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Area forecast discussion 
National Weather Service Taunton Massachusetts
739 am EDT Tuesday Jul 26 2016

Synopsis...
high pressure will bring dry but continued hot conditions today
and Wednesday. A cold front will slowly push into the region
during Thursday, then looks like will linger through this
weekend.

&&

Near term /until 6 PM this evening/...

730 am update...

Mainly clear skies across the region early this morning, except
for some wispy cirrus clouds in a few spots at 11z. Noting west-SW
winds in place across most of the region at 10 knots or less, with
calm winds in valley locations. Expect winds to shift to west-northwest
during the morning/midday hours as mid level short wave shifts east.

Temps already recovering to the 70s to around 80 at most
locations, which was close to previous forecast. Have updated near
term to bring conditions current.

Previous discussion...

High pressure builds in from the west bringing subsidence and
sunshine and deep mixing. But lingering moisture near 850 mb
should allow for some diurnal clouds to develop.

Mixing will bring down some wind gusts near 20 knots. Temps
aloft are roughly 15c-17c on the GFS and 16c-18c on the European model (ecmwf).
Mixing should allow for Max surface temps in the upper 80s to mid
90s. Dew points over upstate New York are in the mid 60s, with
low 60s to the north and west. This will mean a little less
humidity, but still enough to be noticed.

&&

Short term /6 PM this evening through 6 PM Wednesday/...
tonight... high pressure builds in with diminishing wind. Dew
points 60 to 65 will keep min temps in the 60s, with low 70s along
the coast.

Wednesday... high pressure remains in control with sunshine. Upper
flow shows a weak shortwave moving through, but less cloud-level
moisture for sky cover. Light wind near the surface will allow for
developing sea breezes along the coasts. Temps aloft around 18c
should support sfc Max temps in the interior in the low to mid
90s, cooler values near the coastline. Dew points linger around
60 or in the lower 60s.

&&

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

* cold front approaches the region during Thursday
* showers and isolated thunderstorms remain possible Friday into
the weekend

Overview and model preferences...

00z model suite remains in pretty good agreement through
Thursday, then continue to show wide model spread from Thursday
night Onward. This appears to be dependent upon development of
short waves in the nearly zonal 500 mb flow across the northeast,
which will start to back to SW as broad mid level troughing
develops across the Great Lakes into the weekend. The big
differences come into play as models handling the slow movement of
the front out of northern New England differently, along with any
low pressure waves that move along it.

One thing that is in somewhat good agreement is that the front
should push into the region around Friday, then will stall in the
west-SW mid level flow through most if not all weekend.

Used a blend of available guidance through Thursday, then went
with mainly ensemble approach beyond that.

Details...

Wednesday night...will remain dry and muggy conditions. Patchy late
night/early morning fog develops mainly along the coast and some of
the interior valleys, especially interior east mass. Overnight lows in
the lower-mid 60s well inland, ranging to around 70 along the coast
and urban centers.

Thursday...models begin their solution variance during this
timeframe, but in fair agreement. Will see another hot and humid
day, especially along the South Coast.

Timing of slow moving front remains in question, but does appear
scattered showers/isold thunderstorms may push into north central and
west mass into north central CT during the afternoon/evening hours ahead
of the front. Have carried low chance pops there, with isold
showers possible further S and east. Kept isold convection going, can
not rule out entirely with marginal instability in place. Decent
850 mb-500 mb lapse rates of 6-6.5c/km, with best shot during Max heating
of the day.

Expect highs in the lower-mid 90s away from the coast, warmest
across the CT valley, ranging to the upper 70s-mid 80s near the
coast possibly touching 90 in Boston and on the North Shore.

Thursday night and Friday...model solutions continue to Widen
during this timeframe with the movement, or lack thereof, of the
front out of S VT/NH. Also questions on development of low
pressure along this front, with the GFS being most robust. Have
kept chance pops going, as models do generally bring in scattered
showers, and kept isold thunder as well. With more clouds around,
will see high temps on Friday 5-10 degrees cooler than Thursday,
mainly in the 80s.

Saturday and Sunday...high uncertainty remains during this
portion of the forecast, with a continued low confidence forecast.
Both the European model (ecmwf) and Canadian ggem models move low pressure off the
mid Atlantic coast during Saturday, with precip working into the
region, while the GFS remains the outlier. More questions on
timing of short wave in the 500 mb flow on Sunday, so kept low chance
pops going there as well.

Monday...low confidence continues. Do have low chance pops going
inland into the afternoon, then have trended drier. Expect
temperatures to run close to seasonal normals.

&&

Aviation /12z Tuesday through Saturday/...
forecaster confidence levels.

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

Short term /through Wednesday/...high confidence.

Today...VFR. West-northwest winds with gusts 15-20 knots during the
afternoon.

Tonight...VFR. Patches of IFR cigs/vsbys in fog late at night.

Wednesday...VFR. Fog Burns off around sunrise. Light variable
wind becoming onshore along the coastline.

Kbos taf...high confidence in taf.

Kbdl taf...high confidence in taf.

Outlook /Wednesday night through Saturday/...

High confidence Wednesday night. Moderate confidence Thursday
through Saturday.

Wednesday night...mainly VFR conditions. Patchy fog possible
after 07z-08z through 12z along the immediate South Coast, Cape
Cod and the islands.

Thursday through Saturday...mainly VFR, except MVFR ceilings/visibilities
possible in scattered showers and thunderstorms. Potential for
local MVFR-IFR in patchy fog and low ceilings each night.

&&

Marine...
forecaster confidence levels.

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

Short term /through Wednesday/...high confidence.

Winds remain below 20 knots and seas below 5 feet through the
period. Winds become northwest today, then variable tonight and
Wednesday.

Outlook /Wednesday night through Saturday/...moderate to high
confidence.

Wednesday-Thursday...winds and seas below small craft criteria.
Patchy late night/early morning fog with reduced visibilities.
Isolated showers/thunderstorms possible late Thursday/Thursday
night.

Friday-Saturday...winds shift to S-southeast but remain below small
craft levels. Swells will build to around 5 ft on the southern
outer waters Friday night into Saturday, then should subside.
Patchy fog and scattered showers/thunderstorms will reduce
visibilities.

&&

Fire weather...
much drier conditions are expected today across southern New
England behind the departing cool front. Minimum relative humidity
is expected to range from 30 to 40 percent across much of the
area. The exception is along Cape Ann and the cape/islands, where
minimum relative humidity values of 40 to 60 percent are forecast. Northwest
winds around 10 mph may gust to 20 mph at times.

Winds are expected to be lighter on Wednesday with nearshore sea
breeze development. However, minimum relative humidity will again reach 30 to 40
percent across the interior. Along east coastal Massachusetts and southern
RI, sea breezes will allow for higher minimum relative humidity of 40 to 70
percent.

&&

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

&&

$$
Synopsis...wtb/evt
near term...wtb/evt
short term...wtb
long term...evt
aviation...wtb/evt
marine...wtb/evt
fire weather...wtb

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