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Area forecast discussion
National Weather Service Boston/Norton Massachusetts
227 am EDT Sat Sep 21 2019

Synopsis...
high pressure remains in control into Monday with Summer-like
temperatures and dry weather. A cold front will bring a period
of showers late Monday and Monday night followed by cooler, but
seasonably warm, weather through the rest of next week.

&&

Near term /through today/...
dry weather continues with high pressure centered to our south.
Light westerly winds will become light south to southwest
across the interior. A different story towards the coast, where
the combination of above normal temperatures and light winds
will lead to seabreezes. Max temperatures today should be a few
degrees higher than Friday, even towards the coast.

While the swell from Hurricane Humberto will be subsiding, it
will not be entirely gone. Still an elevated risk for rip
currents Saturday. If going to the beach this weekend, be
especially cautious if there are no lifeguards present.

&&

Short term /tonight through 6 PM Sunday/...
dry weather tonight into Sunday. The warming trend continues
with a high pressure off to our southeast producing an
increasing southwest wind. Above normal temperatures through
this period.

&&

Long term /Sunday night through Friday/...

*/ highlights...

- rain anticipated late Monday into Monday night
- thereafter mild days, cool nights, dry the remainder of the
week
- temperatures running above average throughout

*/ overview...

Amplifying pattern. Impressive North Pacific jet signaled by a
+wpo/+epo that Cascades energy and mild air over the Continental U.S.
Initially. Kicking downsheared energy across the 4-corners
region, a closing mid-level low latched onto Continental
moisture, there's a chance for rainfall around Monday night
discussed in more detail below. However by late September a
pattern-amplification emerges. One-two punch, northwest Pacific Tapah
becoming Post-tropical, ingested into the Bering straight low,
subsequent latent heat release amplifies the longwave trof that
re- captures earlier cut-off North Pacific energy. Heightened Alaska
Ridge that ultimately downshears a deep trof across the west Continental U.S.
Into the end of September, pna becomes largely negative as does
the epo/wpo. With a continued active North Atlantic tropics
emphasized by the phase 1 mjo, an impressive heat pump and
anomalously higher heights emerge over the east Continental U.S.. no surprise
to see above average temperature trends and below average
precipitation per CPC. However along the NE-periphery of the
heat-bubble no-trouble, there are opportunities for cooler air
and rainfall chances along southeast-sweeping cold front boundaries. So
not entirely convinced we'll see the brunt of the heat expected
for the southeast Continental U.S. North into the mid-Atlantic. Perhaps just on the
cusp yet however for late September is still above average when
highs are normally around 70 and lows normally around 50. A
pattern of mild days and cool nights, some shots of wet-weather
in-between. Break down the details below.

*/ Discussion...

Monday into Monday night...

Widespread showers and appreciable rainfall remains possible.
Lean towards wetter solutions given consensus forecast mid-level
closed- low solution acting on a narrow-ribbon of Continental
moisture. Much of the same, precipitable waters up around
1.75-inches, warm-cloud layer up around 12 kft preceding the
sweeping cold front. A moist- adiabatic, conditionally-unstable
profile, albeit brief and right along the front, expected lift,
low-level convergent forcing, and synoptic ascent beneath
cyclonic flow and diffluence aloft makes a case of decent upward
motions that should promote collision as well as coalescence
such that decent rains should develop. Positive to a neutral
tilt trof with modest west/SW shear preceding, instability is in
question given marginal, moist-adiabatic lapse rates. Rumbles of
thunder not ruled out, nor heavier downpours. Chance to likely
pops. There's increasing signal of the possibility of
significant rainfall with amounts around 0.50 inches.

Rest of the week...

Rain chances around Thursday night appear suppressed by the
weight of increasing heights across the east Continental U.S.. however with
the prior mentioned amplified pattern tightening over the west and
central Continental U.S. That New England finds itself beneath northwest flow
aloft, the opportunity for some slightly cooler air and rainfall
chances along southeast sweeping cold fronts over the weekend into
early next week. However overall temperatures still look to run
above average.

&&

Aviation /06z Saturday through Wednesday/...
forecaster confidence levels...

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

Short term /through Sunday/...high confidence.

VFR to continue though Sunday. Generally light west winds today
across the interior. Seabreezes developing by midday along the
coasts, impacting coastal terminals. Isolated IFR in low clouds
and fog for portions of the CT River Valley around kore this
morning.

Kbos terminal...high confidence in taf.

Kbdl terminal...high confidence in taf.

Outlook /Sunday night through Wednesday/...

Sunday night: VFR. Breezy.

Monday: mainly VFR, with local MVFR possible. Breezy. Slight
chance rain showers.

Monday night: mainly MVFR, with areas VFR possible. Breezy.
Chance rain showers.

Tuesday: mainly VFR, with areas MVFR possible. Chance rain showers.

Tuesday night through wednesday: VFR.

&&

Marine...
forecaster confidence levels...

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

Short term /through Sunday/...high confidence.

Adjusted the timing of small craft advisories for today. Swell
from Hurricane Humberto will continue to diminish through the
day. Relatively light winds will mean smaller wind waves. Local
seabreezes near the coast today. Relatively tranquil winds and
seas expected tonight into Sunday, with light S to SW winds.

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

Sunday night: winds less than 25 kt. Areas of seas approaching
5 ft.

Monday: low risk for Small Craft Advisory winds with gusts up
to 25 kt. Local rough seas.

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

Tuesday: winds less than 25 kt. Local rough seas. Chance of
rain showers, patchy fog.

Tuesday night through wednesday: winds less than 25 kt. Areas
of seas approaching 5 ft.

&&

Box watches/warnings/advisories...
CT...none.
Massachusetts...none.
Rhode Island...none.
Marine...Small Craft Advisory until 11 am EDT this morning for anz250-
254-255.
Small Craft Advisory until 5 am EDT early this morning for
anz251-256.

&&

$$
Synopsis...Belk/sipprell

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