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Area forecast discussion 
National Weather Service Taunton Massachusetts
954 am EDT Monday Aug 3 2015

Synopsis...

Dry weather prevails much of today then the threat of showers and
thunderstorms returns late tonight towards Tuesday morning. Dry...
warm and less humid weather arrives Wednesday and continues into
Thursday. A period of unsettled weather is possible Thursday night
into Saturday...but confidence is low on the timing of potential
wet weather.

&&

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

10 am update...

Scattered showers some of which evolving into thunderstorms have
erupted southeast of New England over the waters. Beneath favorable middle-
level lapse rates along a low- to middle-level gradient of higher
Theta-E air...convergence is lending to development. But activity
is staying low and not becoming robust due to the absence of deep
layer forcing. Only instability and convergence of moisture are
aiding in the process within an environment of bulk shear values
of around 25 kts. Collocated upper-level jet streak and attendant
venting aiding as well.

Feel the environment will continue through the day and thus have
increased the rain chances across the southeast waters. Uncertain as to
precipitation chances over the cape/islands. Will have to watch closely
and as to whether we can generate some upper-level support via a
collocated aforementioned 300 mb jet streak. Again...forcing appears
to be convergent related so with any later activity feel it will
remain sub-severe.

Otherwise a warm and humid day especially for southeast New England as
temperatures top out into the upper-80s to low-90s with dewpoints
around the mid-60s. Drier north/west with upper-50 to low-60 dewpoints. A
mix of sun and clouds under breezy SW-winds gusting 20-25 miles per hour.

Agree with the prior forecast team that little height falls are
anticipated today beneath middle-level dry air per 12z soundings.
Ridge should hold in place across the region keeping our area dry.
Thus convective activity should remain mostly north and west but it is
not out of the question that the remnants as well as the convective
environment of better instability and forcing can drift into northwest Massachusetts
towards the end of the period into evening with the mean wind.
Chance probability of precipitation for now.

&&

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

*** possible strong to severe T-storms later tonight into Tuesday ***

Tonight...

More potent trailing short wave trough approaches southern New
England from the west. This is quite evident in wind fields aloft
where 500 mb speeds approach 50 kts! This short wave trough cools 500 mb
temperatures to -11c/-12c. This combined with surface dew points increasing
into the u60s and l70s provides MUCAPES greater than 2000j/kg and
middle level lapse rates between 6.5 and 7.0c/km by 12z Tuesday across Rhode Island
and eastern Massachusetts per 00z ec and 00z GFS! Even the course 00z gefs has
the same signal and strength. This amount of instability combined
with deep layer shear up to 50 knots provides an environment favorable
for severe storms. Only uncertainty is will there be enough forcing
for ascent to unleash this strong instability. Mixed signals within
the guidance with the GFS and European model (ecmwf) not generating much quantitative precipitation forecast tonight
while the hi res guidance nmm and arw have convection but weakening as
it crosses the area from west to east. Somewhat discounting the NAM
given it/S high biased dew points and corresponding instability
parameters.

Thus low forecast confidence on areal coverage and intensity of
convection. However if storms can fire strong to damaging winds will
be a concern. Low level shear is impressive too along with
sufficient instability and low LCLs /high dew points/ for a low risk of
an isolated tornado.

It will be a warm and humid night with dew points rising through the
u60s and l70s.

Tuesday...

Forecast uncertainty continues as areal coverage of nocturnal
convection and cloud debris from tonight will impact if new
convection fires during the day Tuesday. Short wave trough moves across
the area along with attending surface trough. This should provide
enough forcing for ascent to initiate convection. Deep layer
moisture and instability appears to be focused across Rhode Island and eastern
Massachusetts. Thus risk of storms greatest across this area. Winds fields
remain impressive so risk of strong to damaging winds continues.

Another warm day with highs well into the 80s along with dew points in
the u60s to l70s.

&&

Long term /Tuesday night through Sunday/...

Highlights...

* unsettled weather possible around Friday
* temperatures trending below normal during this period

Overview...

00z guidance is in descent agreement for this portion of the
forecast. Upper level low over James Bay will begin its eastward
movement towards the Maritimes. Elongated trough will set up over
the region before trending towards a zonal flow. Several southern
stream waves will move through and tries to bring a few coastal
systems towards southern New England. The pattern does not seem that amplified to
make it a classic coastal low...however upper level jet may bring a
few systems just south of the region. Because of the uncertainty at
the end of the week...trended towards the ensembles which indicate
precipitation around late Thursday into Friday and again possible
Saturday/Sunday. This unseasonable pattern will lead to below normal
temperatures toward the end of the week into the weekend.

Dailies...

Wednesday into Thursday...moderate confidence.

A few lingering showers and thunderstorms over the waters as cold
front passes through late Tuesday night.

Shortwave will push through on Wednesday as high pressure builds in
from the west. Upper level trough will allow for cyclonic flow and
cold air aloft...resulting in a few afternoon instability showers
across the higher terrain. Otherwise it will be a mix of clouds and
sunshine.

Cyclonic flow will still be aloft by Thursday but cold air aloft
will be focus more across northern New England. Therefore believe
Thursday will be dry with a mix of sun and clouds.

Temperatures will be cooler than normal both days with southern New England reaching
into the 80s on wednesdays but below 80 on Thursday.

Thursday night into Friday...moderate confidence.

Potent shortwave will try to develop a southern wave during the end
of the work week. Both ensemble members as well as the operations
ec brings precipitation to the region during this time frame. Therefore
have increased precipitation chances across the South Coast where
confidence is highest. Southern New England will be on the northern side of this
system so any shift in the pattern will move the precipitation chance for the
region. Finally being on the north-side of the system...temperatures
will be unseasonable cooler. In fact temperatures will struggle to
get above 80f.

Saturday and beyond...moderate confidence.

Another southern stream wave tries to develop over the weekend. Low
confidence on if the pattern will bring this low to southern New England. Have kept a
low chance as guidance continues to flip-flop during the timeframe.
Otherwise...temperatures will begin to moderate over the weekend
into next week as upper level ridge over the Continental U.S. Begins to build
again.

&&

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 /through Tuesday/...

Today...high confidence.
VFR and dry. Thunderstorms and rain in New York state this afternoon may clip west late. South-southwest
winds increasing with gusts up to 20-25 knots.

Tonight...low confidence.
Lots of uncertainty on areal coverage and intensity of potential
thunderstorms and rain. VFR to start but lowering to MVFR and probably IFR in low
clouds and fog across Rhode Island and southeast Massachusetts.

Tuesday...low confidence.
Lots of uncertainty on areal coverage and intensity of potential
thunderstorms and rain. A mix of MVFR and IFR in the morning as low clouds and fog
impact the terminals. Likely improving to VFR in the afternoon.

Kbos terminal...high confidence in taf today then lowering tonight
and Tuesday.

Kbdl terminal...high confidence in taf today then lowering tonight
and Tuesday.

Outlook /Tuesday night through Friday/...

Wednesday...moderate confidence. Mainly VFR. Could see MVFR in
showers across higher terrain.

Thursday into Friday...low confidence. A period of showers and
MVFR/IFR possible but timing is uncertain. Latest indications are
that best chance for wet weather will be on Friday.

&&

Marine...

Forecaster confidence levels...

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

Short-term /through Monday night/...

Today...high confidence.

South-southwest winds increase to 15 to 20 knots with gusts up to 25 knots. Seas
increase especially across the south coastal waters.

Tonight...moderate confidence.

South-southwest winds 15 to 20 knots. Gusts up to 25 knots possible. Patchy fog will
limit visibility. A few strong T-storms possible especially after
midnight. Low confidence on T-storm forecast.

Tuesday...moderate confidence.

South-southwest winds 15 to 20 knots with gusts up to 25 knots possible. Patchy
morning fog may reduce visibility. A few strong T-storms possible. Low
confidence on T-storm forecast.

Outlook /Tuesday night through Friday/...moderate confidence.

Wednesday...moderate confidence. West/SW winds below Small Craft Advisory but gusts to
20 knots possible. Seas subsiding.

Thursday into Friday...low confidence. Winds and seas will depend on
track and timing of low pressure approaching the region. Could see a
period of gusty NE winds...especially Friday.

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 4 PM this afternoon to 8 PM EDT
Tuesday for anz230>237-250-251-254>256.

&&

$$

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

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