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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS61 KBOX 240803
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
403 AM EDT Sun Sep 24 2023

.SYNOPSIS...
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Spotty light rain and drizzle today will give way to a steady
rain, moderate to heavy at times tonight into Monday morning,
as the remnants of once tropical storm Ophelia track across the
area. Rain tapers off Monday afternoon from north to south, then
dry, but cool and brisk weather overspreads the region Monday
night and Tuesday, as large sprawling Quebec high pressure
builds into New England. Dry weather at mid week likely persist
into next weekend, along with moderating temperatures.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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Remnants of tropical storm Ophelia will be moving slowly north
across mid Atlc region today. Dry slot to the east has overspread
the region early this morning with just some spotty light rain. A
few t-storms have developed south of Long Island where there is
marginal instability but it is stable to the north so not expecting
any thunder this morning as this convection should weaken as it
moves north. Otherwise, expecting scattered showers moving north
across the region today as shortwaves rotate around the upper low.
Later today, deeper moisture plume associated with Ophelia remnants
begins to move into the region from the SW and may result in more
widespread showers south of the Mass Pike, with a focus across CT.
Also, a few late day t-storms can`t be ruled out across CT as some
instability aloft moves up from the south.

Weakening low level jet will lead to gradually diminishing winds
along the coast. NE winds 10-20 mph, with 20-30 mph gusts this
morning along the immediate south coast and Cape/Islands before
diminishing. Highs mostly in the low/mid 60s.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM MONDAY/...
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Tonight...

Remnants of Ophelia slowly moves east off the mid Atlc coast and
tracks south of New Eng. Deep moisture plume moves into SNE,
especially south of the Mass Pike. PWATs 1.5-1.75" combined with
modest synoptic forcing will bring numerous showers and isolated t-
storms south of the Mass Pike tonight. Locally heavy rainfall is
possible, with HREF and ensemble probs targeting CT for heaviest
rainfall. We will still be fighting dry air to the north so showers
should be more scattered north of the Mass Pike. Lows will be in the
50s.

Monday...

Deep moisture plume will remain in place to start the day on Monday
which suggests showers of varying intensity will continue,
especially south of the Pike. Drier air from the north will
eventually push southward into SNE which will bring a drying trend
from north to south in the afternoon, but wet weather will likely
persist all day across CT, RI and SE MA. Additional rainfall of 0.50
to 1 inch is possible south of the Pike through Monday, with
localized amounts of 1-2 inches possible with any heavier showers,
especially in CT. Decreasing rainfall amounts north of the Pike.
Cool day on Monday with rainfall and gusty NE Winds holding temps in
the upper 50s to lower 60s. Increasing low level jet as pressure
gradient increases will result in 20-30 mph gusts, strongest near
the coast.
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&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
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Highlights:

* Dry, brisk conditions overspread the region Monday night

* Sunshine & dry weather Tue into at least early next weekend

* Mild days and cool nights with highs in the 60s and lows in the
  40s, then moderating into the low 70s Friday & Saturday

Monday Night...

Post frontal airmass overspreads SNE as the remnants of Tropical
Storm Ophelia exit out to sea. Any lingering rain along the south
coast Monday evening will quickly give way to dry weather, as 1035
mb high over Quebec and associated dry airmass advects southward
into SNE. It will be windy especially across southeast MA, Cape Cod
and the Islands, as NE low level jet up to 35 kt streams across
relatively warm SSTs (60s), will promote gusty NE winds given steep
low level lapse rates.  As you would expect, a cool airmass
associated with the 1035 mb anticyclone, as 925 mb temps cool down
to about +7C by 12z Tue. Low level NE jet will keep blyr well mixed
and some airmass modification given SSTs in the 60s, precluding even
cooler temps. Lows in the 40s, except 50-55 along the coast given
winds off the relatively mild ocean.

Tuesday...

Dry but cool airmass over the region with 925 mb temps only +7C
across eastern MA to +9C over western MA/CT. This will only support
highs from around 60 along the eastern MA coast, to mid 60s across
western MA/CT, about 5-10 degs cooler than normal. It will feel even
cooler given gusty NE winds, especially over southeast MA. This NE
flow likely yields more clouds than sun in the morning, then
increasing sunshine in the afternoon as ensembles indicate anomalous
dry air associated with 1035+ mb Quebec high advecting south into
SNE.

Wednesday thru Saturday...

Anomalous Ridge Wednesday over Hudson Bay into southern Quebec,
slowly traverses eastward during this time period. Meanwhile, a low
amplitude closed low over the upper MS/OH valley advects eastward
and tries to undercut the ridge. As it does so, it deamplifies and
likely gets shunted to the Mid Atlc region, leaving SNE with dry
weather. Cool/dry airmass over the region provides splendid fall
weather, with sunshine and mild days, cool nights. Highs in the 60s
and lows in the 40s, but moderating with probability of highs in the
low 70s increasing Fri and Sat.
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&&

.AVIATION /08Z SUNDAY THROUGH THURSDAY/...
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Forecast Confidence Levels:

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

06z TAF update...

Through 12z...

Widespread MVFR/IFR conditions with spotty light rain. NE wind
gusts to 20-30 kt along immediate south coast and Cape/Islands

Today...Moderate Confidence.

Mostly IFR south of the Mass Pike with MVFR to the north.
Scattered showers becoming more widespread south of BAF-PVD
later in the day. NE winds 10-20 kt with some higher gusts along
the south coast.

Tonight...Moderate Confidence.

IFR conditions along and south of the Pike with numerous
showers. North of the Mass Pike, MVFR improving to VFR aft 06z
with scattered showers. NE wind 5-15 kt with increasing gusts to
20-25 kt south coast and Cape/Islands late tonight.

Monday...Moderate confidence.

MVFR south of the Mass Pike with a mix of MVFR/VFR to the north.
Scattered showers, mainly focused south of the Pike. NE wind
10-20 kt with gusts to 25 kt along the coast and up to 30 kt
over the Islands.

KBOS TAF...Moderate confidence.

Mainly MVFR cigs through the period, although can`t rule out
some IFR through the morning. Scattered showers. Cigs may
improve to VFR late tonight as some drier air tries to move in
from the north. NE gusts to 20 kt today.

KBDL TAF... Moderate confidence.

IFR may temporarily improve to VFR later this morning before
dropping back to IFR tonight. More widespread showers developing
later today through tonight.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday: Mainly VFR, with local MVFR
possible. Windy with local gusts up to 30 kt.

Tuesday Night through Thursday: VFR. Breezy.
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&&

.MARINE...
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Forecaster Confidence Levels:

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

Winds will gradually diminish through today as low level jet
weakens, with 20-25 kt gusts by this afternoon. Winds ramp up
again late tonight and especially Monday as low level jet
increases. Gusts to 25-35 kt are expected Monday with the
strongest gusts over the south coastal waters. Gale warnings may
be needed if confidence increases for 35 kt gusts. Vsbys will be
reduced at times in occasional rain and fog through Monday.

Outlook /Monday Night through Thursday/...

Monday Night through Tuesday: Moderate risk for Small Craft
Advisory winds with gusts up to 30 kt. Rough seas up to 8 ft.

Tuesday Night through Wednesday: Low risk for Small Craft
Advisory winds with gusts up to 25 kt. Seas up to 5 ft.

Wednesday Night: Winds less than 25 kt. Areas of seas
approaching 5 ft.

Thursday: Winds less than 25 kt. Seas up to 5 ft.
-- End Changed Discussion --

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
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CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until noon EDT today for ANZ230.
     Small Craft Advisory until 2 PM EDT this afternoon for ANZ231-
     236.
     Small Craft Advisory until 8 AM EDT Monday for ANZ232>235-237-
     250-251-254>256.
-- End Changed Discussion --

&&

$$
SYNOPSIS...KJC/Nocera
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...Nocera
AVIATION...KJC/Nocera
MARINE...KJC/Nocera