Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
954 PM EDT sun Aug 28 2016

Synopsis...
a cold front enters southern New England tonight and then exits
Monday afternoon, which may be accompanied by a spot shower or
thunderstorm. Weak high pressure brings dry weather Tuesday. Warm
and humid weather returns Wednesday ahead of another cold front,
which will bring the chance for showers and thunderstorms
Wednesday afternoon into Thursday morning. Large Canadian high
pressure will bring dry, Fall-like weather late this week into
the weekend, with mild days and cool nights.

&&

Near term /until 6 am Monday morning/...

Changed timing of rainfall chances this evening. Starting to lose
confidence in any thunderstorms across southern New England
overnight. Latest mesoanalysis showed very little instability to
work with. Radar trends have also indicated any convection
weakening/dissipating as it approaches western New England.
Believe this to be the result of stronger convection over central
and western PA dominating the southerly inflow. Despite that,
still left a mention of isolated thunderstorms after midnight,
generally along and north of Route 2, for now. Will continue to
evaluate, and make changes as needed.

Besides that change, brought the next several hours back in line
with observed trends.

Previous discussion...

Gorgeous late Summer weather this evening with warm
temps...comfortable humidity and light winds with high pressure
anchored from the Maritimes thru the northeast. Short wave trough
and attending cold front approach the region later tonight.

As of 715 PM, the hrrr had the best handle on thunderstorms across
central New York state. The mid level trough deamplifies with time and
west-southwest winds ahead of the front limit convergence. Thus
overall weak synoptic lift. However sufficient moisture and
marginal instability will allow for a slight chance for a shower
or isolated thunderstorm mainly north of the Route 2 corridor in
northern Massachusetts into northeast Massachusetts later tonight. However most of the
region remains dry overnight. No changes to current forecast of
precipitation probabilities.

It will be a mild night given the prefrontal environment/warm
sector. Increasing humid as dew pts climb into the low and mid 60s
especially across CT/Rhode Island and southeast Massachusetts. This may result in some
patchy fog toward morning. Made minor downward adjustments to
temperature on Cape Cod and the islands, since Nantucket was
reporting only 67 degrees.

&&

Short term /6 am Monday morning through Monday night/...
Monday ...

Low risk of an isolated shower/T-storm in the morning with
greatest risk over eastern Massachusetts. Most places remain dry as cloud
cover limits instability and west-southwest winds yield weak
convergence. Mid level dry air and associated subsidence rush in
from the northwest to southeast yielding dry and partly sunny
conditions by afternoon...mid afternoon South Coast and islands.

Warm with highs in the mid to upper 80s...perhaps briefly touching
90 in a few spots. However west-northwest winds 10-20 mph behind
the front will yield lower humidity during the afternoon. Hence a
very nice afternoon shaping up.

Monday night ...

Post frontal airmass overspreads the region resulting in dry
weather...less humid and cooler conditions along with light winds
and mostly clear skies. Leaned toward the cooler MOS given
decoupling of the blyr is likely.

&&

Long term /Tuesday through Sunday/...
highlights...

* cold front brings the chance for showers/thunderstorms Wednesday
afternoon into Thursday morning.
* Dry, fall-like conditions move in for Friday and Saturday with
mild days and cool nights

Tuesday...weak high pressure ridge builds across southern New
England, then off the coast. Skies will be sunny with highs in the
lower 80s away from the coast. Humidities will be on the low side
with dewpoints in the mid and upper 50s. With a light pressure
gradient across the region, sea breezes will bring slightly cooler
temperatures along the shoreline.

Wednesday and Wednesday night...

Another cold front begins to approach north and west mass Wed. Afternoon.
However...it now appears that there will be a little more ridging
over southern New England...induced by a weak tropical system off
the mid-Atlantic coast...that remains well to our south. This may
delay the frontal passage until Wed night...then off the coast
Thursday morning. Will see warm and more humid conditions ahead of
this front as SW winds pick up. Noting the pwats do increase by
Wednesday evening to around 1.6 inches, so could see some brief
heavy downpours with any showers or thunderstorms across central
and southern areas toward evening and overnight. Have gone with 40
to 50 percent probabilities. Highs Wed in the mid 80s. Lows Wed
night in the 60s.

Thursday...the European model (ecmwf) model slows the front down the most and since
this has been consistent, have continued the chance of showers in
southeastern sections through the morning and early afternoon.
Will still see mild temperatures as the cooler air does not work
into the region until later in the day. Dewpoints drop to the
upper 40s and lower 50s Thursday night. Expecting lows Thursday
night in the 50s except 60-65 cape and islands.

Friday through Sunday...large sprawling high pressure will move
from the Great Lakes Fri to New England Sat...then off the coast
Sunday. It will bring cool temps especially Friday and Saturday
mornings, with lows reaching the upper 40s in northwest Massachusetts and
lower 50s elsewhere. Highs both Fri and Sat should hold in the
70s. As the high moves off the coast, will see a slight warmup on
Sunday with highs reaching the lower 80s.

&&

Aviation /02z Monday through Friday/...
forecaster confidence levels.

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

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

VFR, but isolated shower or thunderstorm with highest probs
across northwest MA, then shifting into northeastern Massachusetts toward
sunrise. High forecast confidence.

Monday...VFR with low risk of a spot shower or T-storm eastern Massachusetts
in the morning then shifting to South Coast midday, then offshore
by mid afternoon. West-southwest winds in the morning becoming northwest
10-20 kt by midday. High confidence.

Mon night...light north-northwest winds becoming variable late. VFR and dry
weather too.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Tuesday through Friday/...

Tuesday...high confidence. VFR. Light west-SW winds Inland. Sea
breezes along both coasts likely. Patchy fog late Tue night with
local MVFR-IFR visibilities.

Wednesday...moderate confidence. Mainly VFR. May see local MVFR
conditions in scattered rain showers/thunderstorms and rain across north central and west mass
during the afternoon.

Wednesday night-Thursday...moderate confidence. Mainly VFR. Local
MVFR-IFR ceilings/visibilities in scattered rain showers/thunderstorms and rain as cold front crosses
the region Wed night/early Thu. Scattered showers may linger
until around midday Thursday before improving.

Friday...high confidence. VFR.

&&

Marine...
forecaster confidence levels.

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

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

715 PM update ...

Tonight...

Fairly light winds with ridge of high pres over the waters.
However southeast swells from Hurricane Gaston beginning to enter
the waters southeast of Nantucket as of 3 PM. Dry weather and good
vsby with just a small chance of an isolated shower/T-storm well
after midnight.

Monday ...

Light west-southwest winds in the morning become west-northwest
during the afternoon with gusts up to 20 kt near shore possible.
Isolated shower/T-storm possible until early afternoon then
offshore. Southeast swells of 3-6 ft across the ocean waters.

Monday night ...

North-northwest wind with high pres building in from the west. Dry weather and
good vsby. Southeast swells of 3-6 ft from Gaston persist.

Outlook /Tuesday through Friday/...

Tuesday...high confidence. Light north-NE winds shift to southeast during
the day. May see briefly reduced visibilities late Tue night in
patchy fog on the nearshore waters. S-southeast swells from Hurricane
Gaston continue on the outer waters. Small craft advisories may
need to be continued for some 5 ft seas...will evaluate in
subsequent forecasts.

Wednesday...moderate to high confidence. SW winds increase, with
gusts up to 20 kt mainly across the eastern waters where seas will
increase to around 5 ft. Local visibility restrictions in
scattered showers/thunderstorms may approach the eastern waters
Wednesday afternoon.

Wednesday night-Thursday...moderate confidence. A cold front
crosses the waters with scattered showers/thunderstorms Wednesday
night into early Thursday morning. A few showers may linger
through midday across the southern waters. Winds shift from SW to
west-northwest by Thursday morning, then north-NE on the eastern waters Thursday
afternoon. Seas will be diminishing to 3 to 4 ft.

Friday...high confidence. North or north-northwest winds at 15 to
20 kt with seas between 3 and 5 ft. A marginal Small Craft
Advisory is not out of the question, especially for the outer
waters.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory from 2 am Monday to 8 am EDT Tuesday for
anz250.
Small Craft Advisory from 6 am Monday to 8 am EDT Tuesday for
anz254.
Small Craft Advisory from noon Monday to 8 am EDT Tuesday for
anz255-256.

&&

$$
Synopsis...nocera/gaf
near term...Belk/nocera/gaf
short term...nocera
long term...gaf
aviation...Belk/nocera/gaf
marine...nocera/gaf

National Weather Service Glossary of Abbreviations