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Area forecast discussion 
National Weather Service Taunton Massachusetts
340 PM EDT Tue Sep 27 2016

a front will stall just south of New England keeping the threat
of showers over Cape Cod and especially the islands through
tonight. A cool and unsettled pattern will persist into the
weekend, before slow improvement early next week.


Near term /until 6 am Wednesday morning/...
frontal boundary and assocd deep moisture axis just south of New
England and with upper level flow backing slightly tonight, the
front and moisture will remain in place for most of the night
before pushing south late as sfc ridging noses down from the
north. Models indicate decent mid level Omega south of new eng in
response to the convergence and right entrance region of upper jet
which will result in showers continuing tonight for Nantucket.
There is a fairly tight moisture gradient to the north which
should keep focus for rainfall over Nantucket, but may see a few
showers extend into Cape Cod and mvy. Rest of southern New England should be dry,
however there is a good set up for low clouds and areas of drizzle
developing late tonight as low level moisture expands south within
increasing low level NE flow and dry air aloft. Light winds will
become NE late tonight. Lows temps will remain mostly in the 50s


Short term /6 am Wednesday morning through Wednesday night/...
Wednesday into Wednesday night...
upper level low digs south from the Great Lakes which will result
in shortwave ridging aloft over new eng. This will maintain
surface ridging across the region from strong high pres over the
Maritimes. Synoptic forcing is weak which should limit shower
activity except perhaps across southeast new eng during Wed where deeper
moisture axis remains. Showers approaching from the SW Wed night
should remain to the west. Otherwise, increasing NE flow and
abundant low level moisture below dry air aloft will result in
patchy drizzle at times Wed into Wed night with widespread low
clouds. A cool raw day and night in southern New England with gusty NE winds to 30
mph along the coast. Highs Wed will be 60 to 65 degrees but only
upper 50s northern Massachusetts as wedge of low level cooler air noses down
from the north.


Long term /Thursday through Tuesday/...

* onshore flow brings cooler/wetter pattern through Saturday
* slow drying early next week
* keeping an eye on the tropics


Uncertainty remains high through weekend as we deal with cutoff low
moving through Ohio Valley and eventually across New England. While
12z models and their ensembles have come into better agreement with
its position and eventual track, the models often struggle with
details regarding timing of individual short waves around closed low
which affects how much rainfall we will eventually see.

Relying heavily on ensembles as opposed to individual model runs to
help Iron out uncertainty and run-to-run differences. Gefs and eps
probabilities both indicate greater potential for heavier rainfall
well to our southwest across mid Atlantic region where better jet
dynamics come into play as seen on 850/250 mb wind anomalies.

Presence of downstream ridging over New England combined with
persistent NE flow favors periods of rain/drizzle and patchy fog,
though forecast will indicate showers to help convey it won't be
raining all of the time. Does look like a period of steadier
rainfall will take place late Thu night into Fri and again late Fri
night into Sat as a couple of short waves rotate across region, so
bumped pops up to reflect this trend.

Drier air begins to work into region Sat night and especially sun as
cutoff low heads to eastern Great Lakes, before it weakens as tracks
across southern New England Mon along with surface cold front. High
pressure builds into northeast for midweek.

Beyond that, still way too early to say much on invest 97l. We're
sure many folks have seen longer range track guidance but we need to
caution against jumping on any one particular solution. Our advice
is to stay aware and informed over the next several days.


Aviation /19z Tuesday through Sunday/...
forecaster confidence levels.

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

Short term /through Wednesday night/...

High confidence on trends and overall theme. Lower confidence on
exact details.

Through tonight...MVFR/IFR conditions over the cape/islands will
eventually expand inland from east to west across southern New England later tonight
with patchy fog developing as well. CT valley will be last to see
lower clouds. Occasional showers will persist across ack tonight
with areas of drizzle developing elsewhere after midnight.

Wednesday and Wednesday night...widespread MVFR cigs likely with
pockets of IFR possible. Areas of drizzle. NE wind gusts to 25 kt
developing along the coast.

Kbos taf...overall high confidence in taf. Expect IFR cigs
developing later tonight into Wed with slight improvement
possible Wed afternoon.

Kbdl taf...moderate confidence in taf. Mainly MVFR cigs developing
late tonight into Wed.

Outlook /Thursday through Sunday/...moderate confidence.

Thursday through Saturday...periods of MVFR/IFR in areas of drizzle
and fog and possibly scattered heavier showers, especially near
coast. NE winds with gusts up to 30 kts at times.


forecaster confidence levels.

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

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

Tonight...winds shifting to light easterly tonight with increasing
NE winds across NE Massachusetts waters toward daybreak. Expect reduced
vsbys with scattered showers and patchy fog, mainly southeast waters.

Wednesday and Wednesday night...increasing NE winds with gusts
25-30 kt developing, strongest on the eastern waters. Small Craft Advisory for all
waters. Seas building up to 7-9 ft eastern waters. Patchy drizzle
and fog will reduce vsbys at times.

Outlook /Thursday through Sunday/...moderate confidence.

Small Craft Advisory conditions likely through at least Saturday due
to persistent NE flow. Gusts could reach gale force at times,
especially later Thu night and Fri. As a result, seas should build
to 8 to 10 ft offshore, possibly up to 12 ft. Also expect areas of
drizzle and fog with scattered heavier showers, reducing visibility
to around 1 nm at times.

Winds diminish later Sat into sun but seas offshore should take
longer to subside.


Box watches/warnings/advisories...
Rhode Island...none.
Marine...Small Craft Advisory from 8 am Wednesday to 8 am EDT Thursday
for anz230>237-254>256.
Small Craft Advisory from 5 am Wednesday to 8 am EDT Thursday
for anz250-251.


near term...kjc
short term...kjc
long term...jwd

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