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Area forecast discussion 
National Weather Service Taunton Massachusetts
1026 PM EST Sat Dec 27 2014

Synopsis...
a cold front over the Saint Lawrence valley this evening will move
across southern New England Sunday...bringing rain showers.
Canadian high pressure then builds over the northeast USA and
brings colder weather for much of the week.

&&

Near term /until 6 am Sunday morning/...
1025 PM update...have adjusted temperatures downward since they
are now below 32 in a few spots in northwest Massachusetts and in the middle 30s at
Chicopee...Fitchburg...Norwood...Willimantic...and on Marthas
Vineyard.

Light sprinkles seen on radar in eastern New York were evaporating
before reaching southern New England. Thus have higher confidence
that the onset of precipitation will be a few hours later than in
our grids. With increasing cloud cover and a light southerly wind
flow...am expecting that temperatures will have risen just enough
to prevent any freezing rain at the onset. However...will be
monitoring this closely overnight.

Remainder of previous discussion...
low pressure in the Great Lakes will pass north of New England
later tonight. In the process it will swing a cold front into
northern and western New England toward morning. We are expecting
a few showers out ahead of this front late tonight with the best
chance in the hills west of the CT river.

&&

Short term /6 am Sunday morning through Sunday night/...
overview...trough digs over the western USA making room for cold
air to move south into the western USA. Shortwave north of the
Great Lakes moves east...with the shortwave axis crossing New
England Sunday night. The upper flow remains generally westerly
through the period.

Sunday...cold front moves across southern New England Sunday.
Model cross sections show deep moisture during the day with
precipitable water values briefly rising to around 1 inch. There
is sufficient lift and moisture to support showers. We have bumped
probability of precipitation up to 50-60 percent. Behind the front...winds shift to west-
northwest. Vertical profiles suggest potential mixing of 20 knot
winds to the surface in gusts. Temperatures in the mixed layer would
support maximum surface temperatures in the 40s...maybe around 50 along the
South Coast. Depending on how fast the colder air moves in it is
possible that extreme northwest mass may stay in the 30s.

Sunday night...the last of the showers should move south of the
South Coast and islands. Drier air will mean a clearing trend
overnight. With dewpoints in the 20s and light northwest
winds...expect temperatures away from the coast to dip below freezing.

&&

Long term /Monday through Saturday/...
highlights...
* dry weather through most of the work week
* seasonable to perhaps slightly below normal temperatures expected
* next shot of precipitation potentially late Friday into Saturday

Models are in good agreement through much of the long term with
northerly flow and cooler temperatures to start the week off.
General flow shifts to the southwest as low pressure moves over
Hudson Bay with moderating temperatures expected Wednesday and
Thursday. Models start to show some timing discrepancies for Friday
into the weekend with the GFS a bit faster than the European model (ecmwf) with a low
pressure system moving through Quebec and into the Maritimes. The
GFS also hints at a secondary low developing over the tri-state area
during this period. Whether or not this occurs will affect
temperature profiles as well as locations and amounts of
precipitation. At this point...will use a blend of the models for
this time period while the next few runs shake out.

Monday and Tuesday...dry but more seasonable weather is expected as
high pressure builds into the Great Lakes and surface winds allow
colder air to drain from the north.

Wednesday and Thursday...winds shift to the southwest as low
pressure moves over Hudson Bay and then eastward through Quebec.
While there is a cold front associated with the low...models are
forecasting this to stay well to our north at this time.
Therefore...dry weather will persist but temperatures will moderate
a bit.

Friday and Saturday...as stated above this is the period of greatest
uncertainty. There are both timing and track differences between
the European model (ecmwf) and the GFS. A low pressure system and/or cold front will
affect southern New England during this time period...bringing a
decent round of precipitation to the region. As the models are
inconsistent with the track of the storm...it is too early to tell
whether this will be more of a wintry precipitation or rain.

&&

Aviation /03z Sunday through Thursday/...
forecaster confidence levels...

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

Overnight...high confidence. Mainly VFR. Increasing clouds from
west to east after midnight. Low probability of MVFR ceilings/local
MVFR visibilities in scattered showers across western Massachusetts and northwest CT well
after midnight.

Sunday...high confidence. Generally VFR but with MVFR ceilings
and visibilities possible in any rain showers. SW winds 10 to 20 knots
shifting to the northwest.

Sunday night...high confidence. VFR with a light northwest wind.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook...Monday through Thursday...

Monday and Tuesday...high confidence. VFR.

Wednesday and Thursday...moderate confidence. VFR.

&&

Marine...
forecaster confidence levels...

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

Short term /through Sunday/...moderate to high confidence.

Overnight...cold front approaches from the Great Lakes and
reaches western New England toward morning. Winds will increase
from the southwest with gusts near 25 knots possible by daybreak.

Sunday...cold front moves across New England during the morning
and across the waters during the afternoon. Southwest winds become
west with frequent gusts to 25 knots...and seas build to around 5
feet on the outer waters. Winds and seas diminish toward evening.
A Small Craft Advisory is in effect for most of the waters for
Sunday.

Sunday night...winds and seas diminish. Seas may linger near 5
feet on the outer portions of the outer waters overnight.

Outlook...Monday through Thursday...

Monday through Wednesday...high confidence. Quiet boating conditions
expected. Northerly winds Monday will shift to the southwest and
west Tuesday and Wednesday.

Thursday...moderate confidence. Seas start to build as high
pressure moves away from the waters. Westerly winds increase with
low pressure over the Great Lakes and high pressure moving off the
middle- Atlantic. Small craft conditions are possible during this
time frame.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 6 am to 6 PM EST Sunday for anz232-
235-237-250-254>256.

&&

$$
Synopsis...wtb/rlg
near term...wtb/gaf
short term...wtb
long term...rlg
aviation...wtb/rlg/gaf
marine...wtb/rlg/gaf

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