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Area forecast discussion
National Weather Service Taunton Massachusetts
204 PM EST Fri Dec 9 2016

Synopsis...

* near- and short-term forecast updates only...

Mainly dry, but unseasonably cold temperatures are on tap for our
region through Saturday. Some mixed wintry precipitation is looking
more likely Sunday evening into the day on Monday, but uncertainty
remains. Cooler conditions return by the middle of next week.

&&

Near term /through tonight/...

Rest of today...

Northwest winds persisting with gusts up to 35 mph beneath a deck of
scattered cumulus, subsequent of deep layer mixing of residual
moisture and fetch off the Great Lakes region. Also seeing some
flurry activity get as far east as western and central portions of
southern New England, but given how dry the atmospheric column is,
only expect flurries across the east slopes of the Berkshires into
the CT River Valley. Low risk of accumulation and/or visibility
restrictions. Temperatures lowering back down to the 20s towards
sunset. Couple the winds, going to feel 10 degrees colder. Only
193 days left till Summer!

Tonight...

Northwest flow continues but beginning to relax as surface high pressure
builds in from the west coincident with weak ridging aloft and drier
air. Cold air advection slows with 850 mb temperatures bottoming out
around -15c by Saturday morning. Scattered clouds dissipating,
overall mostly clear except some ocean-effect activity across the
Outer Cape, looking at lows dropping into the teens. Tack on the
winds, looking at wind chill values down into the single digits.

&&

Short term /Saturday through Saturday night/...

Saturday into Saturday night...

One more piece of mid-level energy through the prevailing cyclonic
flow across the region. Some low to mid level decks and perhaps
some flurry activity over the west portions of CT and Massachusetts. Otherwise
thereafter a ridge of high pressure builds into the region yielding
an increasing presence of surface high pressure. Northwest winds becoming
light and variable late Saturday into Saturday night as conditions
turn mostly clear. Highs barely getting above freezing, more than
likely feeling like the teens and 20s given the northwest breeze. Lows
back down into the teens, possibly single digits, considering the
light and variable flow, mostly clear conditions. Decent signs of
radiational cooling and thus leaning with the coldest MOS guidance.
Wicked cold.

&&

Long term /Sunday through Friday/...

*/ highlights...

* wintry precipitation likely Sunday evening into Monday
* another system may bring precip sometime Tuesday or Wednesday
* another round of unseasonably cold weather late in the week

*/ overview...

Models and ensemble members are in generally good agreement on much
of the long term, particularly with the synoptic pattern. After
starting the period with below normal temperatures, two systems
may bring precipitation to southern New England. The first one moves
through the region Sunday into Monday, bringing a period of mainly
snow to much of the area, changing to rain along the coastal plain.
The second one, a coastal system, may bring another round of snow/rain
to the region sometime Tuesday or Wednesday. Or it may stay far enough
to the south that there may not be much, if any, precipitation. An
Arctic front will bring below normal temperatures back to the region
late next week.

*/ Daily discussion...

Sunday and Monday...
much of the day Sunday should be fairly dry as weak upper ridging
moves over southern New England and high pressure moves slowly
offshore. Then a shortwave moves through the upper level flow over
the area early Monday. There is still some uncertainty with the
track of the associated low pressure system and the potential
development and location of a secondary low pressure system.
Expect the models to start coming into better agreement later
today as the energy responsible for the system moves onshore and
is better sampled.

The track of the primary low and any secondary low development will
affect thermal profiles. So this is leading to a bit of uncertainty
with the p-type through the event. At this time, believe it will
be a mainly snow or rain scenario, but there is a low probability
of a period of ice during the transition as the warmer air moves
in aloft. While it is still a bit too early to detail exact snow
amounts, confidence is high that a portion of the area could have
accumulations in the 3 to 6 inch range. Most of the area should
see at least a dusting of snow, with the possible exception being
the islands.

Monday night and Tuesday...
the 00z runs of the models/ensembles indicate high pressure will
build into the region and be the dominant feature during this
time. However, this is a change from previous runs which had a bit
more activity, especially during Tuesday. So this period remains a
bit uncertain and unsettled.

Wednesday and Thursday...
confidence remains rather low for this period. A broad upper
level trough in the Great Lakes moves eastward over southeastern
Canada and the northeastern U.S. A strong shortwave will rotate
through this trough bringing another period of unsettled weather
to southern New England. The low pressure system associated with
this shortwave looks to be a coastal low at this point, but there
is significant spread in the ensembles as to how close this system
comes to southern New England. Beyond the potential precipitation
event, another shot of Arctic air is expected to move into the
region.

&&

Aviation /19z 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/...high confidence.

18z update...

VFR. Northwest winds sustained around 10 to 15 kts, gusting up to 35 kts.
Scattered-broken low-end VFR cigs with the chance of a flurry and slight
restrictions in visibility especially over west Massachusetts and CT.

Snow and wind activity diminish overnight into Saturday. Winds
becoming light and vrb into Saturday night.

Kbos taf...W/NW flow. Gusts up to 35 kts.

Kbdl taf...W/NW flow. Gusts up to 30 kts.

Outlook /Sunday through Wednesday/...

Saturday night through Sunday...high confidence.
Mainly VFR conditions expected. Lowering clouds and approaching
precipitation may result in a trend towards MVFR after noon on
Sunday.

Sunday evening through Monday...moderate confidence.
MVFR/IFR develop in snow Sunday night. Snow may change to rain
across portions of the coastal plain Monday. Accumulating snow is
likely across the interior. Some improvement is possible late
Monday as precipitation comes to an end.

Tuesday...low confidence.
Improving conditions. Mainly VFR.

&&

Marine...

Forecaster confidence levels.

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

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

Northwest winds with gale force gusts continuing into the evening hours.
With the gradual increasing presence of high pressure, building
across the region tonight towards late Saturday into Saturday night,
should see northwest winds taper allowing wave activity to relax. Gale
warnings dropping off during the evening hours with follow-up small
craft advisories concluding through Saturday. Initial wave heights
5 to 8 feet diminishing.

Outlook /Sunday through Wednesday/...

Sunday...high confidence.
Good boating weather with winds and seas below Small Craft Advisory
thresholds.

Monday...moderate confidence.
Seas below 5 feet will slowly increase once again from the south
as low pressure approaches the waters. Winds increase as well and
small craft advisories will be necessary. There is a moderate
probability of north-northwest gales.

Tuesday...moderate confidence.
Northwest winds and seas slowly diminish. Small craft advisories will
likely continue through much of Tuesday. In addition, there is a
moderate probability of north-northwest gales during the morning.

&&

Box watches/warnings/advisories...

CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 10 am EST Saturday for anz231>234.
Small Craft Advisory until 4 am EST Saturday for anz230.
Small Craft Advisory until 1 am EST Saturday for anz236.
Small Craft Advisory until 7 am EST Saturday for anz235-237.
Gale Warning until 10 PM EST this evening for anz250-254.
Gale Warning until 8 PM EST this evening for anz251-255-256.

&&

$$

Synopsis...rlg/sipprell

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