879
FXUS61 KBOX 012331
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
731 PM EDT Mon Jul 1 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 /UNTIL 6 AM TUESDAY MORNING/...
Impressive shortwave and accompanying cold pool aloft with 500 mb
temps down to -18C across SNE this afternoon leading to steep low
and mid level lapse rates. Scattered to numerous showers and
isolated thunder focused along a convergence zone near the I-95
corridor from NE MA into RI. This activity will begin to diminish by
mid-late afternoon as the trough axis and cold pool begin to shift
to the east. Rising heights tonight as high pres builds in from the
west will lead to clearing skies and a relatively chilly night by
early July standards. Still enough pressure gradient for a modest N
breeze but winds will diminish enough for lows to drop into the 50s,
with some upper 40s not out of the question in some of the cooler
spots in western MA. Lows will likely remain above 60 over the outer
Cape, ACK and Boston metro.

&&

.SHORT TERM /6 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Tuesday...

Spectacular early summer day as high pres builds into the region.
The high will bring abundant sunshine with warm temps, light winds
and low humidity. Highs will reach the low-mid 80s with dewpoints
well down into the 50s. Light wind field will promote coastal sea-
breezes which may keep temps in the upper 70s along the immediate
coast.

Tuesday night...

High pres remains in control with dry weather and light to calm
winds. A weak shortwave coming over the ridge will bring some high
clouds to the region but not enough to significantly impact low
temps. Blended the NBM guidance with cooler MOS to derive low temps
which yields lows in the 50s.

&&

.LONG TERM /WEDNESDAY 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 /00Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

Tonight through Tuesday night...High confidence.

VFR. Diminishing N wind tonight with sea-breezes developing Tue
along the coast.

KBOS TAF...High confidence.

KBDL TAF...High confidence.

Outlook /Wednesday through Saturday/...

Wednesday: VFR.

Wednesday Night: VFR. Slight chance SHRA.

Independence Day: VFR. Breezy. Slight chance SHRA, isolated
TSRA.

Thursday Night through Friday: VFR. Slight chance SHRA.

Friday Night: VFR. 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.

Winds and seas below SCA thresholds tonight through Tue night.
Diminishing N winds tonight with speeds lowering to 10-15 kt
with light E-NE winds Tue and light W-NW winds Tue night.
Scattered showers and isolated t-storm over south coastal
waters diminishing by this evening, otherwise dry weather with
good vsbys through Tue night.

Outlook /Wednesday through Saturday/...

Wednesday through Wednesday Night: Winds less than 25 kt.

Independence Day through Thursday Night: Winds less than 25 kt.
Seas locally approaching 5 ft. Slight chance of rain showers.

Friday through Friday Night: Winds less than 25 kt. Slight
chance of rain showers.

Saturday: Winds less than 25 kt. Seas locally approaching 5 ft.
Chance of rain showers, isolated thunderstorms.

&&

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

&&

$$

SYNOPSIS...KJC/BW
NEAR TERM...KJC
SHORT TERM...KJC
LONG TERM...BW
AVIATION...KJC/BW
MARINE...KJC/BW