of showers, which may be briefly heavy, sometime Mon/Tue

Details...

Thursday...

Still dealing with a persistent mid level low near Nantucket
Thursday morning, while the surface low pressure is slightly
farther northeast. This will mean light onshore flow with lots
of low level moisture. Expecting cloudy skies with areas of
drizzle and fog, particularly across eastern Massachusetts. As noted by the
previous forecaster, MOS guidance is likely a little too high
with Max temperatures Thursday. Used the lower consensus of raw
model 2 meter temperatures for Max temperatures.

Friday and Saturday...this will be a tricky portion of the
forecast. An approaching cold front should become parallel to
the mid level flow, stalling somewhere just west of our region.
This should mean a persistent southwest flow, and much higher
temperatures than the past couple of days. Expecting Max
temperatures in the 70s degrees away from the south coastal
areas on both days.

However, these higher temperatures will combine with decent mid
level lapse rates to produce a low risk for thunderstorms. Right
now, Friday appears to have the greater risk of these two days,
as mid level dry air may be in place for Saturday. This could
all change should the stalled front shift closer to southern New
England.

Saturday night and Sunday...

A strong high pressure moves over eastern Canada, dominating
the blocking high pressure to our southeast. This push from the
northwest should be enough to drive the stalled front just to
our south, resulting in much lower temperatures, on the order of
15-20 degrees lower Sunday afternoon.

Monday and Tuesday...

A stalled front to our south should return as a warm front
sometime Monday into Tuesday as a low pressure moves from WI
into southeast Canada. The timing is still uncertain, as a
strong high pressure should be over Labrador. Should this high
linger longer than currently forecast, then the precipitation
timing will be also off. Still looking like another prolonged
window for periodic showers. Rainfall could be moderate to heavy
at times.

&&

Aviation /16z Wednesday through Sunday/...
forecaster confidence levels...

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

Short term /through tonight/...

Today...moderate confidence. Mainly IFR cigs, with local MVFR
cigs, continue with areas of -ra/-dz and patchy fog, especially
across the eastern half of southern New England. Reduced visibilities
likely, down to IFR/LIFR in spots. May see areas of LIFR ceilings
across the higher inland terrain and along the coast. Southeast winds
gusting up to around 25 kt across Cape Cod and the islands. Low level wind shear
impacts for the cape and islands during this morning.

Tonight...moderate confidence. MVFR-IFR conditions continue in areas
of fog and drizzle. A few showers are possible.

Kbos taf...high confidence in taf, moderate confidence in timing.

Kbdl taf...high confidence in taf, moderate confidence in timing.

Outlook /Thursday through Sunday/...

Thursday...moderate to high confidence. IFR to even LIFR
conditions likely into the morning along with some fog, drizzle
and a spot shower. Lower conditions most likely on the coast.
Conditions may improve to mainly MVFR by late Thu morning and
afternoon.

Thursday night and Friday...moderate confidence. MVFR/IFR
conditions likely in areas of low clouds and fog patches into
early Friday morning. Improvement to VFR likely by Friday
afternoon, with the low risk for a few showers and perhaps a
thunderstorm.

Saturday and Sunday...moderate confidence. VFR conditions.

&&

Marine...
forecaster confidence levels...

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

Short term /through tonight/...high confidence.

Gale Warning issued for the southeast coastal waters thru 4 PM,
including Nantucket Sound, Vineyard Sound and Buzzards Bay, and
the adjacent outer coastal waters. This portion of the coastal
waters is southeast of a warm front, allowing for some mixing
with the stronger winds aloft. Those stronger winds aloft are
expected to weaken later this afternoon, which will allow
surface gusts to lower.

For the remainder of the waters, small craft advisories are in
effect expect for Boston Harbor and Narragansett Bay. Seas will
remain above 5 feet with winds gusts near 20-25 kts into the
afternoon. As a coastal low begins to move eastward, winds gusts
will begin to subside and seas will relax. Small craft
advisories will still be needed for ocean waters, but overall
trend will be improvement. Visibility restrictions at times
across the waters this afternoon and tonight in locally dense
fog.

Outlook /Thursday through Sunday/...moderate confidence.

Winds are not expected to be be a concern through this portion
of the forecast, generally remaining less than 20 kt. The main
issue will be how long it takes for lingering swell from the
persistent low pressure near the waters to diminish. Small craft
advisories are likely to be needed across the outer coastal
waters.

In addition, areas of drizzle, fog or rain will lead to some
visibility restrictions on the coastal waters into Friday.

&&

Tides/coastal flooding...
* isolated minor coastal flooding impacts during astronomically
high tides through tonight along the east and south coasts

We are entering a Spring tide cycle with high tides that are
astronomically high. This combined with an anticipated storm surge
of around 1 foot may set the stage for isolated pockets of minor
coastal flooding along both south and east coasts around the time of
high tide this morning, and again tonight. Went ahead an issued
a new coastal flood statement for potential splashover. There
is also the combination of runoff from heavy rain and elevated
water levels near high tide this morning, which could exacerbate
drainage of fresh water in some coastal urban areas, and near
the mouths of streams and small rivers.

We will need to continue to monitor The Tides through at least
Wednesday night as there is not a significant offshore flow or
pressure rises to help evacuate a lingering surge. The astronomical
high tides remain very elevated through the end of the week.

Due to the breadth of the fetch, we may encounter enough wave action
with lengthening periods on top of an elevated tide to cause pockets
of erosion tonight through tonight along the Martha's Vineyard South
Coast, Nantucket south and east coasts, and the Outer Cape ocean
side from Truro to Chatham.

Boston high tides (flood stage at Boston 12.5 feet)...

11.47 feet / Tuesday 11:20 PM
11.15 feet / Wednesday 11:50 am
11.92 feet / Thursday 12:07 am

Providence high tides (flood stage at Providence 7 feet)...

5.98 feet / Tuesday 8:11 PM
5.53 feet / Wednesday 8:41 am
6.21 feet / Wednesday 9:00 PM

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Gale Warning until 4 PM EDT this afternoon for anz232>234-254-
255.
Small Craft Advisory until 8 PM EDT this evening for anz231.
Small Craft Advisory until 9 am EDT Thursday for anz235-237-
250-251-256.

&&

$$
Synopsis...Belk/dunten
near term...Belk/dunten/nmb

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