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Area forecast discussion 
National Weather Service Taunton Massachusetts
654 PM EDT Wednesday Sep 17 2014

Synopsis...
high pressure will keep conditions cool and dry tonight. A weak
cold front will cross the area on Thursday...but moisture
associated with the front is limited. Cold high pressure builds
into the area during Thursday night and Friday. Some frost is
possible early Friday morning in some areas. The high will then
slip offshore and southwest flow behind it will allow temperatures
to warm to near or above normal Sunday and Monday. A cold front
moves through on Monday...followed by cooler weather Tuesday and
Wednesday.

&&

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

7 PM update...
high pressure shifts offshore while maintaining clear skies and
dry conditions over southern New England for much of tonight.

A weak cold front moves across from the St Lawrence Valley and
eastern Great Lakes. The portion of this front upstream of our
area has limited moisture...so at most we expect an increase of
clouds after 2 am mostly in western mass/southern New Hampshire.

Near calm winds should allow for good radiational cooling with
temperatures falling into the 40s away from the coast and in traditional
cold spots such as Marthas Vineyard Airport. Remaining locations
will have temperatures in the low to middle 50s. Patchy valley fog is
possible.

&&

Short term /6 am Thursday morning through Thursday night/...
Thursday...
the cold front will move through southern New England
during the day...with winds shifting to the northwest. Models
continue to show minimal moisture associated with this front as it
crosses through our area. Will likely see increasing clouds with
diurnal cumulus...can/T rule out an isolated shower or two but with
precipitable water under an inch any rain amount would be light and
likely brief. Main concern with the front will be ushering in
cooler temperatures.

Thursday night...
potential for the coolest portion of the forecast. With the
cold front southeast of the area...clearing is expected in the
evening...with cold high pressure building over the area. Dewpoints
should fall into the 30s...so assuming clearing occurs quickly
enough with radiational cooling...temperatures could fall into the middle
30s in northwest Massachusetts/SW New Hampshire valleys which may require frost advisories.
Elsewhere...still a cool morning Friday...upper 30s and low 40s
possible.

&&

Long term /Friday through Wednesday/...
big picture... zonal flow Friday with 500 mb heights building from a
little below normal to a little above by the nighttime. Upper ridge
builds over the western states while a shortwave in the flow digs
over the northern plains and Great Lakes over the weekend. The
trough then moves over New England early next week.

Best chance of showers would be Sunday night-Monday as the trough
approaches. Expect a warming trend over the weekend followed by
cooling temperatures early next week as the trough moves overhead.

The dailies...

Friday-Saturday-Sunday... high pressure centered over northern New
England Friday moves east over the Maritimes during the weekend. The
ridge axis holds across southern New England into Saturday...then
shifts south Sunday. This should support dry weather through the
period. The European model (ecmwf) actually brings showers into our northwest areas
Saturday night and then again Sunday afternoon. But both GFS and
European model (ecmwf) show a similar jet position entering the St Lawrence
Valley...and the GFS is dry until Sunday night. Added to this is the
overall dry pattern for southern New England the past few weeks and
which favors the drier forecast.

Temperatures at the top of the mixed layer are forecast equiv to a temperature of
0-1c at 850 mb Friday...warming to 10-11c by Sunday. This supports
maximum surface temperatures upper 50s-lower 60s Friday...warming to 75-80 Sunday.
Winds in the mixed layer are forecast to reach near 20 knots
Saturday and 25 knots Sunday. We have bumped up the model grids to
reflect these values.

Sunday night-Monday... upper shortwave moves into the Great Lakes
and swings a cold front through southern New England late Sunday
night or Monday morning. The European model (ecmwf) is a little faster with
frontal passage...but we stayed closer to the GFS. Much of the system remains
to our north but southern New England remains in the right entrance
region of the supporting upper jet which should promote some lift.
We will hold with chance probability of precipitation for showers overnight and Monday.

Tuesday-Wednesday... upper trough and cold pool move overhead
Tuesday and east of US Wednesday. Surface high pressure builds in
both days. Enough destabilizing aloft and cloud-level moisture to
support diurnal clouds Tuesday. Otherwise fair weather both days.
Temperatures in the mixed layer support maximum surface temperatures in the 60s both days.
Dew points in the upper 30s and 40s will support min surface temperatures in
the 40s...possibly some upper 30s.

&&

Aviation /00z Thursday through Monday/...
forecaster confidence levels...

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

Short-term /through Thursday night/...high confidence.

Tonight and Thursday...high confidence. VFR conditions expected
across the area. Scattered areas of IFR ceilings/visibilities in patchy
fog/stratus late tonight over the far interior. Very isolated
showers possible during Thursday...any rain should be light with
probable VFR conditions with the light showers.

Thursday night...high confidence. VFR conditions expected.

Kbos terminal...high confidence in taf tonight with VFR
conditions through Wednesday. Moderate confidence in northwest winds on Wednesday
becoming east/NE during the PM.

Kbdl terminal...high confidence in taf.

Outlook...Friday through Monday...moderate to high confidence.

VFR through the period. Patchy IFR ceilings/visibilities in fog Saturday and
Sunday early mornings. Patchy MVFR in showers Sunday night and
Monday. Southwest winds Saturday may gust to 20 knots. Southwest
winds Sunday may gust 25 knots...possibly a little higher.

&&

Marine...
forecaster confidence levels...

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

Short-term /through Thursday night/...moderate confidence.

Tonight and Thursday... swell from Hurricane Edouard will slowly
build into the coastal waters with increasing seas. There is a
possibility that seas may approach 5 feet on the outer coastal
waters for a few hours Thursday morning. However...confidence in
this not high enough at this time to Post headlines.

Thursday night...the potential exists for 5 foot seas on the
outer coastal waters Thursday night...and with cold air advection
behind the cold front Thursday night some gusts in the low 20 knots
range are possible on the outer coastal waters as well. Small
craft advisories may be needed for seas starting Thursday night.

Outlook...Friday through Monday...moderate confidence.

Friday...diminishing northeast to east wind less than 20 knots.
There will be some 5 foot seas on the eastern waters Friday morning
supported by a 2-3 foot southeast swell...but this will subside
through the day. Small Craft Advisory for seas may be needed for
part of Friday.

Saturday-Sunday...winds swing around to southwest with daytime gusts
around 20 knots...possibly near 25 knots Sunday. Seas will remain
2-4 feet. A cold front approaches late Sunday with a chance of
showers Sunday night.

Monday... a cold front crosses the waters early in the day. West
winds behind the front will remain less than 20 knots. Seas will
build to 5-7 feet on the outer and exposed waters...as a south swell
increases to 3-5 feet.

&&

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

&&

$$
Synopsis...wtb/nmb
near term...wtb/nmb
short term...nmb
long term...wtb
aviation...wtb/nmb
marine...wtb/nmb

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