Scientific Forecaster Discussion

Return to Local Conditions & Forecast

Without Abbreviations
With Abbreviations

Area forecast discussion 
National Weather Service Taunton Massachusetts
134 am EDT sun Jul 31 2016

Synopsis...
a series of weak low pressure centers will travel along a warm
front located over southern New England, bringing a few showers
or a thunderstorm today through Monday. High pressure will build
out of northern New England Tuesday through Friday, bringing dry
conditions. Temperatures will warm up toward the end of next week.

&&

Near term /until 6 am this morning/...
135 am update...

Tough to find warm front due to weak gradient but appears to
extend from northern CT into central and NE Massachusetts early this
morning. Regional radar mosaic shows most of the showers/storms
concentrated across central and eastern NY, where better moisture
convergence and lift associated with weak surface low exists.
Showers are more scattered in nature across southern New England
where lift is weaker but we have plenty of low level moisture.
This should remain case through daybreak as high-res and global
models keep better moisture convergence and lift from
frontogenesis to our west and north.

Warm/muggy night lows in 60s to around 70 and patchy fog, which
will be dense in spots near South Coast.

&&

Short term /6 am this morning through 6 PM Monday/...
during Sunday the warm front is expected to remain draped just south
of our area, as the weak low pressure gradually moves eastward. Thus
a continued modest overrunning setup is anticipated. For Sunday
have the highest (likely) pops in the western Massachusetts/north central CT
where the models suggest better forcing. Chance pops to the east.
With k indices in the lower 30s, cannot rule out isolated thunder
during Sunday. Skies are expected to be mainly cloudy through the
day. The combination of clouds and generally onshore flow is
expected to keep temperatures in the mid to upper 70s on Sunday.

During Sunday night models show the weak low pressure passing south
of New England. This will bring continued cloudiness to the area,
along with scattered showers/isolated T-storms. Lows mainly in the
60s are expected. With abundant low level moisture expecting some
areas of fog.

&&

Long term /Monday night through Saturday/...
highlights...

* unsettled weather through early Tuesday with scattered showers,
mainly over northern and western areas
* isolated thunderstorms possible across central and western
areas Monday afternoon/evening
* mostly dry weather expected Tuesday afternoon through Friday,
with a warming trend toward the end of next week

Overview and model preferences...

30/12z guidance continues to shower decent overall agreement with
synoptic trends over this portion of the forecast. Agreement on
some of the more significant details, not so much.

Latest guidance continues to show an open wave of energy in the
mid levels passing the northeast USA early next week. Then the mid
level flow transitions to a nearly zonal flow for the second half
of next week. One question which still needs to be answered is how
close does another mid level open wave get to southern New England
toward next weekend. This nearly zonal flow should lead to much
quieter weather during the middle of next week.

At the surface, there is some disagreement at how close a pair of
low pressures get to our region early next week. This will be key
to determining how quickly the risk for showers winds down
Tuesday. The majority of the guidance keeps these low pressures to
our south Monday into Tuesday. So while not expecting a washout,
have low confidence with this portion of the forecast, especially
with timing.

Used a blend of available model and ensemble guidance for this
portion of the forecast.

Details...

Monday through early Tuesday...

Expect a couple of low pressures to slowly ride along a stalled
front just off the southern New England coast into early Tuesday.
This will keep a good low to mid level moisture feed across the
region thanks to an east-southeast wind flow that will slowly back to NE
late Monday night into Tuesday as the final low pressure pushes
offshore.

The greatest risk for showers still appears to be Monday,
gradually diminishing Monday night into Tuesday. Greatest risk
for showers should be across the interior, but really anywhere in
southern New England has a shot at some showers or thunderstorms.

Will see the final low push offshore early Tuesday as it becomes
better organized. The last of the showers should start to
dissipate during the morning.

With the mainly onshore flow, expecting temperatures to run
several degrees below seasonal normals, especially toward the
coasts.

Tuesday afternoon through Friday...

This still looks like a mainly dry period of the forecast. Cannot
rule out a stray, isolated shower. There may be just enough
instability and moisture to generate one or two, especially across
the higher terrain of interior southern New England.

Temperatures should return to seasonal levels Wednesday, then
will warm further as winds become more S-SW as the high crests
across the region, then slowly pushes offshore. Humidity levels
will also slowly increase.

Saturday...a cold front is currently expected to cross our region.
This should lead to a chance of showers. Still lots of time to
work out the timing details.

&&

Aviation /05z Sunday through Thursday/...
forecaster confidence levels.

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

Low confidence through Monday.

Wide variety of conditions with VFR ceilings across much of region
but patches of IFR ceilings, especially where it rained last night
in western New England. Also IFR/LIFR in low clouds/fog around
South Coast, Cape Cod, and islands. Expect this to be case through
daybreak. During morning, we should see MVFR ceilings across most
of southern New England.

Despite light east/NE flow developing this afternoon, should be
enough drying at low levels to raise ceilings back to VFR.
Exception is around Cape Cod and islands, but even these locations
should improve this evening. VFR ceilings expected Mon.

Timing of showers is difficult, as scattered showers will be
around region today through Mon. Most of them should be
concentrated near Berkshires and Litchfield Hills this morning.

Kbos taf...low confidence. Spotty showers through morning.
Possibility ceilings stay VFR and do not lower to MVFR as
forecast today.

Kbdl taf...low confidence. Spotty showers through early afternoon.
Possibility ceilings lower to IFR for a few hours early this
morning.

Outlook /Monday night through Thursday/...

Monday night...moderate confidence. Mainly VFR. Scattered showers
possible at any time. Cannot rule out a heavier shower or
thunderstorm with local MVFR-IFR conditions, mainly from central
mass into north Connecticut Monday evening. Areas of late night/early
morning fog with IFR ceilings/visibilities Monday night.

Tuesday...high confidence in trends. Moderate confidence in
timing. Mainly VFR. Scattered showers across the CT valley through
north central and northeast Massachusetts Tuesday morning, then improving.
May see brief local MVFR conditions in any showers. Patchy late
night/early morning fog with MVFR-IFR conditions Tuesday night in
the normally prone areas.

Wednesday and Thursday...high confidence.
VFR. Just a few areas of MVFR possible in patchy late night/early
morning valley fog and in the usual fog prone locations.

&&

Marine...
forecaster confidence levels.

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

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

Winds and seas are expected to remain below Small Craft Advisory
thresholds through Sunday night. Areas of visibilities 1 to 3 nm in
areas of fog are possible at times tonight along the waters around
Nantucket, and isolated to scattered showers are possible over the
waters later tonight and Sunday. For Sunday night, visibility
restrictions possible in scattered showers and fog
patches.

Outlook /Monday night through Thursday/...high confidence.

Monday through Tuesday...relatively light winds and seas.
Visibility restrictions in patchy late night/early morning fog
both nights, and in scattered showers Monday and Monday night,
slowly improving on Tuesday. Isolated thunderstorms possible off
the Rhode Island coast Monday into Monday evening.

Tuesday night through Wednesday...persistent onshore winds
continue. A passing low pressure may generate rough seas across
the eastern coastal waters. Local visibility restrictions continue
Tuesday night in patchy fog, mainly after midnight through mid
morning Wednesday.

Thursday...tranquil boating conditions with light winds and seas
expected.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...none.

&&

$$
Synopsis...Belk/nmb
near term...jwd
short term...nmb
long term...Belk
aviation...jwd
marine...Belk/nmb

National Weather Service Glossary of Abbreviations