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Area forecast discussion 
National Weather Service Taunton Massachusetts
1002 PM EDT Tuesday Jul 28 2015

Synopsis...
isolated to scattered thunderstorms will come to an end this
evening. Otherwise...hot and humid conditions expected through
Thursday. A cold front will bring scattered thunderstorms late
Thursday and Thursday night. Warm and less humid weather is
expected Friday into the weekend. There will be chances for more
showers and thunderstorms late this weekend into early next week.

&&

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

10 PM update...

Overall trend in the forecast is on track. Biggest issue tonight
is the humid airmass which will increase the fog potential especially
for areas that received rain today. Several locations have
already dropped down to a mile or less...and expect this trend to
continue overnight. Will monitor for possible dense fog advection.

Previous discussion...

Expect dry weather to prevail for the rest of the night. Low
temperatures will range from the lower to middle 60s in the outlying
locations with upper 60s to lower 70s in the urban heat islands of
downtown Boston and Providence.

&&

Short term /6 am Wednesday morning through 6 PM Wednesday/...
***hot but dry weather on wednesday***

Upper level riding will build across southern New England. This
should result in partly to mostly sunny skies...despite some
diurnal cumulus clouds. 850 mb temperatures around +18c will yield highs
between 90 and 95 across most of the region. Weak pressure gradient
will result in temperatures a bit cooler along portions of the coast.
While there is a low risk of a very isolated
shower/thunderstorm...given upper level ridging opted for a dry
forecast. Even if one were to happen it probably would be very
brief and cover such a small area of our region...not Worth a
mention at this point.

&&

Long term /Wednesday night through Tuesday/...
synoptic overview and model preferences...

As 500 mb cutoff low sets up across Hudson Bay/Ontario/W Quebec and a
negative nao pattern in place...a fast upper flow will continue
across the northern stream through this period. Short waves in this
flow will bring chances for showers/thunderstorms...though timing of
each individual system is in question beyond Friday due to the fast
flow. May start to see this long wave pattern break down early next
week...though low confidence on this timing this far out.

Noted very good continuity and timing of approaching system late
this week amongst the medium model suite...then timing and placement
of systems this weekend into early next week in question. So...
went with a blend of 12z GFS/00z European model (ecmwf) op model runs through Friday
night...then transitioned over to an overall blend of available
guidance including gefs/ecens later in the period which gave good
consistency.

Wednesday night...
weak short wave ridging will cross the region Wednesday night. Will see
sultry conditions...which will likely lead to patchy fog which may
become locally dense along the S coast...Cape Cod and the islands
after midnight. Expect overnight lows in the upper 60s to lower
70s though a bit milder in the urban centers.

Thursday through Friday night...
pretty vigorous 500 mb short wave moves along in west-northwest flow aloft.
Current timing suggests arriving after 18z Thursday across the east
slopes of the Berkshires than pushing into the CT valley late in
the day. Looks like most action will occur Thursday night into Friday as
front moves slowly but steadily across. With good push of drier
air behind this front...noting precipitable waters increase to 1.9 to 2.1 inches
during the night with highest values across S coastal areas. Also
good elevated convection signals...with tq values in the low 20s
along with k indices in the middle 30s. Storm Prediction Center has also mentioned
marginally severe conditions as the precipitation moves into far western
areas late in the day. Something to be watched.

Have likely showers/scattered thunderstorms moving across the region overnight.
Also used enhanced wording for heavy rainfall.

Expect front to clear the coast Friday morning. Isolated thunder may
linger through middle morning as best instability moves offshore.
Some showers may linger across the cape and islands until around
midday then should exit. Noting a brief break in the humid
conditions as dewpoints fall back to the 50s away from the coast.
Temperatures will still be warm though...with highs mainly in the Lower-
Middle 80s.

Friday night will be dry and comfortable especially across
central and west Massachusetts into north CT. Expect lows in the 60s...though may
linger around 70 across the Outer Cape and islands.

Saturday-Sunday...
noting another dip in the long wave trough across the Great Lakes
as a short wave moves in the upper flow. Operational models having
trouble handling this feature...though does look like there may be
some isolated shower/thunderstorm activity as weak front crosses Sat night
into Sun morning. Looks like best shot for now will be across the
CT valley and along East Coast...though could see isolated activity
anywhere. Somewhat lower confidence during this timeframe.

Monday-Tuesday...
the 500 mb closed low over Hudson/James bays hints in shifting slowly
east across north Quebec during this timeframe...but still seeing long
wave troughing across the Great Lakes. May see periods of
showers/thunderstorms mainly during the daylight hours both Monday and
Tuesday...though some question on exact timing this far out. Will
remain warm and humid during this timeframe.

&&

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

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

Short term /through Wednesday afternoon/...

Tonight...moderate confidence. VFR for many sites...however
anticipate patchy dense fog to develop dropping some sites down
to IFR or even LIFR. Best spot will be across the cape...islands
and South Coast where dewpoints are in the 70s.

Wednesday...high confidence in VFR conditions.

Kbos terminal...high confidence.

Kbdl terminal...high confidence.

Outlook /Wednesday night through Sunday/...

Wednesday night...moderate to high confidence. Will see patchy
fog with MVFR-IFR conditions mainly near or after midnight.

Thursday...moderate confidence. Patchy MVFR-IFR in fog improving
to VFR by middle morning. However...low probability that MVFR-IFR in low
clouds and patchy fog may linger along the South Coast. Chance of
showers and thunderstorms move into western areas after 18z...then
shifting east by evening.

Thursday night...moderate confidence. Patchy MVFR ceilings/visibilities in
scattered showers/thunderstorms. Locally heavy rainfall likely...
especially across Rhode Island/southeast Massachusetts around or after midnight. Improving
conditions after midnight across north central and west Massachusetts into north central
CT.

Friday and Saturday...moderate to high confidence. Lingering
showers/isolated thunderstorms and patchy fog along S coast...
otherwise mainly VFR through the remainder of Friday through Sat.
Isolated showers/thunderstorms possible Sat night with local MVFR conditions.
Lower confidence on timing.

Sunday...moderate confidence. Mainly VFR.

&&

Marine...
forecaster confidence levels...

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

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

Winds and seas will remain below Small Craft Advisory thresholds
through Wednesday afternoon. Main concern will be a few strong to
severe storms across the adjacent south coastal waters through 7 or
8 PM. Locally strong wind gusts and perhaps isolated hail are the
main concerns. Also...some patchy fog is possible this evening near
the islands but visibilities should improve after midnight as winds
turn west.

Outlook /Wednesday night through Saturday/...

Wednesday night and Thursday...expect light SW winds Wednesday night
into Thursday...then picking up during Thursday afternoon. May see gusts to
20 knots. Seas 4 feet or less. Patchy fog Wednesday night into Thursday morning
lowering visibilities.

Thursday night...SW winds gusting to 20 knots mainly over the open
waters. Seas reaching around 5 feet. Patchy fog along with scattered
showers/thunderstorms lowering visibilities.

Friday and Saturday...cold front slowly moves offshore. Another
weak front may enter the waters late Sat or Sat night. Seas over
the open waters up to around 5 feet during Friday...subsiding Friday
night but may build again Sat night.

Sunday...winds and seas below small craft criteria.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...air quality alert from 11 am to 11 PM EDT Wednesday for
maz017>024.
Rhode Island...air quality alert from 11 am to 11 PM EDT Wednesday for
riz005>008.
Marine...none.

&&

$$
Synopsis...Frank/evt
near term...Frank/dunten
short term...Frank
long term...evt
aviation...Frank/evt/dunten
marine...Frank/evt

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