239
FXUS61 KBOX 030610
AFDBOX

Area Forecast Discussion
National Weather Service Boston/Norton MA
210 AM EDT Wed Jul 3 2024

.SYNOPSIS...
High pressure will bring another beautiful day of weather on
Wednesday with comfortable humidity. A typical summertime
pattern will set up from the 4th of July through early next week
with very warm and humid conditions. There will be a risk of a
few showers and t-storms at times through the period but most of
the time will likely be dry.

&&

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

High pressure now over northern Providence County leading to
temps falling into the lower to mid 60s over southeast New
England, but are a little warmer in interior MA/CT where current
readings are still in the upper 60s to low 70s. Brought temps up
a few degrees through 1 AM in western locations; we should still
see strong radiational cooling take place in most areas, even
with a stream of cirrus cloudiness moving in, so kept lows
unchanged. Dewpoints are also a little higher than last night in
the mid to upper 50s, so we could have to watch for patchy
radiation fog in the typical prone locations, but also in
southeast MA where temperature/dewpoint spreads are narrower.

Previous discussion:

305 PM Update...

* Mainly clear tonight other than some high clouds
* Cool with lows mainly in the 50s to lower-middle 60s urban centers

Large high pressure will remain in control of our weather tonight.
This will result in calm/light winds and a very good night of
radiational cooling given the dry airmass in place for July
standards. Model cross sections do indicate a bit of high cloudiness
may spill into the region from the northwest overnight...but it
should not have a significant impact on temps. Low temps should
bottom out between 50 and 55 in the normally coolest outlying
locations...to the lower to middle 60s in the urban heat islands of
Boston/Providence.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM THURSDAY/...
Key Points...

* Plenty of sunshine Wed with highs mainly in the middle-upper 80s
* Not as cool Wed night with lows in the lower-middle 60s

Details...

Wednesday...

High pressure slowly slides east of the region...but will remain in
control of our weather. So while we will see some mid-level
cloudiness...expect plenty of sunshine. This should result in high
temps Wed mainly in the middle to upper 80s. Dewpoints should remain
in the 50s...so still a very comfortable day for early July.

Wednesday night...

High pressure will continue to move further east and away from the
region. At the same time...a mid level warm front will approach from
the west. This should result in some clouds overspreading the region
after midnight with even a few spot showers possible across the
interior toward daybreak Thu. Low temps will only drop into the
lower to middle 60s...so quite a bit milder than tonight.

&&

.LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/...
Key Points...

* Above normal temps and elevated humidity from 4th of July through
  early next week

* Some risk for a few showers or t-storms through early next week
  but dry weather most of the time

Thursday and Friday...

Mid level ridge will get shunted to the south as northern stream
shortwave energy passes well to the north. This results in a quasi-
zonal flow with a couple weak shortwaves moving north of the region.
Not much instability on Thu with limited large scale forcing so just
a low risk for a few showers in western New Eng closest to
instability axis to the west, otherwise dry. Then on Friday, a bit
more instability but limited forcing again so while we can`t rule
out a few showers or a t-storm, much of the day should be dry. Any
convection Friday would be favored near the south coast where
elevated PWAT axis is located. It will be warm and humid with highs
in the 80s and dewpoints climbing to near 70.

Saturday through Tuesday...

SNE will be on the western periphery of the Atlantic sub-tropical
ridge while a series of mid level shortwaves move through the Gt
Lakes. This will result in SW flow aloft with pulses of high PWATs
surging into the region so can`t rule out a few instances of
convection, but timing and areal coverage is very much uncertain
given weak forcing regime. One de-amplifying shortwave lifts NE from
the Gt Lakes Sat with anomalous PWATs up to 2.25" moving into SNE.
The Sat to Sat night period may be be the best chance for scattered
showers/t-storms as weak front approaches from the west. Overall a
very warm and humid period as 850 mb temps average 16-19C. Highs
will be well into the 80s, with a few 90 degree readings in the
interior, but a bit cooler south coast. Sat will be especially humid
with dewpoints approaching the mid 70s.

&&

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

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

06z TAF Update:

Through 12z Wednesday: High confidence.

VFR. Patchy BR possible for southeast MA airports thru 12z but
should be brief/dissipating shortly after sunrise. Light south
winds, calm at times.

Today: High confidence.

VFR. SW to S winds around 5-10 kt, though seabreezes for BOS
and PVD. BOS should start to see SE sea breezes around 14-15z
and PVD around 17-19z.

Tonight: High confidence overall, though moderate on fog
coverage and timing.

Increasing VFR cloudiness for most. As moisture levels start to
rise after 04z Thu, we should see developing MVFR-LIFR fog over
the southern waters, then expanding slightly landward. Areas
most at risk are ACK, Cape airports and perhaps as far north as
PVD. Could see a hit or miss shower after 06z Thu at BAF-BDL
but should be largely dry. SW winds around 6-12 kt.

Thursday/Independence Day: High confidence.

Fog on the south coast should dissipate by 13z Thu. As a weak
front moves through, cloud cover increases toward a multi-
layered VFR look, though can`t rule out a BKN030 layer sneaking
in at times. SCT SHRA possible, best chance SW of ORH but dry
weather prevails most of the time. SW winds increase to around
10-15 kt with gusts 20-22 kt for southeast MA airports.

KBOS TAF...High confidence in TAF. VFR through the TAF period.
Seabreezes expected today and it could develop early (as soon
as 14z?) but more probable by 15z. Winds then turn SSW around
10 kt around 00z Thu thru rest of the TAF period.

KBDL TAF...High confidence in TAF. VFR thru the TAF period.
Light winds initially turn S around 4-8 kt today, then increase
to around 10 kt tonight. Increasing cloudiness tonight with a
chance for a shower but somewhat better chances on Thu.

Outlook /Thursday Night through Sunday/...

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

Thursday Night: VFR. Slight chance SHRA, isolated TSRA.

Friday: VFR. Slight chance SHRA.

Friday Night: Mainly VFR, with local MVFR possible. Slight
chance SHRA.

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

Saturday Night: Mainly VFR, with areas IFR possible. Breezy.
Chance SHRA, isolated TSRA.

Sunday: 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.

Tonight through Wednesday night...High Confidence.

High pressure over the waters tonight slowly shift to the east Wed
and Wed night. Light winds tonight will become SSW at 10 to 15 knots
Wed into Wed night with a few gusts up to 20 knots. However...the
pressure gradient should remain weak enough to keep winds/seas below
small craft advisory levels.

Outlook /Thursday Night through Sunday/...

Independence Day: Winds less than 25 kt.

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

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

Saturday Night through Sunday: Winds less than 25 kt. Areas of
seas approaching 5 ft. Chance of rain showers, isolated
thunderstorms.

&&

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

&&

$$

SYNOPSIS...KJC/Frank
NEAR TERM...Frank/Loconto
SHORT TERM...Frank
LONG TERM...KJC
AVIATION...Loconto/Dooley
MARINE...Loconto/Dooley