790
FXUS61 KBOX 101410
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1010 AM EDT Mon Jun 10 2024

.SYNOPSIS...
Seasonable temperatures today and Tuesday with just a low risk
for a few spot, brief, light showers. A warming and drying
trend Wednesday and Thursday will lead to increasing heat and
humidity on Friday. An approaching cold front will bring an
increasing risk for showers and thunderstorms Friday, followed
by drier and more seasonable temperatures next weekend.

&&

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

10 AM update...

Not much change to previous forecast. Beautiful morning in
progress, with abundant sunshine, dew pts in the upper 40s and
lower 50s, along with temps warming through the 60s. Very
pleasant for June 10th. This is courtesy of a departing short
wave east of Massachusetts, with subsidence on the backside
across SNE this morning.

By afternoon, the mid/upper level flow across SNE becomes more
cyclonic and this will allow SCT to BKN diurnal clouds to
develop. This combined with cool air aloft, may be sufficient
for a few brief, isolated and light showers. However, given low
dew points, cloud bases will be fairly high (6-8kft), with dry
air below cloud level, hence, some virga is likely. Thus, a
mainly dry and beautiful afternoon ahead. Therefore, no changes
with this update. Earlier discussion below.

==================================================================

Mid level shortwave across SNE will move off the coast by
daybreak. Subsidence and drying behind this shortwave will bring
abundant sunshine this morning, but sct-bkn diurnal CU will
develop late this morning through the afternoon as steep low
level lapse rates act on shallow moisture at the top of the
boundary layer. Another weak shortwave will be moving south from
northern NY and VT this afternoon and can`t rule out a few spot
showers developing, but expect mostly dry weather. 850 mb temps
8-9C support highs in the mid-upper 70s, and humidity levels
will be rather low as mixing will result in dewpoints in the
upper 40s and lower 50s. Modest west breezes today becoming SW
near the south coast.

&&

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

Tonight...

Mid level trough axis will be across New Eng, but cooling boundary
layer will stabilize low levels and dry conditions expected.
Lingering moisture in the 850-700 mb layer will keep some cloud
cover around but not completely cloudy allowing for modest
radiational cooling as winds become light. It will be a cool night
with lows dropping to the low-mid 50s, with upper 40s higher
terrain.

Tuesday...

Pretty similar conditions to today as mid level trough and colder
air aloft will be across the region. This will lead to steep low
level lapse rates and sct-bkn CU developing and can`t rule out a few
spot showers developing again during the afternoon. Not much change
in low level temps so highs will be in the mid-upper 70s again,
although sea-breezes are more likely given a lighter wind
field, which will keep coastal locations a bit cooler.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...

Highlights:

* Temperatures on the uptick Wednesday through Friday

* Cold front crossing the region late week may trigger a few
  thunderstorms late Friday into early Saturday

* Weekend looking dry with temperatures slightly above normal

A 500 hPa upper-level low becomes centered over southern New England
on Wednesday. Temperatures will continue to hover in the near-normal
range with highs in the mid 70s. Some modest instability may support
a few spot showers or thunderstorms Tuesday afternoon, but any
convection would be battling an environment with little forcing,
limited moisture, and almost no wind shear. Thus, any showers or
storms on Tuesday would be expected to be short-lived.

Wednesday

Upper-level low slowly lifts northeast on Wednesday. This will
support height rises over southern New England for much of the day
which should support a good amount of sunshine. Colder air aloft
will continue to support fairly steep lapse rates during the
afternoon, so some diurnal clouds and possibly a spot showers can`t
be ruled out. Otherwise expect comfortable conditions with highs in
the upper 70s to low 80s and low humidity.

Thursday and Friday

Deep southwest flow takes control on Thursday which will begin an
uptick in temperatures across southern New England. 925 hPa temps
right to near 20 Celsius which should support surface high temps in
the mid to upper 80s F. Heights continue to rise with mid-level
ridging, so expect plenty of sunshine on Thursday. Southwest flow
will also allow dewpoints to creep up bit, reaching the low 60s for
some locations in southeast MA, but dewpoint depressions should be
high enough that the humidity won`t be uncomfortable.

Southwest flow increases on Friday as the pressure gradient tightens
in response to an approaching cold front. Models have trended toward
a later arrival of this front over the last 48 hours, with the FROPA
more likely to be Friday evening than Friday afternoon. This portion
of the forecast will require careful monitoring as increasing
southwesterly flow will come with increasing humidity as dewpoints
rise into the mid to perhaps upper 60 with an enhanced region of
integrated water vapor transport overhead. During an afternoon
where highs are expected to reach the upper 80s across much of
southern New England, this would support an unstable atmosphere with
some models hinting at MLCAPE values between 500 and 1000 J/kg. The
wind field accompanying the frontal passage looks to be fairly
strong for mid-June as well with deep layer shear ranging from 30 to
40 knots Thus, we`d have all the ingredients in place for severe
thunderstorm potential. The X-factor will be the timing of the
frontal passage. If it arrives in time to take advantage of the
diurnal instability, then Friday afternoon/evening may be active.
However, if models continue to trend toward a layer arrival of the
cold front, then a more modest round of showers with embedded
thunder would be in the cards for Friday night/early Saturday. We`ll
have more details by mid-week.

Saturday and Sunday

Some showers possibly early Saturday depending on the timing of the
aforementioned cold frontal passage. Behind the front however, we
would expect rapid clearing and a drier air mass that will support a
pleasant Father`s Day weekend. Temps look to be slightly above
normal in the upper 70s to low 80s with the drier air mass
supporting plenty of sunshine. Always take the day 7 forecast with a
grain of salt, but as of this time, next weekend looks to be quiet
after the frontal passage.

&&

.AVIATION /14Z MONDAY THROUGH FRIDAY/...
Forecast Confidence Levels:

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

15Z TAF Update: Not much to add from previous forecast update,
VFR cloud bases this afternoon with perhaps an isolated, brief,
light shower. Much if not all the activity will struggle to
reach the ground given the dry low level air. Therefore,
thinking most if not all runways remain dry today. Should be
enough of a west wind 10-15 kt, gusting up to 20 kt at times, to
offset any potential seabreeze. Earlier discussion below.

=================================================================

Today: High confidence.

VFR, with sct-bkn CU developing by late morning. A spot shower
is possible in the afternoon. W wind around 10 kt with gusts to
15-20 kt, becoming SW along the south coast.

Tonight: High confidence.

VFR. Light to calm winds.

Tuesday: High confidence.

VFR, with sct-bkn CU developing with a few hit-or-miss showers
possible in the afternoon. W wind 5-10 kt with sea-breezes
developing along the coast.

KBOS TAF...High confidence. There should be just enough W
wind to keep the sea-breeze offshore. However, if winds end up
a bit lighter, a weak sea-breeze is possible this afternoon.

KBDL TAF...High confidence.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Thursday Night: VFR.

Friday: VFR. Breezy. Chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

High confidence through Tuesday.

SW winds gusting up to 20 kt over the south coastal waters today
with lighter S winds over NE MA waters. Tranquil boating conditions
tonight and Tue with light winds and seas. Winds shift to NW later
tonight behind a weak front, then becoming SE-SW Tue afternoon as
sea-breezes develop.

Outlook /Tuesday Night through Friday/...

Tuesday Night through Thursday: Winds less than 25 kt.

Thursday Night: Winds less than 25 kt. Seas locally approaching
5 ft.

Friday: Low risk for Small Craft Advisory winds with gusts up
to 20 kt. Seas up to 5 ft. Slight chance of rain showers.

&&

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

&&

$$

SYNOPSIS...KJC/RM
NEAR TERM...KJC/Nocera
SHORT TERM...KJC
LONG TERM...RM
AVIATION...KJC/Nocera/RM
MARINE...KJC/RM