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Area forecast discussion 
National Weather Service Taunton Massachusetts
132 PM EDT Friday Jul 25 2014

high pressure centered over the Ohio Valley today will pass to the
south of New England Saturday. A warm front will move across the
region Sunday bringing warm and humid air. A cold front then swings
across the region Monday...then lingers along the Massachusetts
coast Tuesday and Wednesday.


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

130 PM update...

***beautiful afternoon in progress with low humidity***

Mostly sunny skies with just a bit of diurnal cumulus clouds will
allow highs to top out mainly in the lower to middle 80s. It will be
a few degrees cooler across the higher terrain and immediate coast
with very localized sea breezes...but still a beautiful day. Low
humidity and relatively light winds will make for a very comfortable
afternoon for outdoor activities.


Short term /6 PM this evening through 6 PM Saturday/... the high passes to our south...skies will be clear
with very light southwest winds. Overnight lows mainly in the
upper 50s to lower 60s.

Saturday...southern New England will be in a warm southwesterly
air flow between high pressure over the offshore waters and low
pressure advancing through the Great Lakes. Skies will be sunny to
start but with zonal flow aloft...some high level cloudiness will
move into the region in the afternoon. Dewpoints will still be in
the comfortable range...close to 60. Highs will be in the lower to
middle 80s. Late in the afternoon...a weak Lee-side trough will be
approaching the region from the southwest and this could be enough
to trigger a widely scattered shower or thunderstorm in western Massachusetts
and western CT.


Long term /Saturday night through Thursday/...
big picture...

Much of the upper flow remains unchanged through the forecast
period. Deep ridges will extend across western North America and the
western Atlantic. Closed low over northern Quebec anchors a trough
over eastern North America. Shortwave ejecting from the Pacific
northwest will plow over the top of the western ridge...then merge
with the eastern North America trough over the weekend. This will
deepen the trough and pull its features farther south. The trough
begins to eject north through eastern Canada by Thursday. The depth
of the trough and the extent of the ridges on either side will make
straight west-to-east movement difficult next week.

The mass fields and thermal fields of the GFS and European model (ecmwf) look similar
in overview. Some differences in details emerge during the first
half of next week. The similarity builds confidence in the overall
flow of the forecast. The longer range differences in detail support
using a blend of the forecast data.

The dailies...

Saturday night-Sunday... as the shortwave phases with the eastern
upper trough...the supporting upper jet extends east toward New
England. Meanwhile west to southwest low level winds 30 knots will
bring increasing humidity...which then rides over the surface
airmass. Isentropic field suggest the best lift will be over
northern New England. But low level wind fields vary from one model
to another. One feeds the low level jet toward northern New
England...a second toward Massachusetts...and the third toward Long
Island. In any of the scenarios...this will mean increasing clouds
and an increasing chance of showers/thunder overnight into Sunday as
the resulting warm front approaches. We will favor higher probability of precipitation to
our north but moderate confidence at best. Expect dewpoints to
increasing during this time and reach 65-70.

As we move into the warm sector on Sunday...the question will be how
much the airmass destabilizes. Model stability values suggest a fair
amount of energy to feed upon. Sb convective available potential energy climb above 1000 j/kg and
better than 60 percent chance of Li values less than -4. Precipitable
water values are squirrelly on the GFS but either side of 1.5
inches. This is well below 2 Standard confidence in heavy
downpours is low at this time. Winds at 500 mb are forecast around
40 knots. Overall...a concern for strong wind gusts in any
thunderstorms which will need to be monitored.


Upper shortwave moves into position along the trough axis over the
eastern Great Lakes. Strong upper jet leading the shortwave sets up
over New England with our area under the right entrance region
/favorable for generating lift/. Models hint at a wave developing
along the approaching cold front and providing an extra push to get
the cold front into New England. Instability remains with totals
upper 40s and around 50. Expect more showers/thunderstorms Monday...severe
potential will need to be monitored.

The cold front and supporting upper jet dynamics will still be in
the vicinity on Tuesday. The European model (ecmwf) holds the front over interior
southern New England while the GFS aims toward the east mass coast.
We will show chance probability of precipitation for most areas especially in the
afternoon...with precipitation pulling out to the northeast in the evening.

Wednesday-Thursday... upper trough remains in place with axis to our
west. The airmass dries with just a moist layer between 750 and 850
mb...which may contribute to periodic clouds especially during the
day. Surface high pressure builds into the region...which should
also work against any showers. Will go with dry weather in the


Aviation /18z Friday through Wednesday/...
forecaster confidence levels...

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

Short term /this afternoon through Saturday night/...high confidence
through Saturday evening. Moderate confidence late Saturday night.

This afternoon...VFR conditions with localized sea breezes.

Tonight and Saturday...VFR conditions other than very localized
patchy ground fog in the typically prone locations late
tonight/early Saturday morning. Southwest wind gusts of 20 to 25
knots are expected to develop along the eastern New England coast
Saturday afternoon.

Saturday night...VFR conditions during the evening. Some MVFR to
perhaps even localized IFR conditions may develop between 8z and
12z. In addition...we may see scattered showers and thunderstorms
move in to western New England between 8z and 12z.

Kbos taf...high confidence. Sea breezes should end between 20z and
22z as winds become south southwest. High confidence in no sea
breeze on Saturday with southwest wind gusts of 20 to 25 knots
expected during the afternoon.

Kbdl taf...high confidence.

Outlook...Sunday through Tuesday...moderate confidence.

VFR but with areas of MVFR in showers/tstms. Areas of IFR/LIFR in
late night/early morning fog especially along the South Coast.


forecaster confidence levels...

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

Short term /tonight through Friday night/...high confidence.

Today and tonight...excellent boating weather through tonight
with weak pressure gradient keeping winds/seas well below Small Craft Advisory
thresholds. Visibilities should be excellent most of the time.

Saturday...southwest winds will increase to 15-20 knots and may
gust to near 25 knots over the waters in the afternoon. A Small
Craft Advisory may be needed.

Outlook...Saturday night through Tuesday...moderate confidence.

Saturday night-Sunday...a warm front approaches the waters with
warmer more humid air and with clouds/showers/tstms. Increasing
southwest winds with gusts near 25 knots Sunday and seas build to
5-6 feet on the exposed waters. A Small Craft Advisory may be

Monday...warm humid air over the waters with
clouds/showers/thunderstorms. Southwest winds gusting 20 knots.
This should keep seas at near 5 feet on the exposed waters.
The potential for Small Craft Advisory will continue.

Tuesday...a cold front moves across the waters...but forecast models
differ on the timing of frontal passage. Continued chance of
showers/thunderstorms. Southwest winds diminish and turn west-
northwest after the front moves through. Seas remain around 5 feet
much of the day. Small Craft Advisory potential continues.


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


near term...Frank
short term...gaf
long term...wtb

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