983
FXUS61 KBOX 020509
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
109 AM EDT Tue Jul 2 2024

.SYNOPSIS...
Clearing tonight with cooler than normal temperatures as high
pres builds in from the west. The high pressure brings dry
weather and seasonably warm temperatures with comfortable
humidity for Tuesday and Wednesday. Turning more humid and
unsettled for Independence Day into this weekend with a couple
of disturbances offering chances for showers and thunderstorms.

&&

.NEAR TERM /THROUGH TODAY/...
A sprawling, seasonably-strong 1024 mb high pressure cell was
located near Rochester NY early this morning, and ridging from it
was extending eastward into Southern New England. Tranquil
conditions with dewpoints falling thru the 50s for most. Some
patches of fog but these should be dissipating shortly after
sunrise.

Shaping up to be an outstanding early-July day for Southern New
England, as the aforementioned high pressure area ridges eastward.
Wall to wall sun today from the beaches to the Berkshires and points
in between today, with comfortable humidity levels. Should see
cirrus clouds start to overspread very late in the day but that`s
about it. Modest northerly wind this morning subsides with
slackening pressure gradient, and winds by late morning into the
aftn become driven by mesoscale effects (terrain and
seabreezes). Highs in the low to mid 80s for most, with mid to
upper 70s near the coasts with anticipated seabreezes.

&&

.SHORT TERM /TONIGHT THROUGH 6 PM WEDNESDAY/...
High pressure expected to open tonight over eastern NY to
shift SE thru tonight into the southern offshore waters and
generally maintain that position through Wed. Thus continued
tranquil weather is expected both tonight and Wednesday,
although will see periods of high clouds spill into Southern New
England.

The question mark for tonight is on potential for patchy
radiation fog at least in the river valleys. We do get into a
modest southerly flow late tonight and that should bring
dewpoints up somewhat (into the mid/upper 50s). Models for
tonight seem pretty mixed on the potential and also is not really
hinted at in the MOS progs either, but it seems like one of
those nights where you could get at least river valley fog to
develop with good radiational cooling expected. MOS used for
lows in given radiational cooling, with lows in the 50s for
most, though the urban areas and hills could see readings near
60.

Modest southerly gradient expected for Wed, but think weak flow
aloft should again favor seabreezes on both coasts. More of a mix of
sun and high clouds for Wed, along with dewpoints rising to near 60
so humidity levels should be tolerable. Highs in the 80s, with late-
day highs on the eastern MA coast once seabreeze-driven winds shift
to the SW.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH MONDAY/...
Key Points...

* Dry and warm with tolerable humidity levels for Wed.

* Turning more humid and active for Independence Day, and
  potentially into Fri/Sat too, with clouds, showers and storms
  possible. Exact timing remains uncertain.

Details...

Mid level ridging with surface high pressure continues to dominate
the sensible weather through mid week bringing dry and increasingly
humid weather on Wednesday. A shift then occurs for the latter half
of the week into the weekend as zonal flow returns accompanied by
periodic but increasingly strong shortwave disturbances. The first of
these disturbances will move through on Independence Day as a trough
of low pressure over Canada slides through New England. This will
provide some marginal synoptic scale lift which along with a weak
warm front lifting north may be able to kick off some scattered
showers overnight and into Independence Day. The best chance of
seeing a shower or thunderstorm will be over northern MA, furthest
removed from the suppressive effects of high pressure to our south.
A cold front then moves through around late Thursday/early Friday
which will provide a better source of lift for some showers or
thunderstorms. Too soon to say who will see a downpour or t-storm
but as we get into the range of more high-res guidance, instability
(while not excessive) is is concentrated over the high
terrain/interior suggesting the best chance of t-storms there. Any
storms are unlikely to become severe given lack of bulk shear and
marginal lapse rates, though things can change as we get closer. The
chance for unsettled weather further increases on Friday into the
weekend as the front moves north again as a warm front returning
more humidity and instability to the region ahead of a deeper trough.
It doesn`t look like we`ll get a break in the rain/storm chances
until around Monday when a drier post frontal airmass may arrive but
confidence is low.

&&

.AVIATION /06Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

06z TAF Update:

Today through Wednesday: High confidence.

VFR for all airports through the period. Winds today start light
northerly (4-8 kt), with seabreezes developing 15-17z on both
coasts. Winds then turn light southerly tonight and overnight,
which continue into Wednesday as well. Another period of
seabreezes expected on Wed on both coasts following a roughly
similar timeframe of onset and cessation.

KBOS TAF...High confidence in TAF. VFR thru the period. NW
winds around 4-8 kt to start ease and shift to seabreezes/ESEly
around 8-10 kt ~15-17z thru 23z-00z, then begin a clockwise
turn to NW for overnight. Another period of seabreezes for Wed.

KBDL TAF...High confidence in TAF. VFR thru the period. N winds
around 5-8 kt today, but shift to light southerly late today
which continue into Wed.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: VFR. Slight chance SHRA.

Independence Day: VFR. Breezy. Slight chance SHRA.

Thursday Night through Friday Night: VFR. Slight chance SHRA.

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

&&

.MARINE...
Forecaster Confidence Levels:

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

Generally pleasant marine weather conditions as broad high pressure
gradually builds into the waters by Wed. Northerly winds this
morning around 10-15 kt to steadily decrease this afternoon
(becoming ESE near the immediate eastern MA coast), then begin to
shift to light SW late in the overnight hrs. Light SSW winds for
Wed, with local ESE winds near the immediate shorelines for Wed.
Seas 3 ft or less all waters.

Outlook /Wednesday Night through Saturday/...

Wednesday Night: Winds less than 25 kt.

Independence Day through Saturday: Winds less than 25 kt.
Slight chance of rain showers.

&&

.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