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361
FXUS61 KBOX 040722
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
322 AM EDT Thu Jul 4 2024

.SYNOPSIS...
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Increasing clouds and humidity levels today, and while there
could be an isolated shower or thundershower in western MA and
CT this afternoon, many stay dry. A better chance for showers
or storms exists later tonight and overnight, with lesser
chances for showers or storms on Friday. Very warm and humid
conditions will continue this weekend through early next week.
Best chance for rain comes Friday night through Saturday night.
There will be dry periods, and will not rain continuously.
Sunday though Monday is warm, humid, and dry. A return to more
unsettled weather Tuesday and Wednesday.
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&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
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315 AM Update:

Key Points:

* Increasing clouds and turning more humid today

* Best chance at isolated showers, possible rumble of thunder in
  western and central MA and northern CT after 2 PM today, but
  many stay dry during the daytime hrs.

Good morning and Happy Fourth of July! Broad high pressure remains
anchored over the southeastern offshore waters early this morning.
Ridging from it is maintaining dry weather and a light SW flow
for most, although winds are calm for the RI/MA South Coast.
Rising dewpoints into the lower to mid 60s along the immediate
coastline has allowed for patches of stratus and mist to
develop, although it hasn`t been very persistent to this point
in the early morning. To the north and west is a weak surface
trough which trails from Lake Champlain southwest thru western
NY. This surface feature is embedded within a broad WSW flow
aloft which extends all the way into the Central Plains states.
Current temps are in the 60s for most as of early this morning
with an increasing stream of high clouds.

For today, we find ourselves in a weak pressure pattern with a
sagging surface trough gradually moving into an increasingly more
humid air mass. Being frank, in this weakly forced setting,
confidence in the potential for showers or rumbles of thunder and
the timing thereof is lower than average, with varied answers across
the higher-resolution guidance, sometimes across hourly-updated
model runs. I do think most of the morning is dry as higher
dewpoints haven`t really increased. But south winds will gradually
advect in mid to upper 60s dewpoints this afternoon, and that raises
the potential for isolated showers later this afternoon; think the
locations with the best chance at isolated showers is mainly from a
Fitchburg to Worcester to Willimantic line westward after 2 PM. With
increasing cloud cover today leading to poor heating/lapse rates,
instability parameters are also pretty poor with lifted indices
around 0 to -1, weakly unstable. Honestly wrestled a bit with
how to phrase shower chances today, as many will likely be
outdoors today and I really can`t see the risk for showers being
high. Instead of probability wording, I opted for isolated
showers with a mention of thunder for the interior CT/MA areas
to at least get the message out that there should be showers to
dodge; but the coverage looks sparse and dry weather should
prevail most of the time. It`s really not until tonight when
there`s a somewhat better chance for showers. Further east, we
should just see increased cloud cover but the daytime hours are
largely dry.

Should see some heating today but with increasing clouds, expect a
slower rise in temps into the afternoon. Opted for highs in the
lower to mid 80s, although SW breezes along the south coast will
keep highs closer to the mid to upper 70s. It will also start to
feel pretty muggy this afternoon as dewpoints rise more
substantially.
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&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
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315 AM Update:

Tonight:

Surface trough continues to sag southward to our southern coastal
areas, though it either stalls out and/or washes out as it does so.
At the same time, a weak shortwave impulse over part of the mid-MS
Valley early this morning will have moved into southern NY/PA by
tonight. This feature will have rising moisture levels to act on
(PWATs rise to 2-2.25 inches per the 03z SREF!) and with the weak
boundary nearby, we should see a better chance for scattered showers
tonight mainly south of the Mass Pike, with lower/lesser chances
north of the Mass Pike. Best chance at showers/possible embedded
thundershowers before midnight is in CT, but confidence in the
timing is far from the strongest and is subject to further
adjustments. Not talking heavy rain or flooding with this, but
with the really juiced environment even showers could bring
some brief downpours as warm cloud depths are around 14,000 ft.

SW winds weaken overnight to light and variable, and creates an
environment which could favor mist/fog development with the rising
humidity levels. With overcast around tonight, sided temps toward
warmer guidance in the upper 60s to low 70s, with dewpoints in the
upper 60s.

Friday:

Timing uncertainties associated with the weak disturbance moving in
later tonight cast lingering uncertainty for Friday too. With that
said, we`ll have a stalled frontal boundary in our southern
waters which will keep the immediate south coast unsettled.
Further north and west, more clearing should allow for somewhat
greater heating/destabilization with CAPEs around 500-1000 J/kg.
With the very humid air mass, it won`t take much heating to pop
up a shower or garden variety storm mainly north and west of
I-95, but background weak subsidence aloft and weak 500 mb
height rises in the wake of the passing weak disturbance from
overnight tonight should keep coverage to a minimum. So,
continued partly to mostly cloudy conditions with PoPs in the
15-20% range. Friday feels quite warm and humid with highs in
the mid to upper 80s with dewpoints in the 70s, supporting heat
indices in the upper 80s-low 90s. Cooler along the southeast
coast where cloud cover will be slower to disperse, with highs
in the upper 70s/lower 80s but still humid.
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&&

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

* Few showers possible on Friday, otherwise dry, warm and muggy.

* Elevated humidity Saturday along with the potential for heavier
  rains and an isolated afternoon thunderstorm or two.

* Warm and muggy Sunday into Monday, although trends are looking
  drier both days. Unsettled conditions return Tuesday into
  Wednesday.

Friday Night into Saturday Night:

Unsettled and down right muggy conditions heading into the upcoming
weekend. Overnight into Saturday morning shortwave energy ejects out
of the Great Lakes leading to scattered rain showers overnight and
ending Saturday morning as the best mid-level forcing exits east of
southern New England by mid morning. Warm and quite muggy with dews
in the low to middle 70s Saturday afternoon, with highs between the
low and middle 80s there is enough surface based instability, around
1,000 J/kg to get a few showers to develop. Lapse rates are rather
poor with the best low-level lapse rates west of the Berkshires
between 7-8 C/km and the mid-level lapse rates are less than 6 C/km.

Any showers or thunderstorms that do go up will have the potential
to produce heavy rains. There is plenty of moisture to be had, as
mentioned the past several nights PWATS are well above 2 inches, and
per 04/00z guidance, those values are still on track to be between
2.0" and 2.5", daily climo max per the soundings archive is around
2.05", with the max of all soundings at 2.73" for CHH. And with a
warm cloud layer of ~13,000 feet, there is the potential for
efficient rain makers.

Robust mid-level shortwave north of the eastern Great Lakes in
Canada moves east overnight with shortwave energy breaking off and
passing through New England, still looks like the best lift will be
northern New England, but there could be enough lifts that makes it
way south to promote showers overnight as well.

Sunday trough Wednesday:

Southern New England is still on the outer periphery of a mid-level
ridge that is anchored over Bermuda. While not as humid on Sunday,
dews remain in the upper 60s to near 70 degrees, plus temperatures
in the middle and upper 80s, closer to 90 in places like Springfield
to Hartford. Right now, there is little mid-level forcing to get any
showers going, plus BUFKIT sounding show a firm CAP so think the day
will feature mainly dry conditions. Monday looks to be a carbon
copy.

More unsettled conditions into mid week with the mid-level ridge
shifting south and a trough approaching from the west, this will
usher in the next round of rain and thunderstorms. Mid 80s to low
90s on Tuesday, then low to mid 80s on Wednesday.
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&&

.AVIATION /07Z THURSDAY THROUGH MONDAY/...
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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 Thursday: High confidence.

Largely VFR; can`t rule out a brief period of IFR-visby fog for
the Cape and Islands thru 10z. Offered TEMPO 1 SM BR for these
TAFs. Light south winds, calm at times especially SE MA.

Today: High confidence, though lower on SHRA/TS
development and timing.

Increasing VFR cloudiness likely in multiple layers. Can`t rule
out SHRA after 16z anywhere, but prospects for showers increase
after 18-20z largely from ORH westward. Possible rumble of
thunder but SHRA should predominate for the western airports.
Indicated VCSH or SHRA for the western/central airports but left
eastern TAFs dry due to lower prob of SHRA. SW winds increase to
around 8-12 kt, strongest southeast MA.

Tonight: Moderate confidence.

General deterioration expected for most airports with at least
BKN VFR-MVFR bases. Weak low pressure passing thru s`rn CT and
RI/MA South Coast favors 3-6 SM visby SHRA mainly BDL-PVD-Cape
airports on southward starting 01-03z, with best chance at MVFR/IFR
ceilings for these airports. Less certain/lower prob on SHRA
coverage north of this area. SW winds begin to decrease to 5 kt
or less; best chance at mist/fog is largely south of the Mass
Pike.

Friday: Moderate confidence.

Anticipated sub-VFR ceilings more likely for PVD and the South
Coast; it could take some time for these conditions to improve
if they do so at all. Should see BKN VFR ceilings elsewhere,
with possible pop-up SHRA/TS in the aftn hrs; best chance from
ORH westward. S to SE winds under 10 kt.

KBOS TAF...High confidence in TAF. SCT-OVC VFR ceilings through
at least early tonight. Better chance at MVFR bases and -SHRA
after 03z Fri, with improvement toward SCT-BKN VFR after 12z
Fri. SW winds around 10-12 kt today, easing to 5 kt or less
thru late tonight.

KBDL TAF...High confidence in TAF. VFR most of the day, though
risk for SHRA/possible rumble of thunder after 20z Thu until
07z Fri. Sub-VFR possible in this timeframe. SW winds increase
to around 10 kt today, then ease to around 5 kt tonight.

Outlook /Friday Night through Monday/...

Friday Night: Mainly VFR, with areas IFR possible. Chance SHRA,
isolated TSRA.

Saturday: MVFR/IFR conditions possible. Breezy. Chance SHRA,
slight chance TSRA, patchy BR.

Saturday Night: Mainly VFR, with local IFR possible. Breezy.
Chance SHRA, isolated TSRA.

Sunday 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.

Today through Friday: High confidence.

Winds and seas below SCA thresholds. SW winds increase to 10-20
kt today, though decrease a bit into tonight. Scattered
showers/possible t-storms mainly for the southern waters
tonight, with a risk for fog/mist. South winds around 10-15 kt
on Fri. Rain showers may continue into Fri on the southern
waters too, but with lesser coverage.

Seas through the period generally 3 ft or less on all waters.

Outlook /Friday Night through Monday/...

Friday Night: Winds less than 25 kt. Seas locally approaching
5 ft. Slight chance of rain showers.

Saturday: Low risk for Small Craft Advisory winds with gusts up
to 25 kt. Seas up to 5 ft. Slight chance of rain showers.

Saturday Night: Low risk for Small Craft Advisory winds with
gusts up to 20 kt. Seas up to 5 ft. Chance of rain showers,
isolated thunderstorms.

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

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