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Area forecast discussion
National Weather Service Taunton Massachusetts
1223 PM EST Thu Dec 8 2016

Synopsis...

A strong front crosses the region late today. Mainly dry, but
unseasonably cold temperatures are on tap for our region Friday
into Saturday. Low pressure will likely bring some rain/snow
Sunday into Monday. A shot of Arctic air is then expected by mid
to late next week.

&&

Near term /until 6 PM this evening/...

1230 PM update...no major changes to the forecast.

Definitely hazy on the drive into work this morning. No surprise
given the light winds and shallow inversion discerned from the 12z
sounding this morning. Many locations dropping down at or below 1
to 2 miles in visibility, some places still low given how light
the winds continue to be and the trapped cold air within the
sheltered valleys. Expect that this fog should lift as we go
through the day as temperatures warm.

Back to the 12z soundings, fair amount of dry air within the low
levels. Seeing returns from WSR-88D emerging out of a mid-level
deck around 5-7 kft agl attendant to some weak forcing out ahead
of a stretch mid-level shortwave through the overall cyclonic flow.
Accompanying cold frontal boundary with limited moisture given a
Continental-origin airmass associated, likely not going to see
much in any way of sprinkle / flurry activity except across the
high terrain. Much of the activity falling in the form of virga.

Mostly cloudy most of today with some cloud break late. A westerly
flow, looking at seasonable temperatures with highs getting up
around the low 40s. It'll be late when westerly flow turns towards
northwest associated with a reinforcing Arctic front and colder air. So
one last day of normal conditions and then we'll begin the downward
temperature trend going into this weekend.

&&

Short term /6 PM this evening through 6 PM Friday/...

Tonight...

Arctic cold front moves offshore during the night. Lowering
humidity, meaning even less risk for precipitation. West winds
will increase slightly, in response to the increased pressure
gradient. There should be enough of a surface inversion to prevent
the maximum momentum Transfer. Below normal temperatures.

Friday...

Colder air will continue to overspread southern New England. More
sunshine early in the day will lead to deeper mixing, and stronger
west to northwest winds. Diurnal clouds expected to develop
through the day. Temperatures should only rise at most 10 degrees
from morning lows. Mainly dry weather should continue. There is
the possibility for a stray snow shower across the interior, but
not a large one.

&&

Long term /Friday night through Wednesday/...

*/ highlights...

* unseasonably cold but mainly dry Saturday
* wintry precipitation possible Sunday into Monday
* another system may bring precip Tuesday into Wednesday

*/ 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
snow to much of the area, changing to rain along the coastal
plain. The second one may bring another round of snow/rain to the
region Tuesday into Wednesday. Or it may stay far enough to the
north that there will be little, if any, precipitation. Then an
Arctic front will bring below normal temperatures to the region
once again.

*/ Daily discussion...

Friday night through Saturday...
northwesterly flow keeps below normal temperatures in the region
through this period. High temperatures Saturday will have trouble
getting above freezing. Most areas will be below freezing for most
of this time. The South Coast may see high temperatures just above
freezing. Low temperatures should fall into the teens Friday and
Saturday nights. Otherwise, high pressure will keep dry weather in
the area.

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 offshore.
Then a shortwave will move through the upper level flow over the
area late Sunday into early Monday. Low pressure moves eastward
just south of southern New England during this time, keeping cold
air in the region. Thermal profiles continue to indicate a snow or
rain scenario with all snow across the interior and a period of
snow followed by a change to rain across the coastal plain.
Ensemble quantitative precipitation forecast amounts indicate a rather minor snow event, with the
highest confidence in 1-3 inch snow totals, and a low probability
of up to 6 inches in the highest terrain. Confidence is relatively
high for a precipitation event to occur, however, confidence is
low in the details.

Tuesday and Wednesday...
confidence remains rather low for this period, especially with
changes seen since last night's model runs. The 00z GFS and its
ensembles indicate a low pressure system moving through Quebec
will bring an Arctic cold front through southern New England. If
this solution is correct, it will result in another precipitation
event. The 00z European model (ecmwf) on the other hand indicates brings a shortwave
over the area resulting in some light precip, but keeps the low
pressure system well north of the area. Again, confidence is quite
low. Expect below normal temperatures to come in Wednesday.

&&

Aviation /18z Thursday through Tuesday/...

Forecaster confidence levels...

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

Short term /through Friday/...high confidence.

18z update...

Rest of today...
lingering MVFR vsbys the next hour or two in the CT River Valley
with pockets of MVFR cigs scattered-broken over the southeast New England terminals.
All of this should clear out towards late as winds increase out of
the west with gusts around 15-20 kts. Such winds just beginning to
emerge across west and central upstate New York / PA.

Tonight...
blustery west/northwest winds continuing along the immediate coast and high
terrain with gusts up to 25 kts, otherwise VFR with overall light
winds.

Friday...
mainly VFR. Low risk for brief MVFR cigs toward the Berkshires. Northwest
winds increasing across the interior with gusts up to 35 kts possible
into afternoon.

Kbos taf...west flow increasing towards late and continuing overnight
around 270-280 with gusts up to 25 kts.

Kbdl taf...morning fog/haze should lift towards noon, 15-16z, and
thereafter VFR. Increasing west winds towards late dropping off over-
night.

Outlook /Friday night through Monday/...

Friday night through Saturday...high confidence.
Mainly VFR conditions expected. A period of lower clouds Friday
night may result in some MVFR conditions.

Sunday and Monday...moderate confidence.
VFR conditions to start. Conditions may lower to MVFR/IFR later
Sunday afternoon and Sunday night in rain and/or snow. Some
improvement is possible late Monday as precipitation comes to an
end.

&&



Marine...
forecaster confidence levels.

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

Short term /through Friday/...high confidence.

1230 PM update...no major changes to the forecast.

Today and tonight...
with cold frontal passage late today, expect an increase in west-northwest
winds late in the day and continuing into tonight. Gusts up to
25-30 kt likely at times. Conditions may briefly diminish below
Small Craft Advisory levels across the outer Rhode Island coastal waters
today. That said, will continue the advisory through today, with
the expectation of increasing winds and seas later this afternoon.
Small craft advisories will start across most of the other coastal
waters this afternoon.

Friday...
strong cold advection will result in widespread northwest wind gusts of
25 to 35 knots. Not enough confidence 35 kt will be widespread
enough, long enough, to convert the gale watches over the eastern
outer Massachusetts coastal waters to gale warnings. Will let the next shift
take another look.

Outlook /Friday night through Monday/...

Friday night...high confidence.
Small craft advisories are likely with winds gusting over 25
knots and seas on the outer waters 5 to 6 feet. There is a
moderate probability of northwest gales.

Saturday and Sunday...moderate confidence.
Winds and seas slowly diminish, but generally remain above Small Craft Advisory
criteria until late Saturday night.

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,
with small craft advisories likely. There is a moderate probability
of north gales.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 7 PM this evening to 1 am EST
Saturday for anz231>234.
Small Craft Advisory from 7 PM this evening to midnight EST
Friday night for anz230-236.
Small Craft Advisory until 1 am EST Saturday for anz235-237.
Gale watch from Friday morning through late Friday night for
anz250-251-254.
Small Craft Advisory until 9 am EST Friday for anz250-254.
Small Craft Advisory from 7 PM this evening to 9 am EST Friday
for anz251.
Small Craft Advisory until 1 am EST Saturday for anz255.
Small Craft Advisory until 1 am EST Saturday for anz256.

&&

$$
Synopsis...Belk/rlg

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