-- Discussion containing changed information from previous version are highlighted. --
979
FXUS61 KBOX 250222
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1022 PM EDT Fri May 24 2024

.SYNOPSIS...
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Warm and mostly dry conditions this weekend, but a few afternoon
thunderstorms are possible Sunday. A slow moving front may bring
significant rainfall Monday afternoon into Monday night. Drying
out Tuesday, then unsettled weather pattern sets up again from
mid week into next weekend with cooler temperatures.
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&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
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No significant changes to the forecast this evening. A weak
secondary cold front was almost completely past southern New
England. As of this writing, this front was located from around
Marshfield, to just north of Warwick, to just north of the CT
coast. Drier air behind this front, so once it passes by, dew
points in the lower to mid 40s should prevent the formation of
stratus and fog later tonight. Brought temperatures back in line
with observed trends.

Previous Discussion...

Cold front across northern New Eng will push south into SNE this
evening and move off the south coast overnight. Dry frontal
passage as moisture and convergence is limited. Just an area of
enhanced cloud cover along the front but these clouds will
diminish as they approach SNE. Looking at mainly clear skies
tonight with diminishing wind this evening then turning light
north behind the boundary later tonight. Decent cooling develops
overnight with lows dropping to low-mid 50s, but upper 40s in
colder locations in western MA and possibly interior E MA.
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&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH SATURDAY NIGHT/...
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Saturday...

High pres will be in control with abundant sunshine during the
morning, then high clouds will be increasing during the
afternoon as mid-high level moisture begins to increase from the
west. Slightly cooler airmass Sat with 925 mb temps 16-18C
leading to highs mostly in the 70s, but lower 80s more likely in
the CT valley and Merrimack valley. Sea-breezes will develop
holding temps in the upper 60s and lower 70s near the immediate
coast and Cape Cod.

Saturday night...

A modest W-SW low level jet will transport higher moisture into
SNE as PWATs increase to around 1.25". Some weak elevated
instability also develops which may lead to a few showers
developing in the interior, but area coverage will likely be
limited. Lows will be in the 50s.
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&&

.LONG TERM /SUNDAY THROUGH FRIDAY/...
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Highlights

* Mix of sun and clouds on Sunday with some afternoon
  thunderstorms possible

* Substantial rain event Monday afternoon into Tuesday morning

* After a brief dry out Tuesday into Wednesday morning, an
  unsettled weather pattern looks to dominate the Northeast for
  the foreseeable future

Sunday

High pressure shifts to the east on Sunday allowing south winds
to advect higher dewpoints into southern New England. As a
result, increased low-level moisture will result in more cloud
cover than the previous two days, but there should still be a
good amount of sunshine for most of the day as well. Background
wind field may be weak enough to support a sea-breeze along the
coastline. Model forecast soundings suggest a fair amount of
instability may be available on Sunday to support thunderstorm
development in the afternoon. Deep layer moisture is forecast to
be lacking across most of the areas west of I-495, but model
guidance suggests more mid- level moisture availability across
eastern MA. If a sea-breeze boundary develops, low/mid-level
lapse rates, sufficient instability, and up to 30 knots of deep
layer shear would likely be enough to support a few afternoon
thunderstorms with a sea-breeze boundary providing the necessary
lift. Only FV3 and NAMNest Hi-Res models are available at this
time as they extend out to 60 hours, and each are resolving
convection over southern New England Sunday afternoon. More
details will become available as the rest of the HREF members
and their 48 hours become available tonight and tomorrow. Temps
will be upper 70s/low 80s across the interior and cooler along
the coast in the upper 60s/low 70s.

Monday and Tuesday

Substantial rainfall is likely Monday afternoon into Tuesday
morning as a low-pressure system moves across The Midwest/Great
Lakes region. Monday looks to feature mainly overcast skies and
periods of warm frontal precipitation. As moisture increases
ahead of the associated cold front Monday night into Tuesday,
more substantial rainfall is likely Monday night into Tuesday
morning with PWATs up to 1.75" potentially supporting rainfall
accumulations of an inch or greater by Tuesday morning. The
consensus among latest guidance is for a dry slot to work its
way over the region by late Tuesday morning/early Tuesday
afternoon to allow for a salvageable spring day on Tuesday.

Wednesday and beyond

By mid-week a second upper-level disturbance will dig down from
The Midwest and settle over The Northeast. A near -20 Celsius
upper cold pool at 500 hPa looks to become quasi stationary over
The Northeast through the end of next week. This will support
unsettled weather and below normal temperatures that may persist
through the end of next weekend.
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&&

.AVIATION /02Z SATURDAY THROUGH WEDNESDAY/...
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Forecast Confidence Levels:

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

Tonight...High confidence.

VFR, but patchy stratus/fog may impact ACK late this evening.
W-SW gusts to 25 kt diminishing this evening and becoming light
N overnight.

Saturday...High confidence.

VFR. S-SW wind near 10 kt developing Sat afternoon with sea-
breezes along the coast.

Saturday night...Moderate confidence.

Mainly VFR, but patchy MVFR-IFR stratus and fog possible
overnight. Areal coverage of lower conditions is uncertain.
A few showers possible in the interior.

KBOS TAF...High confidence in TAF.

KBDL TAF...High confidence in TAF.

Outlook /Sunday through Wednesday/...

Sunday: VFR. Slight chance SHRA, isolated TSRA.

Sunday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA, isolated TSRA.

Memorial Day: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA.

Monday Night: MVFR/IFR conditions possible. Breezy. SHRA
likely, isolated TSRA.

Tuesday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA.

Tuesday Night through Wednesday: VFR. Slight chance SHRA.
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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.

Through Saturday night...High Confidence.

A few G25 kt over eastern MA nearshore waters this afternoon,
then winds diminish this evening becoming light N overnight.
Light winds Sat morning becoming S-SW 10-15 kt Sat afternoon and
night. Seas below SCA.

Outlook /Sunday through Wednesday/...

Sunday: Winds less than 25 kt. Slight chance of rain showers.

Sunday Night: Winds less than 25 kt.

Memorial Day: Winds less than 25 kt. Slight chance of rain
showers.

Monday Night through Tuesday: Winds less than 25 kt. Seas up to
5 ft. Chance of rain showers, isolated thunderstorms.

Tuesday Night: Winds less than 25 kt. Seas up to 5 ft. Slight
chance of rain showers.

Wednesday: Winds less than 25 kt. Areas of seas approaching
5 ft. Slight chance of rain showers.
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&&

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

&&

$$

SYNOPSIS...KJC/RM
NEAR TERM...Belk/KJC
SHORT TERM...KJC
LONG TERM...RM
AVIATION...KJC/RM
MARINE...KJC/RM