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Area forecast discussion
National Weather Service Taunton Massachusetts
151 am EDT Mon Jun 26 2017

Synopsis...
scattered showers and isolated thunderstorms will diminish by
midnight. Additional upper level disturbances move across New
England on Monday and Tuesday, bringing a few showers or
isolated thunderstorm. Then a warming trend begins for the
latter half of the week with a return to Summer heat and
humidity by Friday. A warm front may bring some showers Thursday
with more showers and thunderstorms possible Friday and
Saturday. A backdoor front may drop south into the region
Saturday.

&&

Near term /until 6 am this morning/...
150 am update...
showers have diminished as shortwave is lifting to the NE with
subsidence behind it. Noting a small area of showers moving east
from Li which may clip the South Coast and cape/islands early
this morning so have slight chc pops. Otherwise, trend will be
for clearing skies.

&&

Short term /6 am this morning through 6 PM Tuesday/...
upper flow remains cyclonic. A weak shortwave moves through the
flow and across New England on Monday. Temps aloft will be a
couple of degrees cooler, with solar heating working on the
surface temperatures. The resulting lapse rates should be
favorable for a few showers/tstms.

Mixing will again reach high, up to 800 mb or a little higher.
Temps at that level, equivalent to 11c at 850 mb, will support
Max temps in the upper 70s and the low 80s.

Convection will again diminish after sunset with clearing skies
and light wind. With dew points in the 50s, expect min temps in
the 50s and low 60s.

&&

Long term /Tuesday night through Sunday/...
highlights...

* a few showers/isold T-storm possible Tue/Wed
* warming trend toward end of the week with return to Summer
heat/humidity by Fri
* thunderstorm chances increase Thursday night through Saturday
* low confidence - backdoor front possible far northeast Massachusetts Sat.

Overview...

Mid level trough exits New England Wed., Followed by building
heights as subtropical ridge builds over the western Atlantic.
Polar jet will be in the vicinity of new eng next weekend which
will leave US susceptible to weak shortwave passages. A warm
front will meander back and forth near the Massachusetts/New Hampshire border Friday
through Sunday with a series of weak low pressure systems moving
along the boundary. Thus the chance of showers and
thunderstorms will increase as we head into the weekend.

Details...

Tuesday and Wednesday...

Strong mid-level shortwave trough lifts northeast from the Great
Lakes Tue with axis of the trough moving into New England by
Tue. Evening before exiting on Wed. With 500 mb temps cooling
to -18 to -20c, will see scattered showers and isolated
thunderstorms. The best chances, where k indices reach 25-30
along with total totals greater than 50, will be in the
northwest half of the region, west of a line from northern CT to
the Merrimack valley.

For the second run in a row, the ecwmf shows a surface trough
south of New England, which creates an area of rain showers for
south coastal Rhode Island and southeast Massachusetts Tue. Night into early Wed.
Morning. Will forecast a chance of showers there.

On Wed, mid level trough exits the region. There will still be a
cold pool aloft, hence total totals indices in the lower 50s.
However, the column will be drying out with westerly winds and
k indices struggling to surpass 20-25. Cannot rule out a slight
chance of a few showers. But not expecting thunder.

Highs both Tue. And Wed. From 77 to 80 in the interior.

Thursday...

Increasing warm advection pattern as warm front approaches from
the SW will lead to increasing clouds. Southwesterly low level
jet is forecast to increase to 40-50 kt at 850 mb by late in the
day. Despite some cloud cover temperatures will rise to the mid
80s and this will allow for mixing to create wind gusts to 20-30
mph, especially in the coastal plain.

GFS and European model (ecmwf) now in agreement that the warm front will move to
near the Massachusetts/NH/VT border by Thu. Evening. There is a pronounced
increase in k indices as high Theta-E air moves in from the
west. The implication is that a cluster of thunderstorms,
possibly severe to our west, will travel eastward along the warm
front, aided by swift 55-70 kt west winds at 500 mb. There is a
good chance of thunderstorms in northern and western Massachusetts late
Thu. Afternoon and Thu. Night as a result, with scattered
storms possible elsewhere Thu. Night.

Friday and Saturday...

Somewhat tricky forecast due to placement of active frontal
boundary. Very unstable air mass in place both Fri. And Sat.
High temperatures will reach well into the 80s with near 90
possible. Dewpoint temperatures are forecast to hover between
the upper 60s and lower 70s. The frontal boundary is forecast to
become quasi- stationary near the Massachusetts/VT/NH border by
Saturday...and it may even shift southward a tad as a backdoor
cold front into the Cape Ann region on Saturday.

Several thousand joules of cape are possible on either day.
Scattered thunderstorms are expected both days and there is the
potential for severe weather, with wet microbursts a possibility.
Helicity values could be higher near the Massachusetts/NH/VT border, close
to the front, which may add to severe potential.

Sunday...

Tricky forecast continues...with models suggesting a slow moving
surface trough and a continued chance of scattered showers and
thunderstorms. Highs mainly in the mid 80s due to cloud cover,
but subject to change...could be higher if more sunshine.

&&

Aviation /06z 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/...high confidence.

Through 12z...
VFR. A brief shower may clip immediate South Coast and
cape/is;ands through 08z, otherwise clearing skies.

Monday...
VFR with sct-bkn cu 5-6k ft developing, mainly north of the
South Coast region. Sct showers and isold T-storms expected to
develop in the afternoon in the interior.

Monday night...
VFR. A few lingering showers or an isold T-storm interior
early, otherwise areas of mid level clouds.

Tuesday...
VFR with bkn cigs 5-7k ft. Sct showers and T-storms expected
from midday through the afternoon which may bring briefly lower
conditions.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Tuesday night through Friday/...

Tuesday and Wednesday...high confidence.
Mainly VFR. A few showers and isold T-storms possible Tue and
still can't rule out a shower on Wed.

Thursday...moderate confidence.
Mainly VFR with cigs lowering from northwest to southeast. Afternoon showers
possible in the interior with showers/T-storms possible all southern New England Thu
night. Gusty SW winds to 25-30 kt developing, especially
coastal plain.

Friday...moderate confidence.
Patchy early morning fog, with local MVFR. Then VFR, except
local IFR in possible strong thunderstorms, mainly during the
afternoon and evening hours. MVFR in patchy fog late Friday
night, especially South Coast.

&&

Marine...
forecaster confidence levels...

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

Short term /through Tuesday/...high confidence.

High pressure offshore with west to southwest winds. Speeds
should remain 20 knots or less. Seas have diminished, and should
remain at 4 feet or less through the period.

Outlook /Tuesday night through Friday/...

Tuesday and Wednesday...high confidence. Quiet boating weather with
winds and seas below Small Craft Advisory. Gusts to 20 kt possible nearshore waters.

Thursday...moderate confidence. Small craft advisories will
likely be needed. Increasing SW winds with gusts to 25+ kt
likely, especially over nearshore waters. Building seas may
reach 6 to 8 ft over southern waters Thu night. Chance of
showers and thunderstorms Thursday night.

Friday...moderate confidence. SW winds continue, mainly 20-25 kt
with seas 4-8 ft over the southern waters and 3 to 6 ft over the
eastern waters. Scattered thunderstorms, some with reduced
visibilities and strong gusty winds.

&&

Tides/coastal flooding...
high astronomical tides have peaked at most spots, but still at
high levels for at least one more cycle. The overnight tide
cycle will be the one of concern, with Boston reaching 12.2 feet
after midnight tonight. Tidal departures will be around 0.3 to
0.4 feet along the Massachusetts East Coast. This means
conditions will be high enough along the mass East Coast for at
least some minor splashover at high tide.

Subsequent high tides will be trending lower, and thus less of a
risk for splashover concerns.

&&

Equipment...
kbox radar is down. Technicians have been notified and will be
looking into the problem.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

$$
Synopsis...wtb/gaf
near term...kjc
short term...wtb
long term...gaf

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