Area Forecast Discussion
Issued by NWS Boston, MA

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000
FXUS61 KBOX 091728
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1228 PM EST Fri Dec 9 2016

.SYNOPSIS...

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 /UNTIL 6 PM THIS EVENING/...

1230 pm update...No major changes to the forecast which is on
track.

Cyclonic flow persisting through which NW winds blow. Can see just
how well mixed the environment is with the 12z soundings allowing
the mix-down of drier air and faster winds. Seeing gusts on up to
35 mph and combined with forecast highs into the 30s, with the high
terrain into the upper 20s, it is going to feel much colder with
wind chill values 10 degrees cooler making it feel closer to the
teens.

Cold air advection proceeding aloft, H85 temperatures right now
around -10C falling to -15C through the day. Just look at the
difference between the 12z Chatham sounding and that of Albany.
That`s some cold Arctic air associated with a reinforcing cold
front presently sweeping the region. Scattered cloud decks, more
broken to the W and out across the Outer Cape (per ocean effect).
Likely to see some flurry activity off the Great Lakes extend over
the mountains into the CT River Valley. Have prevailed accordingly.

Good day for hot chocolate. Question is how many marshmallows?

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM SATURDAY/...

Our region should remain in between the major weather features
tonight and Saturday. Mid level flow is fairly zonal, with a
stronger shortwave arriving Saturday. At the surface, high
pressure remains to our southwest, with a low pressure over the
Maritimes.

Expecting gusty northwest winds to continue, although not quite
as strong as today. Not much chance for precipitation, due to
lacking humidity. However, there should be enough moisture for
some clouds as the shortwave arrives.

Temperatures will be 10-15 degrees below normal.

&&

.LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/...

*/ 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 /18Z 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. NW winds sustained around 10 to 15 kts, gusting up to 35 kts.
SCT-BKN low-end VFR cigs with the chance of a flurry and slight
restrictions in visibility especially over W MA and CT.

Snow and winds 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 /Saturday Night through Tuesday/...

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/...High confidence.

1230 pm update...No major changes to the forecast which is on
track.

Winds and seas on track. NW sustained around 10 to 15 kts with
gusts up to 35 kts outside the inner harbors and sounds. Waves
building 5 to 8 feet. Will see winds diminish as we go into
Saturday allowing wave activity to diminish. Otherwise Gale
Warnings continue much of today.

Outlook /Saturday Night through Tuesday/...

Saturday night and Sunday...High confidence.
Winds and seas continue to diminish.

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 N-NW gales.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...

CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 7 AM EST Saturday for ANZ231>234.
     Small Craft Advisory until 4 AM EST Saturday for ANZ230-236.
     Small Craft Advisory until 6 PM EST Saturday for ANZ235-237.
     Gale Warning until 10 PM EST this evening for ANZ250-254.
     Gale Warning until 6 PM EST this evening for ANZ251-255-256.

&&

$$

SYNOPSIS...Belk/RLG
NEAR TERM...Belk/RLG/Sipprell
SHORT TERM...Belk
LONG TERM...RLG
AVIATION...Belk/RLG/Sipprell
MARINE...Belk/RLG/Sipprell


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