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Area forecast discussion 
National Weather Service Taunton Massachusetts
149 PM EDT Friday Aug 22 2014

Synopsis...
the threat for showers will continue...especially across the west
through tonight. Drier and cooler weather follows this weekend. A
warm-up is possible next week prior to an unsettled pattern ahead
of a frontal boundary sweeping south out of Canada.

&&

Near term /until 6 PM this evening/...
145 PM update...
area of slow moving showers has developed across CT valley in northwest
Massachusetts and SW New Hampshire with second area persisting over the ocean to the
south. Also still a few isolated showers popping up in Rhode Island and NE Massachusetts.
Main focus for showers into this evening will be across west new
eng...but cant rule out a brief shower elsewhere as weak impulses
rotate southward into the region. Adjusted probability of precipitation slightly...otherwise
forecast on track.

Previous discussion...
middle level trough axis hanging across northern new eng with weak
impulses rotating around the trough. Morning shower activity has
decreased in coverage with just a few showers remaining over the
Outer Cape and southeast Massachusetts. Hi res guidance indicating main focus for
additional showers this afternoon will be across west new eng where
deeper moisture exists. No surface instability to speak of as southern New England
remains under influence of maritime airmass with high pressure nosing
down from east Canada. Instability axis will remain well to the west.
It will be a cool day under the cloud cover with temperatures remaining
mostly in the 60s in the interior...but low 70s in the lower CT
valley and portions of Rhode Island/southeast Massachusetts where some thinning of cloud cover
possible.

&&

Short term /6 PM this evening through 6 PM Saturday/...
tonight...
am noting similar setup as Thursday night. Another weak shortwave will
push north-S across the region and phase with offshore longwave trough
connected to cutoff in Atlantic Canada. Two conditions are
different however...precipitable waters are a bit lower /1.0-1.25 inches as
opposed to 1.5/ and k index values are lower as drier air intrudes
through the column from the top down. Therefore...save for the
advection of leftover convection from the west...suspect that -shra
are likely to be a bit weaker and less widespread than Thursday night.
However...will still maintain at least chance probability of precipitation especially for
west and northwest portions of the forecast area.

One other issue is fog and/or low ceilings moving into east portions of
the forecast area. Guidance continues to note an area of moisture
backing in from the Gulf of Maine overnight thanks to continued
Ely component of the flow. Do note in BUFKIT profiles that there
is a layer of dry air above the surface which may negate fog
development...especially if stratus backs in...limiting radiative
processes. Therefore...will mainly mention low clouds...but may
need to monitor for drizzle with drier moving in over moisture
pooling in the low-middle levels. Should some areas radiate...fog
remains a risk.

Sat...
one last parting shot for showers Sat as shortwave energy forces
some digging and southward progression of the offshore longwave
trough. Leftover moisture combined with cooling temperatures aloft are
likely to lead to a fair amount of cloud cover during the early
half of the day...along with showers especially from portions of
the Merrimack valley east and points southeast. However...improvement by the
afternoon looks possible thanks to gradually rising heights from
the S shift in the trough. This will allow surface inverted ridging to
gradually regain control across the region toward evening. In
fact...despite the cloudy start to the day...its possible many
locations still get to see the sunset /even in the east which will
likely take the longest to break out/. Highs remain on the cool
side of normal thanks to the early cloud cover limiting diurnal
influence.

&&

Long term /Saturday night through Thursday/...
highlights...

* quiet weather expected through much of this period
* uncertainty increases middle of next week with an approaching
front

21/00z models are in good agreement through about Tuesday. Then
significant differences arise for the latter half of next week...
making for a lower confidence forecast from the middle of next week
Onward.

A persistent upper level trough over the northeast will slowly make
its way east...moving just offshore this weekend as an upper level
ridge tries to push northeastward from the southern USA. This upper
trough is rather persistent though...with each successive model run
lingering this trough over the North Atlantic longer and longer.

Cooler...less seasonable weather is expected while high pressure in
Quebec will keep things relatively dry. Still agree with the
previous forecaster...thinking 21/00z guidance continues to struggle
with convective feedback into early next week. As such...kept a dry
forecast across most of southern New England.

A high pressure will sink south into early next week...eventually
moving south and east of southern New England and returning US to a
more westerly flow. A low pressure in Ontario may eventually move
east into Quebec...swinging a cold front through southern New
England Wednesday or Thursday. This is where models start to diverge
more significantly.

The European model (ecmwf) looks a bit quicker than the GFS with the approach of this
front...but neither is as progressive as the Canadian. Will take a
blended approach with the timing for now. Given the strength of the
surface ridge expected to be near the coast...would not be overly
surprised if the ultimate timing turns out to be slower than the
GFS. Depending on available moisture...we could see some showers and
thunderstorms ahead of this front.

&&

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...through Saturday night...moderate confidence.

Through tonight...conditions have improved to VFR across much of
the region...but expect lowering ceilings back to MVFR/IFR tonight.
Scattered showers lingering into the evening...especially west. We are
fairly confident in this trend but timing is less certain. We also
have lower confidence on extent of fog development tonight. At
this time...best chance for fog appears to be in the CT valley.

Saturday...conditions improve to VFR by midday with at least
partial clearing developing during the afternoon from the north
and east. A few showers still possible...mainly northwest.

Saturday night...mainly VFR...but patchy late night fog
developing in normal fog prone locations.

Kbos terminal...moderate confidence. Expect ceilings to lower to MVFR
this evening. Timing uncertain and could be a few hours earlier or
later than forecast indicates.

Kbdl terminal...moderate confidence. Expect ceilings to lower to MVFR
tonight. Timing uncertain and could be a few hours earlier or
later than forecast indicates.

Outlook...Sunday through Tuesday...

High confidence VFR. Low probability of patchy MVFR/IFR fog each
night.

&&

Marine...
forecaster confidence levels...

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

Short-term...through Saturday...high confidence.

East to NE flow will continue into Sat as high pressure to the NE slowly
regains control. Through the day today and night tonight...periods
of wind gusts of 15-20 knots are possible at times with a slowly
building swell. Seas should remain below 4 feet even on the southeast and S
waters. Therefore...no small craft headlines. Some fog and showers
are possible on the waters at times as well...mainly this
morning...and once again overnight.

Outlook...Saturday night through Tuesday...

High confidence.

High confidence. Quiet boating weather is expected for much of this
period with high pressure across the region. Seas could approach 5
feet across the outermost southern coastal waters this weekend. Not
enough confidence to issue a Small Craft Advisory though. Low
probability of patchy overnight fog limiting visibilities.

&&

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

&&

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

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