127
FXUS61 KBOX 040207
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
1007 PM EDT Mon Jun 3 2024

.SYNOPSIS...
A back door cold front will push south from Maine and usher in
cooler weather tonight and Tuesday, especially near the coast.
Our weather pattern then changes to a cloudy and more unsettled
outlook by Thursday and into the weekend. Thursday looks to be
the wettest day with showers and storms capable of localized
downpours, with more hit or miss showers or thunderstorms for
Friday into the weekend. Temperatures trend a little cooler
than normal.

&&

.NEAR TERM /UNTIL 7 AM TUESDAY MORNING/...
10 PM update...

Weak backdoor front pushing west across SNE and will move
through CT valley overnight as surface ridging builds south
from Maine. Light E winds will develop after the front moves
through. We have some mid level clouds developing across eastern
MA, while area of stratus over the ocean east of Cape Cod is
expanding west. As the land and marine boundary layer cools
off, these lower clouds will eventually overspread Cape Cod and
expand west into eastern MA and RI overnight. It still is a
bit unclear how far west this stratus makes it; it could bleed
over into central MA and eastern CT at worst but likely not any
further given the weaker lower level flow. Radiational cooling
has resulted in temps dropping into the 50s across SE MA. Lows
will range from lower 50s over SE MA and Cape/Islands to upper
50s to around 60 in the CT valley.

&&

.SHORT TERM /7 AM TUESDAY MORNING THROUGH TUESDAY NIGHT/...
Fairly quiet weather as upper ridge remains west of New England
and weak high pressure builds in at surface.

Low clouds and patchy fog should lift quickly as moisture will
be fairly shallow and high June sun angle goes to work. It
should take the longest near Cape Cod and Islands where this
marine layer will be deepest, but even these areas should clear
out by late morning.

Not seeing a lot of good signals for afternoon convection as
what instability there is stays to our west, or at most is tied
to higher terrain areas near Berkshires. Low and mid level lapse
rates are not overly impressive and we remain under large scale
subsidence on eastern side of ridge. Nonetheless, we can`t rule
out a spot shower/storm Tue afternoon near Berkshires. Onshore
winds will keep highs in 60s/lower 70s near immediate coast but
inland areas should have no problem warming well into 80s.
Airmass remains fairly dry which will help temperatures fall
back into 50s Tue night.

&&

.LONG TERM /WEDNESDAY THROUGH MONDAY/...
Highlights:

* Pattern change toward wetter conditions and temps trending
  somewhat cooler than normal Thurs thru the weekend.

* Wettest day looks to be Thurs with local downpours possible. More
  hit or miss showers and t-storms for Fri into the weekend.
  Possible isolated hydro issues but significant flooding not
  expected.

Details:

Wednesday:

Wed projects as the final generally dry day for Southern New England
as we head into a cloudy and soggy weather pattern for late week
into the weekend. 500 mb heights weaken slightly and though that
could support a low chance (under 20% PoP) for an afternoon shower
or t-shower over northern/western MA, dry weather should result for
the vast majority of the time. Increasing cloud cover for Wed night
along with rising humidity levels (dewpoints into the lower-mid
60s), with a rise in PoP toward daybreak into the solid Chance
range, although the bulk of the rains arrive on Thurs. As dewpoints
rise, we could also see a risk for marine fog develop over the
waters. Wed also to be the warmest day under full sun, with highs
well into the 70s to lower-mid 80s, with lower 70s along the south
coast. Lows in the low to mid 60s.

Thursday through the Weekend:

Heading into a period of unsettled weather with several
opportunities for showers and t-storms starting Thurs into
potentially a good portion of the weekend. An upper level closed low
over the Gt Lakes slowly builds into the Northeast for Thurs into
Fri, and remains in place through at least Sat and potentially into
Sunday as well. Though this expected rain should be welcome news to
wash out the clouds of pollen around our area of late, although far
from ideal weather for outdoor plans.

Wettest period still looks to be on Thurs; PWAT values of 1.2 to 1.4
inches along with warm cloud depths between 10000-11000 ft favor
localized downpours in showers and embedded t-storms. Severe weather
potential appears to be low at this time with limited instability
and a general lack of stronger surface heating through abundant
cloud cover. From a hydro perspective, we can`t rule out isolated
issues but probably not anything more than that given the
progressive nature to the rain, and we`ve also been pretty dry of
late. While the international guidance lends support to this
solution, did note the past couple cycles (06/12z) of the
deterministic GFS are cloudy but depict a dry weather pattern.
However there`s a good majority of GFS ensemble members which show
rain for Thurs so we view this as a dry outlier outcome as of now.
NBM probs of 24 hr rain for Thurs have increased into the the
moderate to high (40-60%) range for totals at or above 0.5 inches
for much of the area, and indicate moderate (30-40%) probs for rain
totals at or over 1 inch in portions of RI and SE MA. PoPs were
raised into the high Likely range and Categorical PoP could be
warranted in later updates.

For Fri into the weekend, the upper level low parks itself over or
in the vicinity of Southern New England. This will maintain
cloudier/unsettled weather conditions with more periodic/hit-or-miss
showers or t-storms. Felt NBM based PoPs in the 30-50% range were a
little too high and opted to following a more diurnal approach Fri
into Sunday, with higher PoP during the daytime and lower (20-25%)
at night. Here too, severe weather potential looks on the low side.

Temperatures trend a little cooler than normal for this period, with
cloudy weather and periods of rain, along with 850 mb temps in the
upper single digits to low teens C range. Highs mainly in the lower
to middle 70s and lows in the upper 50s to mid 60s. Though it will
be cooler, humidity levels still looks somewhat elevated.

&&

.AVIATION /02Z TUESDAY THROUGH SATURDAY/...
Forecast Confidence Levels:

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

00z TAFs: High confidence.

Continued VFR through at least 03z Tue. Low clouds then
develop/move onshore over Cape Cod and ACK initially, then
expand a bit further landward into BOS/PVD, BED and perhaps into
ORH early Tue AM. These lower ceilings slowly lift Tue morning
with VFR conditions returning by midday. E/NE winds prevail.

For the inland terminals, VFR through Tue night. Light winds
tonight become S/SE Tue.

KBOS TAF... High confidence (60%). MVFR ceilings most likely to
affect terminal 08z-11z, with scattering out to VFR occurring
by 13z..

KBDL TAF... High confidence (80%). VFR with light and variable
winds tonight, becoming light southerly Tue.

Outlook /Wednesday through Saturday/...

Wednesday: VFR.

Wednesday Night: Mainly VFR, with local IFR possible. Chance
SHRA.

Thursday: Mainly MVFR, with local IFR possible. Breezy. SHRA
likely, isolated TSRA.

Thursday Night: MVFR/IFR conditions possible. Chance SHRA,
isolated TSRA.

Friday and Saturday: Mainly VFR, with areas 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.

Confidence:
 * High (80%) through Tue night. No marine headlines anticipated
   on MA/RI coastal waters with overall light winds and calm
   seas.
 * In the longer range, confidence is high (60%) in upcoming
   pattern which could bring building seas near 5 ft offshore by
   the end of the week.

Backdoor front drops south across waters this evening and
dissipates south of New England tonight, followed by weak high
pressure Tue. This maintains E/NE winds which remain light
enough to maintain fairly calm seas. Should see patchy fog later
tonight into Tue morning with local restrictions in visibility
to 1-3 miles.

Winds veer to S/SW Tue as high moves offshore but weak enough to
allow for coastal sea breezes again by afternoon.

Outlook /Wednesday through Saturday/...

Wednesday: Winds less than 25 kt.

Wednesday Night: Winds less than 25 kt. Chance of rain showers.

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

Thursday Night through Saturday: Winds less than 25 kt. Seas up
to 5 ft. Chance of rain showers.

&&

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

&&

$$

SYNOPSIS...Loconto
NEAR TERM...KJC/Loconto
SHORT TERM...JWD
LONG TERM...Loconto
AVIATION...Loconto/JWD
MARINE...Loconto/JWD