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Area forecast discussion 
National Weather Service Taunton Massachusetts
1008 am EDT Monday Apr 27 2015

Synopsis...

Unsettled weather and below normal temperatures will continue into
Tuesday. Weak high pressure will briefly visit the area during
midweek...with temperatures near or slightly above normal. Below
normal temperatures and unsettled weather return Thursday night into
Friday...with improvements for this weekend.

&&

Near term /until 6 PM this evening/...

10 am update...

Some light shower activity will continue into this afternoon as an
elongated trough and attendant stretched middle-level energy rearward
of the nearly-stacked low southeast of Newfoundland sweep across S New
England. Main focus is towards evening as the low backbuilds into
the Gulf of Maine. Accompanying Stout middle-level impulse and upper-
level jet streak will invoke strong forcing along a backdoor cold
front. Have high confidence in hrrr trends as we go into evening.
Likely to high categorical probability of precipitation mainly east of the CT-River Valley.
Punch of colder air S/SW as winds turn blustery out of the N/NE.
More details in the /tonight/ discussion below.

So for today...abundance of clouds with spotty showers which would
yield some measurable precipitation on the order of a trace to a
couple of hundredths. Temperatures kept at below-seasonable levels
around the middle- to upper-50s...cooler across the high terrain and
along the coast. Sadly not very Spring-like.

&&

Short term /6 PM this evening through 6 PM Tuesday/...

The core of the upper level cutoff makes its closet approach to
S New England this evening...then starts to rotate back out to
sea late tonight into Tuesday. As it does...southern New England
gets into a pattern of decreasing moisture. In turn...this means a
lower risk for rainfall through the day Tuesday.

Winds are expected to be north to northwest tonight into Tuesday.
There is still some question if the pressure gradient relaxes
enough...and we see enough sunshine...where seabreezes could
develop. That would have a major impact on temperatures toward the
coasts. At this time...thinking the pressure gradient stays strong
enough to prevent seabreeze development Tuesday. This will need to
be monitored.

Temperatures rise slightly Tuesday with the additional sunshine...
but should still be slightly lower than normal for this time of
year.

&&

Long term /Tuesday night through Sunday/...

Highlights...

* relief on Wednesday with above average temperatures
* digging trough/coastal low on Thursday/Friday brings below normal
temperatures
* improvements for the weekend

Overview...

Closed low which has plagued the region for several days now will
eject offshore by Tuesday allowing for brief ridging on Wednesday. Still
watching two systems which will put the northeast back into a deep
trough by Thursday/Friday. Still a lot of uncertainty on how the
northern stream phases with the southern stream which has allowed
for large model spread over the past several days. Overall the 00z
guidance generally shows a stronger Ohio Valley/middle Atlantic upper low thus
leading to a farther westward surface track Thursday. The 00z GFS
is looking like a deep extreme with its upper low though...with the
gefs mean and new European model (ecmwf) supporting more moderate depth. Therefore
believe GFS to be an outlier compared the other guidance and trended
towards wpc/ec/UKMET. Once the systems phase...surface low pressure
will develop over the Carolinas and move up the eastern Seaboard.
Appears that this coastal low will stay south and east of the
benchmark...which is supported by the 12z ec ensembles. Beginning of
the weekend should be improvements as central Continental U.S. Ridge will move
eastward.

Details...

* Wednesday...high confidence.

Digging trough across the central Continental U.S. Will push a weak ridge over
the region. This will give southern New England a break in precipitation
and temperatures above normal. Coastal communities will be cooler thanks to
sea breeze development.

* Thursday and Friday...low confidence.

Still some uncertainty in this portion of the forecast. Everything
is dependent on how the low currently located over the 4 corners and
the digging northern stream waves behaves. Regardless appears deep
trough will develop putting southern New England back below normal
for temperatures. This trough will develop a coastal low off the Carolinas
and push northwards. The GFS appears to be the outlier stalling the
low inside the benchmark for several hours. Trended towards the
consistent ec which still keeps it south and east of the
benchmark...yet slightly stronger then previous runs. Believe Thursday and
Friday will be more hit of miss showers and continue to keep higher
probability of precipitation along the cape and islands for coastal system. Also knocked
temperatures down a few degrees from guidance as clouds will limit diurnal
heating.

* The weekend...moderate confidence.

Upper level trough will begin to move offshore by Saturday as weak
ridge builds over New England. May need to watch quick moving
northern stream energy which could give showers to the area on
Sunday...but overall hoping for a nice weekend with temperatures near
normal.

* Monday...low confidence.

Monday is looking warm but still uncertain on precipitation chances as
pattern will all be dependent on the Thursday/Friday system.

&&

Aviation /14z Monday through Friday/...

Forecaster confidence levels...

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

Short-term /till 0z Wednesday/...

14z update...

Today into tonight...high confidence. Low-end VFR ceilings mainly.
MVFR ceilings/visibilities with -shra...across east Massachusetts / Rhode Island...developing
towards evening and continuing overnight. Low-risk IFR for cape.
Northwest-winds backing north-NE becoming blustery.

Tuesday...moderate confidence. Ceilings improve to low-end VFR. Sea
breeze development is possible along the East Coast. Remains
blustery out north turning northwest.

Kbos taf...high confidence in taf. Low confidence on seabreeze
this afternoon. Winds back NE towards evening with better rain showers
chances.

Kbdl taf...high confidence in taf.

Outlook /Wednesday through Friday/...

Wednesday...moderate confidence. VFR conditions. Sea breeze
development possible.

Thursday into Friday...low confidence. VFR conditions with MVFR
possible in scattered showers across the eastern half coastline.
Ceilings/visibilities could be lower dependent on the track of a low pressure
system.

&&

Marine...

Forecaster confidence levels...

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

Short-term /till Tuesday evening/...

High confidence. Quiet boating weather expected into this evening.
Winds and seas start to increase late tonight into Tuesday a as
low pressure moves closer to the waters.

Enough northerly gradient anticipated Tuesday that Small Craft
Advisory conditions are probable for most of the coastal waters...
especially east of the Massachusetts shoreline. Winds gradually
diminish late Tuesday...but Small Craft Advisory conditions may
linger into Tuesday night for some of the outer coastal waters.
Issued a Small Craft Advisory where confidence is greatest. This
advisory may need to be expanded farther west with later
forecasts.

Outlook /Tuesday night through Wednesday/...high confidence.
Thursday and Friday...moderate confidence.

Wednesday...good boating weather as wind and seas will be below Small Craft Advisory.

Thursday and Friday...a low pressure system emerges from the
Carolina coastline and is expected to track northeastward. There is
considerable uncertainty in how close the center of this system
makes it to the southern New England coastline. If it stays well
offshore...swells could bring a period of rough seas to our coastal
waters. A closer approach would have significant marine impacts for
Friday. Again have undercut wna wave guidance by 40 to 50
percent.

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 4 am to 2 PM EDT Tuesday for anz232.
Small Craft Advisory from 6 am to 10 am EDT Tuesday for anz230.
Small Craft Advisory from midnight tonight to 2 PM EDT Tuesday
for anz231.
Small Craft Advisory from midnight tonight to 6 PM EDT Tuesday
for anz250-254-255.
Small Craft Advisory from 4 am to 6 PM EDT Tuesday for anz251.

&&

$$

Synopsis...Belk/dunten
near term...Belk/dunten/sipprell
short term...Belk
long term...dunten
aviation...Belk/dunten/sipprell
marine...Belk/dunten

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