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Area forecast discussion 
National Weather Service Taunton Massachusetts
1009 PM EDT Friday Aug 29 2014

high pressure over New England will provide dry and cool weather
through Saturday morning. Temperatures will begin to moderate
Saturday afternoon as the high drifts offshore. By Sunday very
warm and humid conditions overspread the area as a cold front
approaches the region from the west. This may result in few
thunderstorms later Sunday into Monday and possibly Tuesday. Dry
and seasonable weather is expected behind the front for the middle
of next week.


Near term /until 6 am Saturday morning/...

One patch of clouds moving east of Massachusetts. A broader area
of clouds over Ontario is shifting east...and may reach the CT
valley/Berkshires around 5 am. Otherwise clear skies and light
winds are in place and should continue for most of the night.

These conditions support radiational cooling. Surface temperatures at 10
PM were approaching dew point at several spots such as tan and
Oregon. We expect areas of radiation fog to develop overnight
especially in the colder valley of the interior and in some of the
low spots of eastern mass. Local visibilities below 1/2 mile possible.

Min temperatures will be guided by dew point the upper 40s
and 50s.


Short term /6 am Saturday morning through Saturday night/...

Real nice day once early morning patchy fog/low clouds burn off. Middle
level ridge axis is centered over the area yielding anticyclonic
flow providing dry weather and a fair amount of sunshine. Likely to
see today/S moisture remain trapped beneath subsidence inversion so
another round of scattered-broken strato-cumulus expected. As low level winds
become south-southwest airmass will modify somewhat with highs tomorrow in the
mu 70s except l70s along the South Coast given the onshore winds.

Saturday night...

Warm front moves across the area so expect more humid conditions
with dew points climbing into the 60s. Cross sections suggest moisture
is fairly shallow so not expecting much precipitation other than possibly
areas of drizzle. Thus low clouds will be on the increase. The cloud
cover and higher dew points will result in warmer conditions than
previous nights along with patchy fog.


Long term /Sunday through Friday/...
*/ highlights...

- prolonged period of showers and thunderstorms Sunday into Monday
- cold front sweeps New England around Tuesday
- dry and quiet weather for the remainder of the week

*/ overview and model preference...

Continued preference of seasonable to above average temperatures
associated with weak ridging of a zonal-flow pattern into early
September signaled by a negative to near-neutral nao / pna. With
lesser magnitude of wind through all levels emphasized by
ensembles not expecting robust-amplified systems...rather a
subdued weather- pattern. Anticipate impulses through the zonal-
flow regime with the bulk of activity edged north by weak ridging /
higher heights...though trailing over the NE-Continental U.S. To allow
periods of disturbed weather /thinking mainly sub-severe/ and
brief-shots of refreshing air.

Still favor the European model (ecmwf) / ecens with decent run-to-run consistency.
Feel the GFS is close to following suit. Do not favor the 29.12z NAM
after 0z Monday. Highlights/confidence are broken down in the daily
discussion below.

*/ Day-to-day details...

Sunday into Monday...

Would expect scattered showers with daytime-instances of thunder-
storms as a weak disturbance slides across the region. Bulk-forcing
per positive vorticity advection within a middle-level conditionally
unstable profile /h85-7/ above a low-level moist-unstable axis
should allow for favorable ascent...strongest of which during the
day with well-mixed boundary-layer profiles / positive buoyancy.

Difficult to nail down exactly where and when activity will develop.
Thinking initial activity on Sunday will be across the north/west interior
closer to bulk-forcing and along the S/W-slopes of higher terrain
with orographic lift...wherever ascent is possible as the convective-
temperature is met to break the cap of a lingering dry-subsidence
inversion. With 0-6 km bulk shear /around 30 kts/ and freezing-level
heights of around 14-15 kft...expect only a few strong storms. Very
little in the way of jet dynamics. Will only entertain the threat of
heavy rain with precipitable waters exceeding 2-inches...though isolated as deep-
layer forcing is lacking. Ordinary to multicellur storms considered
based on convective indices. Warm and muggy with breezy S/SW winds.

Activity diminishes Sunday evening and overnight with the conclusion
of daytime-heating and as energy stretches to the NE of the dominant
west-Atlantic ridge. Showers still anticipated with middle-level moist-
convergence and ascent within a continued conditionally unstable
profile sliding southeast towards the waters.

Not as convinced as earlier that there will be a lot of activity on
Monday. Could be an isolated show where forcing is present within a
lingering moist-unstable profile. Its likely wherever the convective
temperature can be met will showers and thunderstorms generate. Feel
bulk of energy shifting S/east and undergoing stretching through the
zonal-flow will result in weaker dynamics. Activity concludes
into the nighttime hours with activity east. Should turn quiet.

Tuesday into Wednesday...

Considering the following: early-week energy is stretched offshore
along the west-periphery of the west-Atlantic ridge. Cold front pushes in
from the west with parent dynamics shifting northwest well into Canada. A low-
level moist-unstable plume re-surges into the NE-Continental U.S. Collocated
with an environment of decent middle-level lapse rates. Ridging still
prevails over the region.

While some scattered shower / thunderstorm activity is possible...
feel it will be confined to the north / west interior. Southeast may find itself
beneath subsidence between the two systems mentioned above. Best
chance is during the day Tuesday within decent instability and some
shear around 15-20 kts. Dynamics lacking and weak ridging is still
in place.

Thursday into Friday...

Will prevail with the European model (ecmwf) of zonal-flow and higher heights. High
pressure in control. Seasonable conditions with some cool nights.

Next weekend...

Another cold front potentially slides across the region...stretching
and becoming diffuse as it progresses southeast towards a west-Atlantic ridge


Aviation /02z Saturday through Wednesday/...
forecaster confidence levels...

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

Short-term /through Saturday night/...high confidence.

Mostly VFR. MVFR-IFR ceilings and visibilities due to patchy fog possible for
CT-and Merrimack-valley well as immediate interior
locales away from the shore. Patchy in coverage...will erode with
sunrise. Light and variable winds.

Saturday...VFR in scattered-bkn035-045 during the afternoon hours. Low
risk of more widespread MVFR ceilings bkn020-030 across Rhode Island and
southeast Massachusetts. Southeast winds becoming more S in the afternoon. Dry
weather/runways continue.

Sat night...increasing risk of MVFR ceilings and visibilities. Should remain
dry. S winds become more south-southwest during the night.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Sunday through Wednesday...

Sunday into Monday...moderate confidence.

Rain showers throughout the period with daytime-instances of thunderstorms and rain. Breezy S-
winds. Mix of low-end VFR to MVFR...possible IFR along the S-coast
Sunday and Monday morning prior to activity pushing offshore towards
Tuesday morning.

Tuesday...moderate confidence.

Cold front with some rain showers/thunderstorms and rain for north/west New England. Lower confidence
S/E. Low-end VFR ceilings with wet-weather.

Wednesday...moderate confidence. VFR.


forecaster confidence levels...

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


Pleasant boating weather with light winds and diminishing southeast swell.
Visibility may lower in fog toward morning near shore.

Saturday...other than some patchy morning fog near shore expect good
visibility and dry weather. High pressure begins to slide offshore so winds
become south-southwest.

Sat night...warm front moves across the waters so patchy fog and
drizzle possible. A modest south-southwest wind expected.

Outlook...Sunday through Wednesday...

Sunday into Monday...moderate confidence.

Breezy S/SW-winds with gusts up to 25 kts. Wave heights in excess of
5-feet across the S/southeast waters. Showers encroaching upon the waters
late Sunday and continuing through Tuesday morning. Fog possible
during the overnight hours along the S-coast though low confidence.

Tuesday into Wednesday...moderate confidence.

Cold front sweeps across the waters...but expecting just a few
showers...mainly dry. Wave heights below 5-feet. Winds remaining
below 25 kts.


Box watches/warnings/advisories...
New Hampshire...none.
Rhode Island...none.


near term...wtb
short term...nocera
long term...sipprell

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