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635
FXUS61 KBOX 111817
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
217 PM EDT Tue Jun 11 2024

.SYNOPSIS...
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Partly to mostly cloudy conditions to continue tonight and into
Wednesday as well. While most areas are dry on Wednesday,
isolated to widely scattered showers are possible during the
afternoon hours in eastern Massachusetts and Rhode Island. High
pressure moving off the coast will allow warmer temperatures
for Thursday and humidity by Friday. An approaching cold front
will bring the risk for scattered showers and thunderstorms
Friday afternoon and evening. High pressure builds in for the
weekend bringing beautiful dry weather with pleasant
temperatures and low humidity.
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&&

.NEAR TERM /THROUGH TONIGHT/...
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215 PM Update:

Satellite and observational analysis indicate models are
initializing the cold pool aloft associated with a broad upper
trough well this afternoon, with satellite showing partly to mostly
cloudy stratocumulus conditions. There could be a hit-or-miss shower
mainly in interior MA, CT and NW RI through sundown with PoP no
higher than 20% in any one area, but otherwise mostly cloudy and dry
weather should prevail. With the cloud cover, current temps are in
the upper 60s to lower 70s, on the cooler side for mid-June.

For tonight, any showers which developed should dissipate around
sundown. The main forecast challenge will be in regards to the
degree to which the existing cloud cover dissipates and how it would
impact low temps. Upper level trough responsible for the cloudiness
today slowly shifts eastward into much of interior VT/NH tonight, so
we`re still under its influence, even into Wed. All else being
equal, around sundown into the evening we see decreasing cloud cover
toward mostly clear conditions, but the presence of the upper trough
as well as lingering lower level RH around suggests siding the
forecast toward a partial cloudiness look vs going fully clear.
Temps are likely to be very tough; any areas which see sustained
breaks could cool off pretty well with light winds and others which
see continued or persistent cloudiness trend on the milder side.
Thus a pretty wide range of lows mainly in the 50s, but lower 50s in
the terrain and where skies can clear out, and upper 50s
elsewhere.
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&&

.SHORT TERM /WEDNESDAY THROUGH WEDNESDAY NIGHT/...
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215 PM Update:

Wednesday:

Although the upper-level low over New England is expected to pull
away from the Northeast later in the day, the forecast for Wed is
essentially similar to today. Residual cyclonic flow aloft and a
modifying cold pool should again support clouds filling back in with
a partial to mostly cloudy look, and that should also keep
temperatures from reaching into widespread low 80s as today`s NBM is
advertising. At least a lighter westerly flow could bring highs
closer to the upper 70s in western MA and much of northern CT
though, with highs in the lower to mid 70s for eastern/northeast MA
and much of RI.

Latest guidance seems a bit more bullish on isolated to scattered
shower chances Wed than today, as the east coast sea breeze
generates a mesoscale convergence zone in eastern MA/RI with the
lighter westerly flow across the interior. Dewpoints are also a
touch higher too over the coastal plain, and while the NAM`s
dewpoints still look a few degrees too high, values in the mid 50s
seem reasonable enough to yield surface based CAPEs of around 500
J/kg or less; phrased as isolated to scattered showers with 20-40%
PoP though as BUFKIT soundings from even the bullish NAM indicate
the layer of instability doesn`t reach into the -10C isothermal
layer for lightning. 12z HREF 1-hourly thunder probs are also
zero, with low probs confined to northern ME/NH closer to where
the upper low is progged. The risk for scattered showers should
be limited to just the MA/RI coastal plain around or within a
few miles either side of I-495; westerly non-convergent flow
further inland into CT and western MA should result in mainly
dry weather there. QPF amts likely no higher than a few
hundredths of an inch in any one area, so a few showers to dodge
but nothing too significant.

Wednesday Night:

Cloud cover with scattered light showers should dissipate shortly
after sundown towards mostly clear skies for the overnight.
Temperatures warm a bit aloft and that should help offset
radiational cooling to an extent with lows in the 50s, to low 60s in
the urban areas. With clear skies and light winds, there`s an
outside chance at patchy radiational fog, with somewhat better
chances of development where showers developed during the daytime
hrs.
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&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
Key Points...

* Dry but warm Thu with highs mainly middle to upper 80s
* Warm & Humid Fri with afternoon/eve scattered showers & t-storms
* Beautiful next weekend with low humidity & temps a tad below normal

Details...

Thursday...

Ridge of high pressure slides off the coast allowing warmer
southwest flow of air to develop across the region by Thu. 850T
warming to between +14C/+15C should allow afternoon highs to reach
the middle to upper 80s in many locations. Southwest winds will
result in somewhat cooler temps near the south coast...where 70s to
lower 80s will be more common. Humidity looks to remain in check Thu
and given mid level ridge axis crossing the region...dry weather
will prevail.

Friday...

Shortwave trough and an associated cold front will approach from the
west on Friday. Timing still somewhat uncertain...but expect
humidity to return ahead of an approaching shortwave/cold front.
Highs should reach well into the 80s to near 90 as long as we
receive enough solar insolation with dewpoints climbing into the
60s. Thinking at least some modest instability with 0-6 KM
shear increasing to between 40 and 50 knots. Enough forcing with
the shortwave should generate the development of scattered
showers & t-storms. Timing still uncertain this far out. We can
not rule out some elevated activity in the morning...but main
risk for scattered showers & thunderstorms will be during the
afternoon/evening hours. Given the parameters in place...we will
need to watch the risk for severe weather and localized heavy
rainfall with the activity. That being said...it is too early to
assess at this point but something to watch.

This Weekend...

Large Canadian high pressure builds in for the weekend. This brings
beautiful/dry weather for the weekend with low humidity and temps a
tad below normal. Highs will be 70s to near 80 with overnight lows
mainly in the 50s with even some upper 40s possible.

Monday....

High pressure moves off the coast on Monday...allowing for a return
southwest flow of warmer air to begin moving into the region. Upper
level ridging building north should result in dry weather continuing
too.

&&

.AVIATION /18Z TUESDAY THROUGH SATURDAY/...
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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.

Through 00z Tuesday: BKN-OVC VFR bases. A spot shower possible
mainly in interior CT/MA through sundown but coverage is too
sparse for a TAF mention and wouldn`t result in restrictions.
Light mainly W/NW winds, with seabreezes near the coasts.

Tonight: VFR continues with some SCT-BKN 040-060 bases around.
Winds light to calm, with eastern MA seabreezes turning onshore
by 00-01z and then beginning a clockwise turn to light WNW by
the pre-dawn Wed hrs. Radiational fog potential tonight viewed
as unlikely with more clouds cover around.

Wednesday: Mainly VFR, though SCT-OVC stratocu bases could
approach borderline MVFR levels at times. While the interior
airports should be dry, a lower to moderate (20-40%) chance at
a shower for BED, PVD and BOS during the aftn hours. Light W/WSW
winds in the interior, with seabreezes developing by 14-16z.

KBOS TAF...High confidence in TAF. BKN-OVC VFR bases this
afternoon, trending SCT tonight. Outside shot at a -SHRA thru 22z
but too unlikely to mention in TAF. Sea breeze kicks out
between 01z-03z with winds coming around to light WNW by pre-
dawn. Somewhat better chance at -SHRA or VCSH on Wed, with sea-
breezes starting around 15z.

KBDL TAF...High confidence in TAF. SCT-OVC VFR bases this aftn,
trending SCT tonight. Isolated shower possible but too unlikely
to mention in TAF. VFR bases return on Wed. Light W winds.

Outlook /Thursday through Saturday/...

Wednesday Night: VFR.

Thursday through Thursday Night: VFR. Breezy.

Friday: Mainly VFR, with local MVFR possible. Breezy. Chance
SHRA, isolated TSRA.

Friday Night: Mainly VFR, with local MVFR possible. Chance
SHRA, isolated TSRA.

Saturday: 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.

215 PM Update:

Winds and seas/waves to remain below small craft advisory
levels through this portion of the marine forecast period. Light
mainly southerly winds around 10 kt or less should be the rule
tonight through Wednesday night, though could turn easterly
nearest the shoreline with seabreezes. Seas mainly 3 ft or less,
with 1-2 ft seas near shore.

There could be a hit or miss shower Wed aftn near the
coastlines. Could see fog develop Wed evening over the outer
waters.

Outlook /Thursday through Saturday/...

Wednesday Night through Thursday: Winds less than 25 kt.

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

Friday: Winds less than 25 kt. Seas up to 5 ft. Chance of rain
showers, isolated thunderstorms.

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Rain showers likely, isolated thunderstorms.

Saturday: Winds less than 25 kt. Areas of seas approaching
5 ft.
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&&

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

&&

$$

SYNOPSIS...Loconto/Dooley
NEAR TERM...Loconto
SHORT TERM...Loconto
LONG TERM...Frank
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley