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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
1028 am EDT Tue Sep 17 2019

Synopsis...
expect a quiet spell of weather through the week with mild days
and cool nights. There is a spot chance of a shower tonight
into Wednesday, but a dry forecast for most people/areas.
Temperatures warm up late week into the weekend. Dangerous surf
and rip currents will develop along ocean facing beaches due to
well-offshore Humberto. The next best chance at any rainfall in
the form of showers is forecast for early next week.

&&

Near term /through tonight/...

High pressure over eastern Canada is building over southern New
England. This will turn winds from the northeast and east
during the afternoon over eastern Massachusetts and Rhode Island and the central
hills, while CT and western Massachusetts remain more northerly.

An area of cloud-level moisture moves into northeast Massachusetts later
this afternoon. This may be enough to generate partly cloudy
skies, mainly from the Merrimack River to Boston.

Temps aloft are forecast at 5c east to 7c west, supporting Max
temps in the mid 60s to lower 70s.

&&

Short term /Wednesday/...
onshore flow continues tonight into Wednesday. Colder air will
continue to flow into our region, with Wednesday probably being
the coldest day this week. As temperatures lower, expecting
marine stratus to develop and move onshore. The layer of higher
moisture content is rather shallow beneath a substantial
subsidence inversion. Temperature differential for ocean
enhancement is impressive for mid September. There may be a few
sprinkles to contend with tonight into Wednesday morning.

&&

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

- mild days, cool nights through the week, dry throughout
- turning warmer over the weekend into next week
- next chance of rain may not be till early next week

*/ overview...

Transitioning warmer? Mild days, cool nights through the week but by
the weekend into the following week we could see warmer than average
conditions. Positive teleconnections across the board minus the pna.
Wpo/epo strongest into late September signaling a strong Pacific jet
into western North America. Mid-latitude energy downsheared across the west
Continental U.S. As a prominent mjo is forecast over the west hemisphere / Africa
(phase 1/8), the potential combination North Atlantic tropical waves /
latent heat release with favorable downstream east Continental U.S. Ridging from
an onshore mild Pacific jet supports warmer than average conditions
advertised by CPC 6-10 / 8-14 day outlooks. All signs point towards
higher heights late September across New England. With that there
does not seem to be much rainfall opportunity. Ensembles showing out
through the rest of the month there's an SW-NE east Continental U.S. Axis into S
New England of less than an inch of total rainfall. Deterministic
forecast guidance highlights our next best chance of rainfall early
the following week. Looks like we're in store for a long period of
dry weather which is not atypical as September is one of more drier
months on average. Neither is warmer than average temperatures. A
glance back at records for late September, we've observed upper 80s
to low 90s for highs.

An ensemble blend forecast with lower certainty on specifics further
out in the forecast. Warming trend into the weekend as high pressure
shifts east and S/SW winds prevail prior to a sweeping cold front early
the following week with a chance of showers. Could see a brief cool
down thereafter before warmer weather builds back in as we go into
autumn.

&&

Aviation /14z 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/...

This afternoon... VFR, with cloud bases around 4000 feet. Best
chance for clouds will be around the Merrimack valley and
Boston. North wind becoming NE at 5 to 15 kt. Gusts up to 20 kt may
occur across the cape and islands by mid to late afternoon.

Tonight and Wednesday...
mainly VFR. A period of broken 020-030 MVFR ceilings along with a
passing rain showers or two possible across portions of east Massachusetts tonight into
Wednesday morning. Lower MVFR possible along the high terrain down
to 010.

Kbos terminal...
high confidence in taf. 020 MVFR possible tonight into Wednesday.

Kbdl terminal...
high confidence in taf.

Outlook /Wednesday night through Saturday/...

Wednesday night through thursday: VFR. Breezy.

Thursday night through saturday: VFR.

&&

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.

This afternoon... north/NE wind with afternoon gusts up to 20
knots. Seas 2-4 ft.

Tonight and Wednesday...
NE wind gusts around 20 knots at times in the cool air advection
pattern. Gusts increasing up to around 25 kt Wednesday afternoon.
Seas increasing 3-5 ft by early Wednesday morning across the
open waters. Will need to consider small craft advisories with
later forecasts.

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

Wednesday night: low risk for Small Craft Advisory winds with
gusts up to 25 kt. Areas of rough seas.

Thursday through Thursday night: winds less than 25 kt. Local
rough seas.

Friday through Friday night: winds less than 25 kt. Rough seas
up to 10 ft.

Saturday: winds less than 25 kt. Areas of rough seas.

&&

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

&&

$$
Synopsis...Belk/sipprell
near term...wtb/Belk/sipprell

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