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Area forecast discussion 
National Weather Service Taunton Massachusetts
955 PM EDT Tuesday Sep 16 2014

Synopsis...
high pressure will build into the region bringing cooler and drier
weather through the remainder of the week. Some frost is possible
early Friday morning in some areas. The high will then slip
offshore and southwest flow behind it will allow temperatures to
warm to near or above normal Sunday and Monday. A cold front moves
through on Monday...followed by cooler weather by Tuesday.

&&

Near term /until 6 am Wednesday morning/...
10 PM update...the forecast is on track this evening as high
pressure builds into the region. Made a few minor updates to the
temperatures and sky grids to better track the current trends.

The clearing trend should continue through the early morning
hours. Northwest winds will bring in drier air. Dew points
upstream in upstate New York are in the 40s with a couple of high
30s. The pressure gradient over New England will be light
overnight. This will be favorable for radiational cooling...which
will allow temperatures to fall into the 40s away from the coast
and possibly a few spots in western mass/southwest New Hampshire that reach
the upper 30s.

Moist ground from daytime showers and temperatures falling to near the
dew point will increase the potential for patchy dense
fog...especially in the CT valley and associated valleys.

&&

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

High pressure in control. Light and variable winds continue. Mostly
sunny conditions. Sea-breezes along the shores. Cooler airmass aloft
in wake of the cold front with 850 mb temperatures around +5c will make
it feel like a crisp cool day at the surface with highs around the
upper-60s to low-70s...roughly 5 degrees below-normal. Scattered
diurnal cumulus around 5 kft across the interior /especially over the
high terrain/...sandwiched below a Stout dry-inversion.

Wednesday night...

Another night of high pressure with light / variable winds. Some
question as to whether conditions will remain clear. Possibility of
some high clouds filtering across the region ahead of a sharp cold
front diving S out of east-Canada /decent cyclonic flow and jet-
dynamics aloft/. This would limit radiational cooling and potential
fog development. Can not rule out some spotty areas of fog. Will
hold with the previous forecast of lows down into the 40s except
along the immediate coast.

&&

Long term /Thursday through Tuesday/...
big picture... upper trough over the northeast USA moves off by
Friday with the flow converting to zonal for Friday and Saturday.
Shortwave from the Gulf of Alaska merges with energy from the
Canadian Arctic late week while an upper ridge builds over the
Pacific coast. Both of these actions will dig an upper trough over
the Great Lakes...which moves into the northeast USA early next week.

Upper heights are below normal Thursday-Friday but moderate to 60
meters above normal by Sunday. This suggests a cool finish to the
week followed by a small warming trend over the weekend...then
cooling again by Tuesday as the upper trough and colder temperatures aloft
move back in.

The dailies...

Thursday... upper shortwave moves across southern New England and
pushes a weak secondary front through. Sufficient moisture for some
clouds especially north of the Mass Pike. But cold advection aloft
is weak as is instability...totals in the middle 40s and middle level
lapse rates a little over 5... we/re not big on convection.
Most likely a few showers. Temperatures at 850 mb 5-7c support maximum temperatures
middle 60s to lower 70s.

High pressure builds overhead Thursday night. Mostly clear skies and
light winds will allow radiational cooling. Dew points will be in
the 30s away from the coast and low 40s coast and islands. Expect
min temperatures 35-40 away from the coast and 40s along the coast. If mvy
Airport decouples...it will be near 40 or low 40s.

These temperatures will mean a potential for patchy frost. Mostly likely
areas would be southwest New Hampshire and northwest mass.

Friday-Saturday...high pressure over the region Friday shifts east
Saturday...but provides dry weather both days. Light winds
Friday...developing south wind Saturday. Model wind gusts for
Saturday do not reflect winds aloft in the mixed layer. So we bumped
values up to near 20 kts.

Friday temperatures aloft 0-2c supports maximum surface temperatures upper 50s to middle
60s...Saturday temperatures aloft 4-6c supports maximum surface temperatures middle 60s to
lower 70s. Radiational cooling again Friday night but dew points
will be a little higher...35-45...so min surface temperatures upper 30s and
40s. South winds will bring higher dew points Saturday night with
min temperatures upper 40s and 50s.

Sunday... increasing south wind Sunday with some increase in clouds
as a cold front approaches. But the day should remain dry with
plenty of sun. Model gust forecasts are again lower than the mixed
layer would suggest. Southwest winds show a gust potential to 25
knots and possibly as high as 30 knots. We bumped the Sunday wind
gusts up into the low 20s. Temperatures aloft around 10c and possibly to
12c. This means middle to upper 70s...and with sufficient mixing
there may be some spots with low 80s. Southwest wind may buffer
these values where it comes off the ocean.

Sunday night-Monday...cold front moves through our area early Monday
morning through midday. Best dynamics move from New York up through
Vermont. But sufficient low level convergence and moisture to
forecast showers with cold frontal passage.

Monday night-Tuesday...colder air advects in behind the cold front.
Meanwhile the upper trough moves east from the Great Lakes with
cooling temperatures aloft. Temperatures aloft 0-2c supporting upper 50s to middle
60s.

&&

Aviation /02z Wednesday through Sunday/...
forecaster confidence levels...

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

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

Tonight...
VFR through 2 am. After that...areas of IFR/LIFR ceilings/visibilities are
possible in locally dense fog. Best chance will be in the CT River
Valley in areas that received measurable rain earlier today.

Wednesday into Wednesday night...
IFR-LIFR fog Burns off in the morning. Few-scattered ceilings around 5 kft
for interior terminals. Sea-breezes along the shores towards
midday...eroding towards evening. Not enough confidence at this
time to believe there will be fog issues towards Thursday morning.

Kbos terminal...high confidence in taf. Variable-southeast will
become light west/northwest tonight.

Kbdl terminal...high confidence in taf. There is low confidence
of potential fog impacts towards Wednesday morning.

Outlook...Thursday through Sunday...high confidence.

VFR through the period. Southwest winds Saturday may gust to 20
knots. Southwest winds Sunday may gust 25 knots...possibly a little
higher.

&&

Marine...
forecaster confidence levels...

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

Short-term /through Wednesday night/...moderate confidence.

With Edouard...its intensity and proximity to southern New England
should result in long-period swell of around 14 seconds that
looks to remain at or below 5 feet.

With forecast guidance that has been overzealous with wave and
swell action with comparison to the latest buoy observations...
will hold off on the issuance of small craft advisories for
hazardous seas. It is certainly plausible towards midweek that the
outer waters will see 5 foot seas. This along with the long-
period swell...believe that the rip current risk will remain in
the moderate-range for the S-Atlantic facing shorelines negating
the need for rip current statements at this time.

Have greatest confidence with the ec wave model and wna-hurricane
wave guidance with respect to wave and swell action.

Outlook...Thursday through Sunday...moderate confidence.

Thursday... high pressure builds just north of the waters. North
winds 15 knots or less. Lingering 5 feet on the eastern outer waters
from swell...but this will be subsiding.

Friday...high pressure north of the waters will bring a stronger
northeast wind with potential for 20 knots especially around
Nantucket and on the southern outer waters. Seas will increase to 5-
7 feet in this northeast flow...diminishing as the winds diminish
Friday evening.

Saturday-Sunday...high pressure moves off through the Maritimes. The
winds will shift to south Saturday and southwest Sunday. Gusts to 20
knots both days with potential for 25 knot gusts on Sunday. Most
seas will remain below 5 feet...but the waters east of mass Bay and
Ipswich Bay may see seas rise again to around 5 feet.

&&

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

&&

$$
Synopsis...wtb/sipprell
near term...wtb/rlg/sipprell
short term...sipprell
long term...wtb
aviation...wtb/sipprell
marine...wtb/sipprell

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