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Area forecast discussion
National Weather Service Taunton Massachusetts
1015 am EST Thu Dec 14 2017

Synopsis...
fast moving departing low pressure south of New England this
morning gives way to a dry but cold afternoon. Cold conditions
will continue through the upcoming weekend. Scattered snow
showers may fall across south coastal areas and the higher
terrain Friday night into Saturday, along with gusty winds.
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/...

1010 am update...

Back edge of the snow shield at 10 am was moving across Cape Cod
and Nantucket, rapidly eastward and should be offshore by 11 am
or so. Latest snowfall reports indicate 1-3" from Hartford to
Providence into southeast Massachusetts including Cape Cod and the islands.

Satellite imagery indicates back edge of the cloud shield is
across central portions of CT/Massachusetts and moving steadily eastward.
So still expecting sunshine to develop from west to east late
this morning and afternoon. Previous forecast captures this well
so no major changes with this update.

Previous discussion...

Snow will exit the cape/islands by midday with gradual clearing
and increasing sunshine moving in from northwest to southeast during the
afternoon. Another unseasonably cold day with highs mostly 25-30
degrees with some lower 30s near the South Coast. Becoming
blustery in the afternoon with west-northwest gusts 20-30 mph developing
making it feel much colder.

&&

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 southeast 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 southeast 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 east slopes of the
Berkshires.

Details...

Friday night and Saturday...

Light precipitation along the western periphery of low pressure
moving well southeast 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 quantitative precipitation forecast amounts, less than 0.1 inches, should
see less than an inch snow accumulations.

As the low exits, west-northwest winds will pick up as low level lapse
rates increase during Saturday. Could see gusts up to 25-35 kt,
highest across southeast 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 west 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 east 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 /15z Thursday through Monday/...
forecaster confidence levels...
low - less than 30 percent.
Moderate - 30 to 60 percent.
High - greater than 60 percent.

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

15z update...

Back edge of the snow shield at 15z was moving across Cape Cod
and Nantucket, rapidly eastward and should be offshore by 16z or
so. Latest snowfall reports indicate 1-3" from hfd-pvd-pym
southward including Cape Cod and the islands. Satellite imagery
indicates back edge of the cloud shield is across central
portions of CT/Massachusetts and moving steadily eastward. Thus upward
trend to VFR all terminals late this morning into the afternoon.
Light winds become west-northwest and increase 15-20 kt 21z-03z. Previous
discussion below.

=================================================================

Today...high confidence.
Period of snow with MVFR-IFR conditions moves along the South
Coast and cape/islands through 16z. Northern edge of MVFR from
bdl-pvd with areas of IFR to the south, especially across the
cape/islands. Mainly VFR cigs along and north of baf-orh-owd.
Improving conditions this afternoon with gradual clearing from
northwest to southeast. West-northwest gusts 20-25 kt develop in the afternoon,
strongest higher terrain.

Tonight...high confidence.
VFR. Clear skies and light winds.

Friday...high confidence.
VFR with mid level clouds moving in during the afternoon. Areas
of MVFR cigs developing late afternoon cape/islands.

Kbos terminal...high confidence in taf. A few flurries possible
this morning but any vsby restrictions should remain to the
south.

Kbdl terminal...moderate confidence in taf. Brief MVFR
cigs/vsbys in light snow possible for a few hours this morning,
but lower conditions should remain to the south.

Outlook /Friday night through Monday/...

Friday night: mainly VFR, with local MVFR possible. Breezy.
Slight chance shsn.

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 west-northwest winds will
increase this afternoon with gusts to 25-30 kt. Area of snow
this morning will reduce vsbys, mainly over south coastal
waters. Small Craft Advisory all waters.

Tonight...
lingering Small Craft Advisory wind gusts in the evening then diminishing winds
overnight as high pres builds in from the west.

Friday...
northwest winds shift to the SW in the afternoon. Speeds below 20 kt
with seas below Small Craft Advisory.

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.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 3 PM this afternoon to 1 am EST
Friday for anz230-232>234.
Small Craft Advisory until 4 am EST Friday for anz231-251.
Small Craft Advisory from 3 PM this afternoon to 4 am EST
Friday for anz235-237.
Small Craft Advisory until 7 am EST Friday for anz250-254>256.

&&

$$
Synopsis...kjc/evt

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