226
FXUS61 KBOX 070634
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
234 AM EDT Sun Jul 7 2024

.SYNOPSIS...
Aside from a lone shower or thunderstorm, warm and muggy
conditions will persist tonight. Summertime heat and humidity
should prevail next week, along with scattered showers and
thunderstorms, especially Wednesday through Saturday.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
1000 PM Update:

Updated the forecast to nowcast the developing areas of
thunderstorms mainly north of the Mass Pike, carrying scattered
t-storms for those locations thru 2 AM. These storms appear to
be blossoming in response to a sagging sfc trough that trails
from Berkshire County MA into western NH. Mixed-layer CAPE
values still have about 1000-1500 J/kg according to SPC
mesoanalyses, and the forecast suggests this axis of instability
only slowly weakens. Considerable convective inhibition exists
per SPC`s mesoanalysis, and while PSF did measure a 44 mph gust
associated with these storms, it likely will not get worse than
that in any of these storms as they move toward the E/ENE.
Lightning and brief heavy downpours are the main risks
associated with this activity and severe weather is not
expected. It still is unclear what the shower/t-storm risk
looks like for the remainder of the overnight into early
morning; there are some hints that the boundary sags southeast
into the fog/stratus-blanketed southeastern MA and RI and a few
guidance sources show re-developing showers for those
locations. This will need to be carefully evaluated overnight;
wouldn`t entirely rule out thunderstorms for SE MA and RI since
it is so muggy out, but the odds aren`t especially favoring that
outcome. Should be trending drier the further northwest one
goes, with a drop in dewpoints from the mid 70s to the mid to
upper 60s.

The next issue is expanding stratus and fog over at least
eastern CT and areas near and southeast of I-95. It`s a
favorable setting for continued expanding stratus at least
trapped under the inversion, and while we`ve been seeing more
sites report visbys in the 1 to 3 SM range tonight then prior
nights, visby guidance the last couple nights has also
overforecast fog. Will monitor this and if visbys do drop as low
as guidance suggests, we`d consider fog statements for these.

Otherwise, quite muggy out with lows in the mid 70s.

Previous discussion:

Still have a good amount of instability across interior this
evening with MLCAPE as high as 2000 J/kg but airmass shows more
inhibition (CIN) farther east into central/eastern MA, eastern
CT, and RI. Storms have been firing to our west and north and we
are starting to see some new activity developing near
Berkshires. This should be the area to focus on early tonight
where instability is collocated with strong 0-6km shear, but mid
level lapse rates are meager at best which will prevent activity
from becoming more organized. Minor flooding from brief
downpours is main threat but storms are moving along quickly.
High-res guidance continues to struggle with both timing and
location in weakly forced environment.

Otherwise, low cloud bank was spreading inland from RI and SE MA
and should expand farther inland tonight, most likely into
Worcester Hills and more of Merrimack Valley. Patches of dense
fog also expected with persistent SW flow, mainly along and SE
of Providence to Plymouth line.

Warm and muggy night is in store with lows in upper 60s and 70s.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM MONDAY/...
A front slowly sags into southern New England late tonight into
Sunday. Not much push behind this front, so thinking this front
is still lingering nearby into Sunday night, most likely toward
the coast.

Very humid conditions and above normal temperatures continue.
That said, a subtle intrusion of drier air in the mid levels
aloft should provide more of a cap on showers and thunderstorms
during this time.

&&

.LONG TERM /MONDAY NIGHT THROUGH SATURDAY/...
Highlights:

 * Summertime heat and humidity most of next week - potential
   Heat Advisory for some Mon/Tue
 * Scattered showers/storms mainly Wed-Fri

Ensembles are in good agreement next week and feature persistent
subtropical ridge over the western Atlantic and upper trough
near Great Lakes. This pattern favors typical summertime heat
and humidity as SW flow aloft transports very warm and humid air
up the East Coast.

Core of heat and humidity looks to be Mon/Tue. We could reach
Heat Advisory criteria (heat index 95-99F for 2 or more hours
on consecutive days) away from coast and especially in the
Connecticut and Merrimack Valleys as well as interior eastern
MA. For rest of next week, presence of more cloud cover should
keep highs in 80s, but overnight lows will probably stay in 70s,
especially in urban areas.

As we`ve seen over the past week, there probably won`t be a lot
of larger scale forcing present to result in organized showers
or thunderstorms. Rather, we should see weaker short waves from
Great Lakes dampen out as they run into upper ridge offshore.
Timing of these short waves is always a problem in the model
world, especially at longer time ranges, but it does appear our
better chances of showers/storms will be in the Wed-Sat
timeframe (afternoon and evening) as we also have weak surface
fronts nearby.

&&

.AVIATION /06Z SUNDAY THROUGH THURSDAY/...
Forecast Confidence Levels:

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

06z TAF Update:

Through 12z Sunday: High confidence.

IFR to LIFR from stratus and fog. These conditions should remain
steady thru 12z for most, though we should start to see
improvement around after 10z Sunday for the western airports.
Light/calm winds north and west of I-95, otherwise southerly
winds 5-10 kt.

Today: High confidence overall, though moderate on timing
sub-VFR improvement.

IFR-LIFR to slowly improve to VFR for most thru 15z, with fog
retreating into the waters. IFR-LIFR is expected all day for the
South Coast, Cape and Islands. A chance for isolated/widely
scattered TS after 18z to sundown near I-95 with best chance at
PVD, but could slip as far north as ORH and BOS. Sub-VFR stratus
then starts to return northward slightly very late in the
period. Light W/WNW winds north and west of I-95, with
seabreezes at BOS as conditions trend VFR. SSW winds 5-10 kt for
PVD, Cape and Islands.

Tonight and Monday: Moderate confidence.

IFR-LIFR fog and stratus from the daytime hrs over the south
coast, Cape and Islands returns northward tonight; best chance
for PVD and the Cape/ACK, though it is possible it could slip
northward into the BOS-ORH-BDL areas. Where it does develop,
improvement should take place Monday morning, soonest north and
west and later/afternoon towards the southeast coast. Light
winds tonight and Monday, with seabreezes at BOS and PVD.

KBOS TAF...High confidence in TAF. IFR-MVFR stratus and fog
should improve to VFR by ~12-15z. VFR thereafter with
seabreezes likely to develop. Low (< 15%) chance at SHRA/TS
after 18z til sundown but best chance to the south. Stratus is
possible again after 04z Mon, but better chance southeast.

KBDL TAF...High confidence in TAF. IFR to improve to VFR by
10-12z Sunday. Stratus could return after 02z Mon but better
chance southeast.

Outlook /Monday Night through Thursday/...

Monday through Monday Night: VFR.

Tuesday: VFR. Slight chance SHRA, isolated TSRA.

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

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

Wednesday Night: VFR. Chance SHRA.

Thursday: VFR. Chance SHRA, isolated TSRA.

&&

.MARINE...
Forecaster Confidence Levels:

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

Through Sunday Night:

S to SW flow continues as a front slowly approaches the waters
tonight, then likely stalls across the waters Sunday into Sunday
night. A few gusts up to 25 kt, along with marginal 5-foot seas
across the southern coastal waters, so continued the Small Craft
Advisories into Sunday. Areas of fog may reduce visibility below
1 mile late tonight. Visibility expected to improve Sunday.

Outlook /Monday Night through Thursday/...

Monday through Tuesday: Winds less than 25 kt.

Tuesday Night: Winds less than 25 kt. Slight chance of rain
showers, isolated thunderstorms.

Wednesday: Winds less than 25 kt. Chance of rain showers,
isolated thunderstorms.

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

&&

.BOX WATCHES/WARNINGS/ADVISORIES...
CT...None.
MA...None.
RI...None.
MARINE...Small Craft Advisory until 8 AM EDT this morning for ANZ254.
     Small Craft Advisory until 11 AM EDT this morning for ANZ255-
     256.

&&

$$

SYNOPSIS...Belk/JWD
NEAR TERM...Belk/Loconto/JWD
SHORT TERM...Belk
LONG TERM...JWD
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley