655
FXUS61 KBOX 041721
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
121 PM EDT Thu Jul 4 2024

.SYNOPSIS...

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.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...

930 AM Update...

* Considerable clouds with peeks of sunshine at times along with
  increasing humidity & highs in the 80s

* A few showers perhaps an isolated t-storm later today...mainly
  across the interior but dry weather dominates

Considerable mid-level cloudiness covered the region at mid-
morning...but there were peeks of sunshine too. High pressure
off the coast will continue to generate a southwest flow of
increasing humid air into the region. Despite the considerable
cloudiness...expect enough peeks of sun for highs to reach into
the middle 80s away from the south coast where upper 70s to the
lower 80s more common. It is even possible a few spots reach
the upper 80s if enough solar insolation can be realized.
Dewpoints rising through the 60s will result in increasing
humidity through the day.

Dry weather dominates today...but enough diurnal heating
combined with a weakening shortwave will probably be enough to
trigger a few showers and perhaps an isolated t-storm or two
mid to late this afternoon into early this evening. This will
mainly across interior southern New England as the shortwave
will tend to weaken as it encounters mid level ridging. But
regardless...the main story is dry weather dominating.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...

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.

&&

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

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.

&&

.AVIATION /17Z THURSDAY THROUGH MONDAY/...

Forecast Confidence Levels:

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

18z TAF Update...

This afternoon and tonight...High Confidence.

VFR into the evening hours with mainly just mid level
cloudiness. We do expect MVFR-IFR ceilings to begin to develop
after midnight as the boundary layer cools and low level
moisture continues to increase. A few showers perhaps an
isolated t-storm possible later this afternoon into this evening
across the interior. Greater risk for more scattered showers and
perhaps a rumble of thunder will be after midnight. Any of this
activity will be capable of producing brief downpours. S-SW
winds 5-15 knots becoming light tonight.

Friday and Friday night...Moderate Confidence.

MVFR-IFR conditions early Fri morning should improve to mainly
VFR levels by mid afternoon. However...do expect MVFR-IFR
conditions to redevelop Fri night with even some localized LIFR
Cigs/Vsbys. A few showers and perhaps an isolated t-storm or two
will be possible into mid-morning Fri & some re-development is
possible Fri PM. Any of this activity will be capable of
producing brief downpours. Timing/location of this activity is
quite uncertain...but regardless thinking dry weather dominates
the vast majority of the time. S winds mainly 5-10 knots.

KBOS TAF...High confidence in TAF into this evening followed by
moderate confidence thereafter. Main concern is the timing of
the low clouds overnight into Fri am.

KBDL TAF...High confidence in TAF into this evening followed by
moderate confidence thereafter. Main concern is the timing of
the low clouds overnight into Fri am.

Outlook /Saturday through Monday/...

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.

&&

.MARINE...
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.

&&

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

&&

$$

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