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208
FXUS61 KBOX 291854
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
254 PM EDT Wed May 29 2024

.SYNOPSIS...
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Other than a few brief showers/thunderstorms this afternoon and
early evening, mainly dry, pleasant warm weather prevails. Low
pressure then brings a more widespread rain, moderate to heavy at
times later tonight into Thursday morning, then slowly dries out
Thursday afternoon from west to east. Drier weather with plentiful
sunshine for Friday. After a few days of temperatures at or slightly
cooler than normal, the weekend into Monday offers a warming trend
toward above normal temperatures and still tolerable humidity
levels. Drier weather should generally prevail this weekend into at
least Tuesday.
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&&

.NEAR TERM /UNTIL 6 AM THURSDAY MORNING/...

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3 PM update...

* Other than a few showers/isolated thunderstorm, mainly dry this
  afternoon and early evening

* More widespread rain after midnight into THU AM

This afternoon & early evening...

12z models have trended drier for this afternoon and early evening,
as it appears there will be more than expected subsidence over SNE
between departing s/wv exiting ME and approaching s/wv currently
over southwest PA. Thus, shower/thunderstorm activity is expected to
be more isolated (not widespread).  Radar beginning to pickup some
scattered showers entering western MA/CT.

Still low risk of an isolated storm with small hail and brief heavy
downpours in the stronger cells. Otherwise, just lots of diurnal
scu/cu today given the cyclonic flow and cold air aloft (-18C at 500
mb). Despite the steep mid level lapse rates, diurnal buildups out
the window here and on satellite, is limited given dew pts only in
the upper 40s and lower 50s. These low dew pts yielding very
pleasant conditions for late May, with low humidity and temps
slightly warmer than normal, as highs climb into the mid/upper 70s
away from the coastline.

Overnight...

Mainly dry this evening (after any diurnal showers/thunderstorms
dissipate), then bands of rain overspread the region later tonight
and become fairly widespread. This is in response to a potent s/wv
currently over southwest PA advects eastward. In fact, models are
suggesting this will take on more of a cool season rain event, as
s/wv is fairly baroclinic for late spring, with mid level Fgen
around 850 mb. In addition, models are hinting at some instability
above this layer and the response is for bands of moderate to heavy
rain. This already is present on radars across PA. Exact location of
these bands as they traverse SNE varies from model to model, ranging
from northern MA to the south coast. This instability may be
sufficient for isolated thunder, but more likely, enhancing rainfall
potential, with moderate to heavy rain at times late tonight and
towards Thu morning. Seasonably cool tonight with lows in the 50s.
Light and variable winds become NE toward morning and may become
gusty 15-20 mph towards morning, as surface wave develops along or
just offshore.
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&&

.SHORT TERM /6 AM THURSDAY MORNING THROUGH THURSDAY NIGHT/...

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3 PM update...

Highlights:

* Bands of moderate to heavy rain THU AM
* Drying trend Thu PM from west to east
* Cooler given cold temps aloft

Thursday...

As mentioned in the short term section above, baroclinic s/wv and
attending surface low move across SNE Thu AM. 850 mb Fgen and weak
instability above this layer will yield bands of moderate to heavy
rain at times. Widespread rainfall totals of 0.25 to 0.75 inches,
with local amounts possibly 1+ inches. Could be a slow AM commute
given periods of moderate to heavy rain yielding minor
street/highway flooding.

Mid level trough axis moves east of the region after 18z along with
dry slot ovespreading the area. Thus, drying trends in the afternoon
from west to east, along with a breaks of sunshine possible,
especially late in the day. Much cooler tomorrow given cold pool
aloft, combined with NNE onshore flow along with precip in the AM.
Highs only in the 60s. Coolest along the eastern MA coastline,
especially with NNE winds 15-20 mph providing cool/damp/raw
conditions. Highs closer to 70 in the CT River Valley, including
Hartford and Springfield.

Thursday night...

Mainly dry weather, although clouds and spotty light rain/drizzle
may linger across the outer Cape to Nantucket given moist NNE flow.
Otherwise, dry and cool weather with lows 45-50 most of the region.
Given the cooler regime, we blended in some of the cooler MOS
guidance to derive min temps.
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&&

.LONG TERM /FRIDAY THROUGH WEDNESDAY/...

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3 PM update...

Highlights

* High pressure supports mostly dry/quiet weather through the
  middle of next week

* Temperatures gradually increasing through the middle of next week

Through Next Wednesday

The extended forecast looks to be very quiet from Friday forward as
a broad upper-level ridge builds in behind a departing short-wave
trough on Friday afternoon. This will support high pressure at the
surface that will support mainly dry/sunny conditions through at
least early next week. Temperatures will be on the uptick through
this time range as well with seasonable temperatures on Friday in
the low to mid 70s gradually increasing to the mid 80s by next
Tuesday. Low temps will follow a similar pattern with lows in the
upper 40s/low 50s Friday night increasing to the low 60s by
Wednesday morning. The upper level ridge supporting this pattern
looks to possibly breakdown mid to late next week with a potentially
robust upper trough digging down from The Great Lakes. This would be
the next possibility for any active/unsettled weather beyond Friday.
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&&

.AVIATION /19Z WEDNESDAY THROUGH MONDAY/...
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Forecast Confidence Levels:

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

18z TAF Update: high confidence on trends, lower on exact timing and
details.

Through 00z...high confidence.

VFR and mainly dry. Less than 30% chance of a few showers and
isolated thunderstorm thru 00z. Light NW winds except light onshore
near the coast.

After 00z...high confidence, lower on exact timing of details.

VFR and mainly dry, then lowering conditions after midnight to MVFR
as a widespread rain overspreads the region. Light and variable
winds this evening becoming NNE overnight and increasing 10-20 kt.

Thursday...high confidence, lower on exact timing of details.

MVFR in widespread rain in the morning, low probability of IFR over
southeast MA.  Then rain shield slowly exits in the afternoon with
slow improvement to VFR from west to east. NNE winds 10-20 kt.

Thursday night...high confidence, lower on exact timing of details.

MVFR/IFR may linger across Cape Cod and Nantucket. Otherwise, VFR
prevails along with dry weather. NNE winds 10-15 kt.

KBOS TAF...Moderate confidence in TAF. Other than an isolated shower
this evening, VFR and dry weather. Then lowering conditions after
midnight to MVFR with large rain shield overspreading the terminal.
Periods of moderate to heavy rain from 06z to 18z Thu. Drying trend
and improvement for the late day push Thu.

KBDL TAF...Moderate confidence in TAF. Isolated shower thru 00z.
Otherwise VFR. MVFR with rain after 03z and continuing until about
15z Thu. Then slow improvement thereafter.

Outlook /Friday through Monday/...

VFR.
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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.

3 PM update...

Tonight...mainly dry and good vsby this evening, then rain
overspreads the waters after midnight. Light onshore winds become
NNE overnight, 15-20 kt.

Thursday...weak/broad low pressure moves over or just offshore, with
NNE winds 15-20 kt across the MA/RI waters, along with reduced vsby
in rain in the morning.  Then slow improvement west to east in the
afternoon.

Thursday night...NNE winds 10-15 kt may yield spotty light
rain/drizzle across the eastern MA waters. Otherwise, dry weather
and good vsby for the RI waters.

Outlook /Friday through Monday/...

Friday through Sunday: Winds less than 25 kt.

Sunday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Monday: Winds less than 25 kt.
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&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...None.

&&

$$

SYNOPSIS...Nocera/RM
NEAR TERM...Nocera
SHORT TERM...Nocera
LONG TERM...RM
AVIATION...Nocera/RM
MARINE...Nocera/RM