-- Discussion containing changed information from previous version are highlighted. --
239
FXUS61 KBOX 300553
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
153 AM EDT Thu May 30 2024

.SYNOPSIS...
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.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
Update: 10:20PM

Clouds are increasing SW/NE with leading edge of moderate rain
out over western Long Island and Stamford, CT. These showers are
slow moving, storm motion and speed based off neighboring KOKX
radar is 220 degrees at 15 knots. It will take some time before
these showers to reach southwest Hartford County - thinking
between 12am and 2am. Few showers out ahead of the primary zone
are possible, but likely will take some time before bulk of the
rain to reach eastern areas of the CWA, between 4am and 7am.

Previous forecast discussion below...

3 PM update...

* More widespread rain after midnight into THU AM

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.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM FRIDAY/...
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.

&&

.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
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.

&&

.AVIATION /06Z THURSDAY THROUGH MONDAY/...
-- Changed Discussion --
Forecast Confidence Levels:

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

06Z TAF Update: High confidence on trends, lower on exact
timing and details.

Through 12z... High confidence on trends, lower on exact
timing and details.

VFR with rain spreading in from southwest to northeast, CIGS
fall to MVFR 9z-12z south of the Mass Pike, with low end VFR
CIGS north. Widely isolated showers continue to bubble up ahead
of the main area of rain, added TEMPO group to site that could
see a brief shower with lower CIGS. Light winds will increase
around 12z and/or shortly after.

Today... High confidence on trends, lower on exact
timing and details.

Rain becoming widespread after 12z, MVFR/IFR CIGS for through
18z, rain tapers off from west to east with improving CIGS, it
will take some time for the I-95 corridor to lift from IFR to
MVFR, somewhere around 20z-22z. Gusty north/northeast winds are
10 to 20 knots.

Tonight... High confidence on trends, lower on exact
timing and details.

Lingering MVFR/IFR CIGS across Cape Cod and Nantucket, with a
low probability for a light rain shower. Otherwise, VFR CIGS
prevails along with dry weather. North/northwest winds are less
than 10 knots, while the coast winds are less than 15 knots.

Friday... High confidence.

Dry and VFR. Light northwest winds across the interior and
seabreeze along the coast.

KBOS TAF... High confidence in trends with moderate confidence
in timing.

CIGS are VFR early, becoming MVFR with widespread moderate rain
between 10z and 12z, likely a few hit and miss showers before
hand, have run a TEMPO for this chance. By 13z to 15z, IFR CIGS
and continued rain - which could become heavy at times. Winds
are north/northeast, gusting to 20 knots this morning into early
afternoon. MVFR conditions return after 18z with rain ending.
Could take some time for VFR CIGS to return, possible not until
21z to 23z. Becoming VFR with light northwest winds overnight.
VFR and dry on Friday with a likely seabreeze.

KBDL TAF... High confidence in trends with moderate confidence
in timing.

CIGS are VFR early, widespread rain arriving between 06z and 08z
and CIGS are falling shortly after to MVFR. Should maintain MVFR
CIGS this morning with moderate to at times heavy rainfall, the
rain continues through at least 12z to 14z with improvement to
VFR after 18z. North wind around 10 knots. VFR tonight into
Friday with dry conditions.

Outlook /Friday Night through Monday/...

VFR.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
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 Night 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.
-- End Changed Discussion --

&&

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

&&

$$

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