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Area forecast discussion 
National Weather Service Taunton Massachusetts
1030 PM EDT Monday Jun 29 2015

Synopsis...
warmer temperatures move in Tuesday ahead of an approaching cold
front. This front will bring showers/scattered thunderstorms very
late Tuesday night and Wednesday with more showers and storms
possible Thursday as the front stalls in New England. The front
pushes south of the coast Friday with weak high pressure bringing
mainly dry and seasonable weather through the weekend.

&&

Near term /until 6 am Tuesday morning/...
1030 PM update...

Light showers from earlier this evening have dissipated. Still
have scattered areas of high stratocumulus/low altocumulus
clouds...with some cirrus for good measure. Light south to
southwest winds have become established...and will likely persist
through the overnight. No major changes to the previous forecast...
but did tweak temepratures from now into Tuesday morning to
reflect observed trends.

Previous disucssion...

Low temperatures will drop into the 50s in most locations with some lower
60s possible at a few locations. Patchy ground fog may develop
late in the typically prone locations...but not expecting anything
widespread.

&&

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

A partly sunny and pleasant day in store for the region. High temperatures
mainly in the lower 80s...but cooler middle to upper 70s are
expected on portions of the coast with sea breezes. Upper
trough/shortwave will result in showers and thunderstorms developing
across portions of New York state and Pennsylvania during the
afternoon. Across our region...upper level ridging will generally
result in dry weather. May see just enough instability for an
isolated brief shower/thunderstorm or two in far northern zones and
especially northwest Massachusetts late Tuesday afternoon/early evening.

Tuesday night...

Other than an evening isolated spot shower/thunderstorm in northern
or northwest Massachusetts...dry weather will dominate through midnight.
However...potent shortwave and associated cold pool aloft will
approach from the west toward daybreak. Timing uncertain...but some
of the models show showers and thunderstorms working into parts of
the region between 9z and 12z. Timing is uncertain and the bulk of
the action may hold off until after 12z. If activity does arrive
early...may see quite a bit of elevated convection in our western
zones given 500 mb temperatures around -12c and middle level lapse rates
around 6.5c/km.

&&

Long term /Wednesday through Monday/...
highlights...

* showers and thunderstorms likely Wednesday...some storms may be
strong with locally heavy rainfall
* continued threat of showers and thunderstorms Thursday
* looking mainly dry and seasonable Friday through the 4th of July
weekend but confidence is not high

Overview...high amplitude trough for this time of year across the
Great Lakes with series of shortwaves rotating into new eng will
bring a period of wet weather Wednesday and Thursday. Models have been
struggling with the location of a frontal wave toward the end of
the week. Previous runs of the GFS and European model (ecmwf) were quite wet here
Thursday night into Friday but 12z runs are now suppressed and keep it dry
here right through the weekend with weak high pressure over new
eng. However...given proximity of a series of waves just to the
south...confidence in a dry forecast is not high as a slight
northward shift would mean a cool rain.

Wednesday...interesting set up as showers and scattered thunderstorms will
likely be moving into southern New England first thing in the morning as middle level
shortwave approaches from the west and warm front moves up from
the SW. All models are generating decent surface instability greater
than 1000 j/kg by 18z due to favorable middle level lapse rates. This
combined with good large scale synoptic forcing and deep layer
moisture suggests numerous showers and scattered thunderstorms moving west to
east across southern New England during the morning and into the afternoon. Good
500 mb jet punching into the region results in 0-6km shear of
40-45 knots which is rather impressive. If instability can be
realized we cant rule out a few strong to severe storms Wednesday
morning into early afternoon but it could also just be a batch of
showers and weaker storms of instability is weaker as warm front
not likely to lift to the north until the afternoon. It is
possible however that the cool air aloft associated with the middle level
shortwave and resulting steep lapse rates helps to maintain decent
surface instability. This is something that will need to be monitored
but locally heavy rainfall will also be a threat. The main
question for later in the afternoon is if a second round of
showers/thunderstorms can develop in the interior ahead of a cold front.
Models are drying the column late in the day so there is limited
window for a second round of convection. Also deep layer shear is
weakening after 18z. Temperatures mostly in the 70s but it will become
humid with dewpoints climbing well into the 60s.

Thursday...cold front likely gets hung up across southern New England as another
middle level shortwave approaches from the Great Lakes. Models show
destabilization occurring with up to 1000 j/kg of SBCAPE and a
surge of higher ki values moving back into the region so more
showers and thunderstorms are possible especially in the afternoon with
focus more in central and east new eng. 0-6 km shear is 35-40 knots so
if instability is realized cant rule out a few strong storms but
middle lapse rates will be a limiting factor.

Friday through Monday...not a high confidence forecast but latest
guidance is suggesting mostly dry and seasonable conditions with a
warming trend by Sunday as a series of waves remain to the south
through Sat with weak high pressure in control. However...any slight
northward adjustment would result in cooler and wet weather Friday
and Sat.

&&

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

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

Short term /tonight through Tuesday night/...

02z update...

Tonight...high confidence. VFR conditions continue for the rest
of the night...other than perhaps a few hours of patchy ground fog
late in the typically prone locations.

Tuesday...high confidence in mainly VFR conditions. An isolated
spot shower/thunderstorm or two is possible in the afternoon across
portions of our northern zones...with the best shot in far northwest
Massachusetts.

Tuesday night...low confidence. VFR in the evening. May see some
low clouds develop late in some locations with the best shot for
this along the southeast New England coast. May also see an area of
showers and thunderstorms work into western New England toward
daybreak...but confidence on that is also low.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Wednesday through Saturday...

Wednesday...high probability for widespread showers with scattered thunderstorms.
Risk of a few strong storms and heavy rainfall. IFR and MVFR
conditions likely.

Thursday...moderate confidence. Mostly VFR...but scattered showers/thunderstorms
possible in the afternoon with MVFR conditions.

Friday and Sat...low confidence. VFR with mostly dry conditions...but
it could still end up wet if waves of low pressure track further north.

&&

Marine...
forecaster confidence levels...

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

Short term /tonight into Tuesday night/...high confidence.

Tonight...leftover swell of 3 to 6 feet will continue across the
southern coasta waters. Small Craft Advisory headlines continue
accordingly.

Tuesday and Tuesday night...weak pressure gradient will keep
winds/seas below Small Craft Advisory thresholds. Some fog may
develop toward daybreak Wednesday across our southern waters.

Outlook...Wednesday through Saturday...

Wednesday...high confidence. SW wind gusts to 20 knots with Small Craft Advisory seas over
southern waters. Visibilities limited in showers and scattered thunderstorms and
areas of fog.

Thursday...high confidence. Light SW winds but leftover southerly swell
will result in Small Craft Advisory seas over southern waters. Scattered showers/thunderstorms
possible in the afternoon.

Friday and Sat...moderate confidence. Light easterly winds. Marginal
Small Craft Advisory seas possible southern waters on Friday.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 5 am EDT Tuesday for anz235-237-
254>256.

&&

$$
Synopsis...kjc/Frank
near term...Belk/Frank
short term...Frank
long term...kjc
aviation...Belk/kjc/Frank
marine...Belk/kjc/Frank

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