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Area forecast discussion 
National Weather Service Taunton Massachusetts
1033 am EDT Tuesday Jul 7 2015

a warm front will weaken as it moves north across the region
today. A cold front moves across the region Wednesday bringing
showers and thunderstorms...some with heavy downpours. The front
moves south of New England Wednesday night and stalls...allowing
another round of showers and storms Thursday. High pressure then
builds in with fair weather for Friday and Saturday. Another
weather system approaches early next week and may bring more wet


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

1030 am update...

Warm front is beginning to push through southern New England this
morning. As it lifts northward that will put the region within the
warm sector. Biggest question is if the low stratus will burn off
in time to allow for an increase in instability. Regardless its
going to be a warm...muggy day. Scattered showers continue to pop-up
across the region with the heaviest showers south of the warm
front. Patchy fog early this morning has burned off. Something
that will need to be reevaluated for this evening.

Otherwise bulk of the forecast remains on track for this
afternoon...with the potential for a few strong thunderstorms.
Best chance is across western Massachusetts and northern CT. Cannot rule out
an isolated severe but the potential is very low at this time. Best
timing for the strong storms will be after 2 PM.

Previous discussion...

Updated the forecast to account for current conditions. Patchy fog
across CT will begin to wane as mixing and diurnal heating begins.
Otherwise a few scattered showers have developed across southeast mass...on
the edge of the threat-east advection. Not anticipated much in terms
of strong this morning...more nuisance passing showers. Anticipate
these showers to continue to move across the southern waters into
southeast mass for the next few hours.

Biggest question this afternoon is if we will get enough sunshine
to increase the instability. Both the GFS and NAM indicate around2000
j/kg of mu cape while the ec is less...closer to 1000 j/kg. The
shear is also not as impressive with around 20-30 kts of shear.
However precipitable waters are still high so if any thunderstorm does develop
this afternoon...then anticipate heavy downpours. All the hi-res
guidance is hinting at the western portion of the County Warning Area seeing the
greatest risk. Even with marginal...shear and instability...still
cant rule a very weak spin-up within the tropical airmass. Best
chance is across the CT valley where winds could back and helicity
is prognosticated to be near 100.


Short term /6 PM this evening through 6 PM Wednesday/...
expect cold front to slowly approach the region out of New York state.
Should remain dry...except for some widely scattered showers possible
across northwest Massachusetts early tonight. Have increased chance probability of precipitation after
midnight from W-E. Some short range model differences in handling
moisture with and ahead of the front...though soupy airmass
remains in place so could see scattered precipitation. Also held off mention
of thunder as best instability remains closer to the front. Will
also see fog return especially across S coastal areas especially
the cape and islands as temperatures only drop to around 70.

cold front slowly crosses the region. Best instability also moves
in by midday...with k indices in the low-middle 30s...convective available potential energy rising to
1000-1200 j/kg by midday especially across central and eastern
areas along with tq values in the upper teens signaling some
elevated convection.Big concern though is the increasing precipitable waters ...
up to 2 to 2.2 inches with good low level moisture convergence.
Could see a few strong storms though chance limited with cloud
cover...but better shot for heavy downpours which could cause
localized urban and poor drainage flooding.

Expect threat for thunder to wind down across Route 2 area around
or after 18z...with best shot for precipitation shifting to near and S of
the Mass Pike through the remainder of the day. Front looks to be
slowing as it moves S during the afternoon as well. May see
impulse move along the front which could cause training of showers
and convection...another problem for possible flooding.

Expect a warm and muggy day with dewpoints in the middle 60s to near 70
as highs reach into the middle and upper 80s across the lower CT
valley and interior east Massachusetts...even reaching the lower 80s on the
cape. Temperatures look to hold in the upper 70s on the islands.


Long term /Wednesday night through Monday/...
big picture...
upper high pressure remains in control over the Atlantic coast while
low pressure digs over the western USA. Jet flow from western
Canada rides along the US/Canadian border. The ridge shifts to the
Midwest and plains over the weekend making room for a trough to dig
over the Canadian Maritimes. Upper heights remain at or above
seasonal normals through the period. This suggests normal Summer
temperatures...although daytime highs will of course be held back on
days of heavy sky cover or strong east flow.

The dailies...

Wednesday night-Thursday...moderate confidence.
Cold front in southeast New England during the evening moves
offshore before midnight. The front then becomes aligned with the
upper flow and stalls south of the region. Shortwave in the upper
flow moves through during Thursday...generating a wave along the
front and maintaining a risk of showers Thursday. The best chance
will be south of the Mass Pike nearest the wave and the front.
Precipitable water values remain high near the South
locally heavy downpours will continue to be a concern in southern
areas. Clouds and a light east flow should keep daytime temperatures in
the 70s.

Friday-Saturday...moderate to high confidence.
High pressure builds over the region with clearing skies and light
winds. Mixing should reach to at least 850 mb and possibly to 800
mb. Temperatures at these levels would support maximum temperatures of 80-85 Friday
and middle 80s Saturday. Dew points 55 to 65 and light winds suggest
min temperatures in the same range as well as patchy fog.

Sunday-Monday...low confidence.
Changes in the operational model solutions regarding moisture in the
vertical acts to suppress precipitation in southern New England during this
period. Meanwhile a shortwave swings across northern New England
into the Maritimes...pushing a cold front through our area. It
is hard to totally kill off probability of precipitation while such a mechanism is in place.
We will maintain chance probability of precipitation for the moment and await future model


Aviation /14z Tuesday through Saturday/...
forecaster confidence levels...

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

Short term /through Wednesday/...

Today...moderate to high confidence.
Mainly VFR visibilities during the morning...then patchy MVFR ceilings
mainly along the S coast. Brief MVFR conditions in scattered showers.
Low probability of isolated afternoon thunderstorms. S-southeast wind gusts up to
20-25 knots along coast this afternoon...highest along East Coast.

Tonight...moderate confidence.
Conditions lower to mainly MVFR by 04z-05z in patchy fog. Chance
of showers across west Massachusetts/north central CT through most of the night
with chance of isolated thunderstorms through 04z. May see IFR visibilities
across east Massachusetts/RI/N CT after 06z-07z.

Wednesday...moderate confidence.
Expect MVFR to local IFR conditions in scattered showers as cold front
slowly crosses the region. Chance of afternoon thunderstorms...
some with heavy downpours.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Wednesday night through Saturday...

Wednesday night-Thursday...moderate confidence.
A cold front over southeast mass/Rhode Island in the evening moves offshore
with winds becoming north overnight and northeast Thursday but with
speeds below 15 knots. Showers moving up the front Thursday will
bring areas of MVFR ceilings/visibilities with the best chance in CT-Rhode Island and
southeast mass.

Friday-Saturday...moderate-high confidence.
High pressure brings clearing skies. VFR. Areas of IFR possible in
early morning fog.


forecaster confidence levels...

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

Short term /through Wednesday/...high confidence.

Today...expect light/variable winds becoming S-southeast by midday...then
shift to S as warm front lifts north. May see gusts up to 20-25 knots
across the near shore waters...highest on the eastern waters. Seas
build up to 4 feet...mainly across the southern waters.

Tonight...may see leftover 20-25 knots gusts this evening then will
diminish. Patchy fog develops with reduced visibilities...below 3 miles
after midnight.

Wednesday...SW winds will increase...with gusts up to 20 knots on the
southern outer waters. Expect seas to remain below 5 feet...though
may briefly reach 5 feet at times. Chance of showers/thunderstorms
some with heavy rainfall.

Outlook...Wednesday night through Saturday...

Winds and seas remain below small craft thresholds through the
period. A cold front moves offshore Wednesday night and stalls over
the southern waters. A disturbance moving along the front will bring
showers and scattered thunderstorms Wednesday night/Thursday with reduced
visibilities in any heavy downpours. High pressure brings fair weather
Friday and Saturday.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory until 10 PM EDT this evening for anz250.
Small Craft Advisory until 8 PM EDT this evening for anz231-
Small Craft Advisory until 6 PM EDT this evening for anz230.


near term...dunten
short term...dunten
long term...wtb/evt

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