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Area forecast discussion 
National Weather Service Taunton Massachusetts
709 PM EDT Tuesday Sep 30 2014

Synopsis...
cool damp conditions remain in place into Thursday...with more
widespread rainfall expected tomorrow. Dry weather returns later
Thursday into Friday as high pressure builds back across the
region. A cold front with associated low pressure will likely
bring a period of rain Saturday followed by cooler and drier
conditions for Sunday into Monday.

&&

Near term /until 6 am Wednesday morning/...
7 PM update...
area of light rain is diminishing across southern New England as WV loop shows
deeper moisture moving off to the east. However...given all the
north-NE flow off the cool Gulf of Maine...will likely see areas of
drizzle and patchy fog develop through this evening.

Middle level low spinning near Lake Erie with associated cold pool
helping to trigger convection across central PA and West New York.
Instability is expected to diminish tonight so thunder not
anticipated for southern New England...but we expect rain to expand across the
region overnight as the middle level low approaches southern New England from the
west and middle level Omega increases along with deepening moisture.

Previous discussion...
through the early morning hours however...expect inverted trough
between the offshore low pressure and the east moving Upper Cutoff to
begin to enhance. Note increase in baroclinicity and deformation
across the area through the morning...which combined with
deepening moisture from the surface to h4 or so...suspect increase in
more widespread rainfall across southern New England during the early
morning hours...such that it/S likely raining at over much of the
box County Warning Area by 12z.

&&

Short term /6 am Wednesday morning through Wednesday night/...
tomorrow...
as mentioned above...as upper level cutoff shifts almost directly
overhead and low pressure continues well to the southeast of the
benchmark...a moderate inverted trough is likely to continue to
develop through the morning and into the afternoon. This provides
better f-general and even a deformation axis for deeper lift across
the area. This is also combined with modest Ely low level jet with wind
speeds at 850 mb around 25-30 knots /2+ Standard deviations above normal/
and precipitable waters to around 1.5 inches which is 1-2 Standard deviations above
normal for early October. Therefore...expect more widespread
rainfall across most of southern New England through the day...its not
until the surface ocean system pulls east late in the day that the
moisture begins to decrease. Many areas may receive some of the
steady soaking rainfall they have needed for some time now with
the possibility of rainfall amounts ranging 0.25-0.75 inches.
Pockets of heavier rain are also possible given the banding
potential which may be enhanced thanks to k-values in the low
30s...but it/S difficult to say exactly where this will set up. So
will at least highlight the potential for some localized areas of
1.0+ inches. For now...the best chance looks like southeast Massachusetts...where
the inverted trough holds in the longest...but it/S not out of the
question it is observed inland...especially where an east component
to the flow enhances upslope.

Other than the rainfall...cool temperatures are expected as many
locations remain in the upper 50s to around 60 degrees.

Tomorrow night...
rainfall will slowly come to an end from west to east through the
evening...possibly lingering across Rhode Island and southeast Massachusetts into the early
morning hours. However...with east component to the flow...and low
level moisture remaining in place...expect another chance for fog
and drizzle at times through the overnight hours. Min temperatures remain
likely in the 50s.

&&

Long term /Thursday through Tuesday/...
highlights...

* sunshine and light winds Friday
* rain likely Saturday
* cooler and mainly dry weather Sunday into Monday
* more showers possible Tuesday

Overview...
medium range deterministic and ensemble guidance in general
agreement on the large scale pattern during the extended period. Middle
level low exits the region toward the end of the week...then main
feature will be an anomalous middle level trough/low digging into the
upper Midwest and western Great Lakes by Sat. A piece of energy
rotating around the middle level low will bring a frontal system into
new eng late Sat/Sat night which will be accompanied by a period of
rain which may be locally heavy...but exact timing is uncertain.
After shortwave exits...broad trough will remain across southern
Canada and Great Lakes Sunday into early next week with next shortwave
and front approaching next Tuesday. There are also timing
differences with this front as the GFS is more progressive than the
European model (ecmwf) which will affect timing of potential showers early next week.

Dailies...

Thursday...
middle level low will gradually pull away from southeast new eng as high pressure
builds into the region. Cross sections suggest mostly cloudy skies during
the morning and cant rule out a few showers near the coast in
persistent cyclonic flow...then becoming ptsunny from west to east
in the afternoon as drier air moves in. With NE flow... temperatures will
hold in the 60s.

Friday...
southern New England will be in between systems with high pressure overhead leading to
mosunny skies and light winds. Will have to watch clouds backing in
from the ocean associated with offshore storm which may bring more
clouds to the Outer Cape. GFS and NAM are suggesting this increased
cloud cover while European model (ecmwf) keeps clouds to the east. With continued
onshore flow temperatures expected to be in the 60s...coolest east Massachusetts coast.

Saturday into Saturday night...
models are in good agreement on timing of cold front into southern New England late
Sat into Sat night. Decent low level jet and anomalous precipitable water plume
ahead of the front will bring a period of rain to southern New England which may be
locally heavy...but this system is fairly progressive. Timing is
still uncertain but it appears bulk of rain will fall during
Sat...which may linger into Sat evening across east new eng.

Sunday...
front is offshore Sunday with dry westerly flow which will lead to
sunshine and blustery conditions. 850 mb temperatures below normal and will
lead to below normal temperatures Sunday.

Monday and Tuesday...
next front approaches from the west but there are differences in
timing and amplitude of the shortwave and how progressive the front
will be. Even faster GFS is mainly dry for Monday so we are going with
a dry forecast for now. The main uncertainty is with Tuesday as
progressive GFS moves the showers offshore while more amplified
European model (ecmwf) is wet.

&&

Aviation /00z Wednesday through Sunday/...
forecaster confidence levels...

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

Short term...high confidence on trends but lower confidence in
timing.

Through tonight...
mainly IFR east of an ijd-orh-mht line...with MVFR west. This is
mainly due to ceilings through evening...but visibilities may begin to dip
as well tonight in a mix of drizzle/fog/light rain. Possibility
of periodic IFR visibilities. Ceilings remain low...but visibilities lift during
the morning hours as rain becomes more widespread and allows visibilities
to lift to mainly MVFR/VFR. Winds pick up near shore in the
east...with a few gusts approaching 20 knots at coastal terminals.

Tomorrow and tomorrow night....
much of the same...mainly IFR/MVFR ceilings with some MVFR conditions
in rain. Expect a very slow improvement from west to east late in the
day and overnight...but this will be mainly toward rain
ending...with categories only really improving during the daylight
hours on Thursday.

Kbos...high confidence on trends...lower confidence on timing.
Also low confidence of a brief period of LIFR conditions possible
during the overnight hours before improvement in the morning.

Kbdl...high confidence on trends...lower confidence on timing.

Outlook...Thursday through Sunday...

Thursday...moderate confidence. Areas of IFR in the morning should
improve to VFR in the afternoon as ceilings lift and clouds break up.

Friday...high confidence. VFR.

Sat...moderate confidence. Conditions lowering to MVFR/IFR as
showers move into the region. Lower confidence on timing. Gusty
southerly winds possible ahead of a cold front shifting to west Sat
night.

Sun...moderate confidence. VFR.

&&

Marine...
forecaster confidence levels...

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

Short term...high confidence through tomorrow night.

North-NE flow will gradually increase through the early morning hours
into tomorrow...with wind gusts around 25 knots at times possible
particularly by tomorrow afternoon and overnight. Small craft
advisories have been issued for the ocean waters as well as Rhode Island/bi
sound for these winds...and may need to be added for the waters
surrounding Cape Cod for late in the day tomorrow.

Otherwise...Small Craft Advisory conditions are likely due to
increasing swell alone...which has the potential to reach 7-8ft
by tomorrow afternoon on the ocean waters. It/S likely that these
small craft advisories will need to linger into Thursday.

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

Thursday into Friday...expect NE wind gusts to 25-30 knots Thursday morning over southeast
waters which will gradually diminish Thursday afternoon and night.
Continued NE winds Friday but speeds less than Small Craft Advisory. Hazardous sea
conditions expected Thursday into Friday over outer waters.

Sat...southerly winds developing ahead of a cold front with gusts
increasing to 25-30 knots. Winds shifting to west during Sat night.
Hazardous sea conditions continue over outer waters. Visibilities may be
reduced in showers and fog.

Sun...west winds may gust to 25-30 knots in Post frontal airmass.
Hazardous seas continue over outer waters.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
New Hampshire...none.
Rhode Island...none.
Marine...Small Craft Advisory from 2 am Wednesday to 8 am EDT Thursday
for anz235-237.
Small Craft Advisory until 8 am EDT Thursday for anz250-251.
Small Craft Advisory from 10 PM this evening to 8 am EDT
Thursday for anz254>256.

&&

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

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