Area Forecast Discussion
Issued by NWS Boston, MA

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FXUS61 KBOX 141758
AFDBOX

Area Forecast Discussion
National Weather Service Taunton MA
1258 PM EST Thu Dec 14 2017

.SYNOPSIS...
High pressure near Chicago builds eastward providing dry but
cold conditions this afternoon into Friday morning. Two areas of
low pressure, one tracking across the eastern Great Lakes and
the other well offshore may bring a period of light snow or
flurries late Friday into Friday evening. Temperatures will
turn milder early next week, but will also bring the chance of
rain and/or snow showers. Mainly dry conditions expected Tuesday
into Wednesday, but some light precipitation may linger across
portions of the region.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

1 PM Update...

Per latest satellite imagery back edge of the cloud shield
moving across Cape Cod and the Islands and will be offshore
shortly. Dry but cold this afternoon with good CAA to follow
given -18C at 850 mb upstream over NY state, streaming this way.
Also as ocean wave departs and intensifies will see WNW winds
begin to increase 4p-7p today. Thus developing gusty WNW winds
will add to the chilly conditions for the evening commute.


&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
Tonight...
Clear skies and diminishing wind as high pres moves to the mid
Atlc coast with ridging extending into New Eng. This will result
in good radiational cooling which will be enhanced by fresh
snow cover near the coast. Lows dropping into the single
numbers, except teens near the coast.

Friday...
Next mid level trough and shortwave approaches from the west as
coastal low pres develops well to the south. Sunshine will
give way to increasing clouds in the afternoon as the column
moistens. Modest large scale forcing develops late in the day
ahead of the mid level trough with best chance for any late day
snow showers across SE New Eng assocd with a weak inverted
trough and increased low level moisture. Still rather cold with
925 mb temps -8 to -10C which will yield another day with highs
mostly in the 20s, but winds will be lighter and less of a
factor.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
Overview...

Overall, noting an active, progressive pattern in place across
the lower 48, especially starting this weekend as the blocking
high amplitude ridge across the western U.S. breaks down. This
will bring weak mid level short waves eastward in the fast flow
aloft. After several days of below normal temperatures, models
continue to signal milder air starting to move into the
northeast early next week.

With any progressive pattern, however, noting widening model
solution spread with the timing and track of weather systems
especially across the northern stream, so have lower confidence
with the track and timing of any systems beyond Monday.

For now, will see a couple of weak lows passing near or SE of
New England into this weekend, each bringing some light rain
and/or snow showers but will move across rather quickly. As the
upper pattern becomes nearly zonal, will start to see
temperatures moderating closer to seasonal normals by early next
week, though may still see some light precip into mid week
mainly along coastal areas and across the E slopes of the
Berkshires.

Details...

Friday night and Saturday...

Light precipitation along the western periphery of low pressure
moving well SE of the 40N/70W benchmark brings scattered snow
showers Friday night. At this point, the best chance will occur
along the immediate S coast, Cape Cod and the islands. Current
timing suggests that the precip should push offshore by Sat
morning. With light QPF amounts, less than 0.1 inches, should
see less than an inch snow accumulations.

As the low exits, W-NW winds will pick up as low level lapse
rates increase during Saturday. Could see gusts up to 25-35 kt,
highest across SE areas where the highest low level jet moves
across. With temps running up to 10 degrees below seasonal
normals, will see wind chill values in the teens to lower 20s
during the day.

Sunday and Monday...

High pres ridge builds east across the eastern seaboard by
Sunday morning, so winds will diminish by daybreak. Will see
another cold day, however, as mid level winds continue from the
NW, though will start to back to W later in the day. Another
chilly day with highs from the mid-upper 20s across the higher
inland terrain to the 30s across the coastal plain.

A weak warm front will approach Sunday night, so may see some
overrunning precip try to develop across western by around 00Z
Monday, then pushing E quickly through the night and during
Monday. Temps will hold mainly in the 20s except the lower-mid
30s along the immediate coast overnight as the precip develops.
Thermal profiles suggest mainly light snow Sun night, but not a
lot of precip to work with so not expect much in the way of snow
accumulations at this point.

As winds shift to SW, will see milder air finally push into the
region. Expect spotty snow showers to change to rain during the
morning, but may linger a bit longer across the higher inland
terrain. Expect highs close to seasonal normals for mid
December.

Tuesday and Wednesday...

With a nearly zonal mid level steering flow across most of the
country, will see weak systems work eastward but tend to weaken
as they approach. Not expect much in the way of precipitation
either Tuesday or Wednesday, but timing and track of systems are
in question with the fast flow aloft. Have mentioned only
slight chance POPs across the higher inland terrain and near the
coast through this timeframe, but confidence is low.

&&

.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...

Thru 00z...high confidence.

VFR and dry with developing WNW wind increasing to 15-20 kt,
possibly up to 25 kt Cape Cod and islands.

After 00z...high confidence.

VFR and dry with gusty WNW winds 15-20 kt diminishing after
midnight.

Friday...some uncertainty how far north snow and MVFR conditions
track

VFR but trending toward MVFR south coast and islands including
Cape Cod late in the day with light snow possible. Elsewhere VFR
prevails. Light winds.

Friday night...some uncertainty on northward extent of MVFR and
snow during the evening.

MVFR in light snow possible south coastal MA including Cape Cod
and Islands. Elsewhere VFR. Light winds becoming WNW.

KBOS Terminal...High confidence in TAF.

KBDL Terminal...High confidence in TAF.

Outlook /Saturday through Monday/...

Saturday through Saturday Night: VFR. Windy with local gusts to
30 kt.

Sunday: VFR.

Sunday Night: Mainly VFR, with areas MVFR possible. Chance
SHSN.

Monday: Mainly VFR, with areas MVFR possible. Slight chance
SHRA, slight chance SHSN.

&&

.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.

Today...
Diminishing winds through the morning, then W-NW winds will
increase this afternoon with gusts to 25-30 kt. Area of snow
this morning will reduce vsbys, mainly over south coastal
waters. SCA all waters.

Tonight...
Lingering SCA wind gusts in the evening then diminishing winds
overnight as high pres builds in from the west.

Friday...
NW winds shift to the SW in the afternoon. Speeds below 20 kt
with seas below SCA.

Outlook /Friday Night through Monday/...

Friday Night: Low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of seas approaching 5 ft. Chance of
snow showers.

Saturday through Saturday Night: Moderate risk for Small Craft
Advisory winds with gusts up to 30 kt. Local rough seas.

Sunday: Winds less than 25 kt. Seas locally approaching 5 ft.

Sunday Night: Winds less than 25 kt. Slight chance of rain
showers, slight chance of snow showers.

Monday: Winds less than 25 kt. Slight chance of rain showers.

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 1 AM EST Friday for ANZ230-232>234.
     Small Craft Advisory until 4 AM EST Friday for ANZ231-251.
     Small Craft Advisory until 4 AM EST Friday for ANZ235-237.
     Small Craft Advisory until 7 AM EST Friday for ANZ250-254>256.

&&

$$
SYNOPSIS...KJC/EVT
NEAR TERM...Nocera
SHORT TERM...KJC
LONG TERM...EVT
AVIATION...Nocera/EVT
MARINE...KJC/EVT



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