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Area forecast discussion 
National Weather Service Taunton Massachusetts
501 am EDT Tuesday Sep 23 2014

Synopsis...
high pressure will bring dry weather along with mild days and
cool nights through Wednesday. Coastal low pressure well south of
the region may graze south coastal areas with a low risk for few
showers Thursday afternoon into Friday morning. High pressure
returns Friday into early next week with dry weather and
unseasonably warm afternoons. It is possible a few record high
temperatures may be challenged this weekend.

&&

Near term /until 6 PM this evening/...
cancelled the frost advisory early. Low level dry air did not
arrive quickly enough to permit widespread areas of frost. There
were a few spots in southern New Hampshire and northwest Massachusetts which are close
to the frost formation temperatures already this morning. So we
cannot completely rule out at least some frost this morning.

Today...
high pressure crests across southern New England. This means
mostly sunny skies and a predominantly light west wind. Some of
the high resolution guidance is hinting at a seabreeze developing
along the coast this afternoon. The latest runs of the rap...along
with both cores of the hi-res NAM do decrease winds where a
seabreeze would be possible...but keep the boundary just off the
East Coast. The only model/guidance source which has consistently
developed a seabreeze is the hrrr.

Like the previous forecaster...am wary about the possibility of a
seabreeze developing. With the high pressure arriving later in the
day...am thinking the offshore pressure gradient should remain
just strong enough to hold it offshore...but it will be something
which will need to be watched.

&&

Short term /6 PM this evening through 6 PM Wednesday/...
Tuesday night...
high pressure builds to the north with a continuation of clear
skies and a light NE wind developing overnight. We used a blend of
the guidance which yields min temperatures mostly in the 40s. Went
higher along the East Coast of Massachusetts as well as the larger urban
centers.

Wednesday...
large high pressure centered over northern New England will
result in dry/pleasant weather for late September. Given the
positioning of this high pressure...still expecting easterly
winds at the surface. So lowest temperatures will be found near
the eastern Massachusetts coast. Highs should range from mainly the 60s...to
perhaps near 70 in the lower CT River Valley.

&&

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

* low risk of a few showers near the South Coast Thursday into Friday
morning
* unseasonably warm afternoons this weekend
* dry with no appreciable rainfall in sight

Overview and model preferences...

Medium range operational models start off in pretty good
agreement...then having difficulties resolving low pressure off the
middle Atlantic coast and its possible shift to the north sometime during the
Thursday into Friday timeframe. Question is whether east-west oriented
ridge axis across central New England lifts far enough north to allow
moisture to work into at least southern portions of the region.
Due to the differences...used a blend of available guidance and
ensembles to incorporate wide range of possibilities...though
leaned toward a drier solution.

Beyond this...model trends continue to show high amplitude 500 mb ridge
centered across the central U.S. With main storm track across Hudson
Bay through most of the week. Noting a 500 mb short wave in this flow
during next weekend...with ridging possibly retrograding to the
plains states while the short wave works into the Gulf of St.
Lawrence and southern tip of Greenland. Have noted that the CPC nao
guidance currently has positive nao that starts to trend more
negative toward the end of the month...around the timeframe of this
short wave. 500 mb heights may lower next weekend...with a possible cold
front trying to shift S out of Quebec.

Toward the end of the forecast...continued to use a blend of
available guidance into the weekend...then trended toward the
ensemble means.

Details...

Wednesday night...

East-West Ridge axis remains close to the Massachusetts/NH/VT border during the
night with general east-southeast wind flow in place. Question at this point
will whether moisture starts to work north from low pressure near the
Delaware-Maryland-Virginia peninsula. Models having a very difficult time handling
this feature...though 00z GFS/ggem are more aggressive in breaking
down the ridge and pushing precipitation in...while 00z European model (ecmwf) holds
precipitation to the S. Leaned more toward the drier solution and holding
the ridge in. Do increase the clouds during the night though.
Expect overnight lows mainly in the 40s...though holding in the
Lower-Middle 50s along the immediate coast.

Thursday through Friday...

Continue to keep a weary eye on the persistent low pressure near the
Delaware-Maryland-Virginia peninsula during this timeframe. GFS/ggem remain
aggressive in bringing good slug of precipitation across the region
during this timeframe. With this run...the ec is also bringing
some precipitation in across southern areas...but keeping heaviest quantitative precipitation forecast to
the S. All models keep the low rather weak and near or S of 40n
latitude. Agree with previous forecast...with a rather weak upper
flow in place will be tough to bring appreciable precipitation into the
region.

Another aspect to consider will be the possibility of increasing
east to NE winds with broad inverted trough that may develop as the
low passes. For now...kept strongest winds mainly over the coastal
waters...but could also shift north with the precipitation.

Did bring slight chance probability of precipitation into north CT/RI/se Massachusetts for now...but
again will need to monitor the progress of this system.

With the cool onshore flow...expect highs only in the 60s to
around 70 on Thursday...though could warm to the Lower-Middle 70s
away from the coast on Friday depending upon when the low passes
and winds back to a light northerly direction. Lows Thursday night will
range from the middle 40s well inland to the middle-upper 50s along the
shore.

Friday night through Monday...

High amplitude 500 mb ridge remains across the eastern and central
U.S. Through most of this period. Expect dry conditions with mild
temperatures especially during the weekend. May see record highs
on Saturday and/or Sunday. Models try to lower 500 mb heights across
central and southern Quebec into the region during Monday along
with a cold front...but timing is in question. Did hold temperatures back
a bit for now...mainly in the 70s.

Only question will be on Monday...as models try to push a cold
front out of Quebec toward the region. Timing is in question
though.

Record high temperatures this weekend into next Monday...

Sat 9/27... sun 9/28... Monday 9/29...

Bos...86...1998 bos...90...1881 bos...88...1952
bdl...88...1998 bdl...83...1959 bdl...86...1945
pvd...86...1998 pvd...84...1943 pvd...87...1945
orh...85...1933 orh...84...1916 orh...84...1952

&&

Aviation /09z 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/...

High confidence VFR. Low probability of a seabreeze this
afternoon.

Kbos terminal...high confidence. Low probability of a seabreeze
this afternoon.

Kbdl terminal...high confidence.

Outlook...Wednesday night through Saturday...

High confidence in VFR conditions through the period. May see
typical brief late night/early morning patchy ground fog in the
typically prone locales.

There is a low risk for a brief period of MVFR conditions near the
South Coast...cape and islands late Wednesday night into Friday morning.
This will depend upon whether a few showers can make it into
that portion of the region with offshore low pressure.

&&

Marine...
forecaster confidence levels...

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

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

Winds and seas continue to diminish across all coastal waters
today as high pressure moves in. Made some tweaks to timing of
small craft advisories this morning based on observed trends.
Rather tranquil boating conditions expected through Wednesday.
Seas may build above 5 feet across the southern outer coastal
waters late Wednesday...but the timing is not certain.

Outlook...Wednesday night through Saturday...

Wednesday night...high confidence. Winds and seas below small
craft...though may begin to build late Wednesday night on southern
outer waters.

Thursday through Friday...moderate confidence. Low pressure will pass
S of the 40n/70w benchmark late Thursday night or Friday morning. Looks
like east to NE winds will gust up to 25 knots mainly on the outer
waters from east of Cape Cod to the southern waters. Swells may build
up to 6-8 feet. This is dependent upon how far north the low will push
before moving offshore.

Friday night-Saturday...high confidence. Winds back to north and
diminish. Leftover seas of around 5 feet Friday night should subside.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory until 7 am EDT this morning for anz250.
Small Craft Advisory until 11 am EDT this morning for
anz254>256.

&&

$$
Synopsis...Belk/evt
near term...Belk
short term...Belk
long term...evt
aviation...Belk/evt
marine...Belk/evt

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